diff --git a/libcxx/benchmarks/lit.cfg.py b/libcxx/benchmarks/lit.cfg.py
--- a/libcxx/benchmarks/lit.cfg.py
+++ b/libcxx/benchmarks/lit.cfg.py
@@ -3,21 +3,21 @@
 import os
 import site
 
-site.addsitedir(os.path.join(os.path.dirname(os.path.dirname(__file__)), 'utils'))
+site.addsitedir(os.path.join(os.path.dirname(os.path.dirname(__file__)), "utils"))
 from libcxx.test.googlebenchmark import GoogleBenchmark
 
 # Tell pylint that we know config and lit_config exist somewhere.
-if 'PYLINT_IMPORT' in os.environ:
+if "PYLINT_IMPORT" in os.environ:
     config = object()
     lit_config = object()
 
 # name: The name of this test suite.
-config.name = 'libc++ benchmarks'
+config.name = "libc++ benchmarks"
 config.suffixes = []
 
-config.test_exec_root = os.path.join(config.libcxx_obj_root, 'benchmarks')
+config.test_exec_root = os.path.join(config.libcxx_obj_root, "benchmarks")
 config.test_source_root = config.test_exec_root
 
-config.test_format = GoogleBenchmark(test_sub_dirs='.',
-                                     test_suffix='.libcxx.out',
-                                     benchmark_args=config.benchmark_args)
\ No newline at end of file
+config.test_format = GoogleBenchmark(
+    test_sub_dirs=".", test_suffix=".libcxx.out", benchmark_args=config.benchmark_args
+)
diff --git a/libcxx/docs/conf.py b/libcxx/docs/conf.py
--- a/libcxx/docs/conf.py
+++ b/libcxx/docs/conf.py
@@ -16,106 +16,106 @@
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
+# sys.path.insert(0, os.path.abspath('.'))
 
 # -- General configuration -----------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
+# needs_sphinx = '1.0'
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.intersphinx', 'sphinx.ext.todo']
+extensions = ["sphinx.ext.intersphinx", "sphinx.ext.todo"]
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
+templates_path = ["_templates"]
 
 # The suffix of source filenames.
-source_suffix = '.rst'
+source_suffix = ".rst"
 
 # The encoding of source files.
-#source_encoding = 'utf-8-sig'
+# source_encoding = 'utf-8-sig'
 
 # The master toctree document.
-master_doc = 'index'
+master_doc = "index"
 
 # General information about the project.
-project = u'libc++'
-copyright = u'2011-%d, LLVM Project' % date.today().year
+project = "libc++"
+copyright = "2011-%d, LLVM Project" % date.today().year
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = '17.0'
+version = "17.0"
 # The full version, including alpha/beta/rc tags.
-release = '17.0'
+release = "17.0"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
-#language = None
+# language = None
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
-#today = ''
+# today = ''
 # Else, today_fmt is used as the format for a strftime call.
-today_fmt = '%Y-%m-%d'
+today_fmt = "%Y-%m-%d"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
-exclude_patterns = ['_build', 'Helpers']
+exclude_patterns = ["_build", "Helpers"]
 
 # The reST default role (used for this markup: `text`) to use for all documents.
-#default_role = None
+# default_role = None
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
+# add_function_parentheses = True
 
 # If true, the current module name will be prepended to all description
 # unit titles (such as .. function::).
-#add_module_names = True
+# add_module_names = True
 
 # If true, sectionauthor and moduleauthor directives will be shown in the
 # output. They are ignored by default.
 show_authors = True
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'friendly'
+pygments_style = "friendly"
 
 # A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
+# modindex_common_prefix = []
 
 
 # -- Options for HTML output ---------------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'haiku'
+html_theme = "haiku"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-#html_theme_options = {}
+# html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
-#html_theme_path = []
+# html_theme_path = []
 
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
-#html_title = None
+# html_title = None
 
 # A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
+# html_short_title = None
 
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-#html_logo = None
+# html_logo = None
 
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
-#html_favicon = None
+# html_favicon = None
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
@@ -124,101 +124,95 @@
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
+# html_last_updated_fmt = '%b %d, %Y'
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
-#html_use_smartypants = True
+# html_use_smartypants = True
 
 # Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
+# html_sidebars = {}
 
 # Additional templates that should be rendered to pages, maps page names to
 # template names.
-#html_additional_pages = {}
+# html_additional_pages = {}
 
 # If false, no module index is generated.
-#html_domain_indices = True
+# html_domain_indices = True
 
 # If false, no index is generated.
-#html_use_index = True
+# html_use_index = True
 
 # If true, the index is split into individual pages for each letter.
-#html_split_index = False
+# html_split_index = False
 
 # If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
+# html_show_sourcelink = True
 
 # If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
+# html_show_sphinx = True
 
 # If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
+# html_show_copyright = True
 
 # If true, an OpenSearch description file will be output, and all pages will
 # contain a <link> tag referring to it.  The value of this option must be the
 # base URL from which the finished HTML is served.
-#html_use_opensearch = ''
+# html_use_opensearch = ''
 
 # This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
+# html_file_suffix = None
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = 'libcxxdoc'
+htmlhelp_basename = "libcxxdoc"
 
 
 # -- Options for LaTeX output --------------------------------------------------
 
 latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
+    # The paper size ('letterpaper' or 'a4paper').
+    #'papersize': 'letterpaper',
+    # The font size ('10pt', '11pt' or '12pt').
+    #'pointsize': '10pt',
+    # Additional stuff for the LaTeX preamble.
+    #'preamble': '',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto/manual]).
 latex_documents = [
-  ('contents', 'libcxx.tex', u'libcxx Documentation',
-   u'LLVM project', 'manual'),
+    ("contents", "libcxx.tex", "libcxx Documentation", "LLVM project", "manual"),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
-#latex_logo = None
+# latex_logo = None
 
 # For "manual" documents, if this is true, then toplevel headings are parts,
 # not chapters.
-#latex_use_parts = False
+# latex_use_parts = False
 
 # If true, show page references after internal links.
-#latex_show_pagerefs = False
+# latex_show_pagerefs = False
 
 # If true, show URL addresses after external links.
-#latex_show_urls = False
+# latex_show_urls = False
 
 # Documents to append as an appendix to all manuals.
-#latex_appendices = []
+# latex_appendices = []
 
 # If false, no module index is generated.
-#latex_domain_indices = True
+# latex_domain_indices = True
 
 
 # -- Options for manual page output --------------------------------------------
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [
-    ('contents', 'libc++', u'libc++ Documentation',
-     [u'LLVM project'], 1)
-]
+man_pages = [("contents", "libc++", "libc++ Documentation", ["LLVM project"], 1)]
 
 # If true, show URL addresses after external links.
-#man_show_urls = False
+# man_show_urls = False
 
 
 # -- Options for Texinfo output ------------------------------------------------
@@ -227,19 +221,25 @@
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
-  ('contents', 'libc++', u'libc++ Documentation',
-   u'LLVM project', 'libc++', 'One line description of project.',
-   'Miscellaneous'),
+    (
+        "contents",
+        "libc++",
+        "libc++ Documentation",
+        "LLVM project",
+        "libc++",
+        "One line description of project.",
+        "Miscellaneous",
+    ),
 ]
 
 # Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
+# texinfo_appendices = []
 
 # If false, no module index is generated.
-#texinfo_domain_indices = True
+# texinfo_domain_indices = True
 
 # How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
+# texinfo_show_urls = 'footnote'
 
 
 # FIXME: Define intersphinx configuration.
diff --git a/libcxx/test/libcxx/experimental/lit.local.cfg b/libcxx/test/libcxx/experimental/lit.local.cfg
--- a/libcxx/test/libcxx/experimental/lit.local.cfg
+++ b/libcxx/test/libcxx/experimental/lit.local.cfg
@@ -1,3 +1,3 @@
 # Disable all of the experimental tests if the correct feature is not available.
-if 'c++experimental' not in config.available_features:
-  config.unsupported = True
+if "c++experimental" not in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py
--- a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py
+++ b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """Commands used to automate testing gdb pretty printers.
 
 This script is part of a larger framework to test gdb pretty printers. It
@@ -31,10 +31,8 @@
 
 
 class CheckResult(gdb.Command):
-
     def __init__(self):
-        super(CheckResult, self).__init__(
-            "print_and_compare", gdb.COMMAND_DATA)
+        super(CheckResult, self).__init__("print_and_compare", gdb.COMMAND_DATA)
 
     def invoke(self, arg, from_tty):
         global has_run_tests
@@ -55,7 +53,7 @@
             value_str = self._get_value_string(compare_frame, testcase_frame)
 
             # Ignore the convenience variable name and newline
-            value = value_str[value_str.find("= ") + 2:-1]
+            value = value_str[value_str.find("= ") + 2 : -1]
             gdb.newest_frame().select()
             expectation_val = compare_frame.read_var("expectation")
             check_literal = expectation_val.string(encoding="utf-8")
@@ -66,16 +64,14 @@
 
             if test_fails:
                 global test_failures
-                print("FAIL: " + test_loc.symtab.filename +
-                      ":" + str(test_loc.line))
+                print("FAIL: " + test_loc.symtab.filename + ":" + str(test_loc.line))
                 print("GDB printed:")
                 print("   " + repr(value))
                 print("Value should match:")
                 print("   " + repr(check_literal))
                 test_failures += 1
             else:
-                print("PASS: " + test_loc.symtab.filename +
-                      ":" + str(test_loc.line))
+                print("PASS: " + test_loc.symtab.filename + ":" + str(test_loc.line))
 
         except RuntimeError as e:
             # At this point, lots of different things could be wrong, so don't try to
diff --git a/libcxx/test/libcxx/input.output/file.streams/lit.local.cfg b/libcxx/test/libcxx/input.output/file.streams/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/file.streams/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/file.streams/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/input.output/filesystems/lit.local.cfg b/libcxx/test/libcxx/input.output/filesystems/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/filesystems/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/filesystems/lit.local.cfg
@@ -1,4 +1,7 @@
 # Load the same local configuration as the filesystem tests in libcxx/test/std
 import os
-std_filesystem_tests = os.path.join(config.test_source_root, 'std', 'input.output', 'filesystems')
-config.load_from_path(os.path.join(std_filesystem_tests, 'lit.local.cfg'), lit_config)
+
+std_filesystem_tests = os.path.join(
+    config.test_source_root, "std", "input.output", "filesystems"
+)
+config.load_from_path(os.path.join(std_filesystem_tests, "lit.local.cfg"), lit_config)
diff --git a/libcxx/test/libcxx/input.output/iostream.format/lit.local.cfg b/libcxx/test/libcxx/input.output/iostream.format/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/iostream.format/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/iostream.format/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/input.output/iostream.objects/lit.local.cfg b/libcxx/test/libcxx/input.output/iostream.objects/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/iostream.objects/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/iostream.objects/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/input.output/iostreams.base/lit.local.cfg b/libcxx/test/libcxx/input.output/iostreams.base/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/iostreams.base/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/iostreams.base/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/input.output/stream.buffers/lit.local.cfg b/libcxx/test/libcxx/input.output/stream.buffers/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/stream.buffers/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/stream.buffers/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/input.output/string.streams/lit.local.cfg b/libcxx/test/libcxx/input.output/string.streams/lit.local.cfg
--- a/libcxx/test/libcxx/input.output/string.streams/lit.local.cfg
+++ b/libcxx/test/libcxx/input.output/string.streams/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/lint/lint_cmakelists.sh.py b/libcxx/test/libcxx/lint/lint_cmakelists.sh.py
--- a/libcxx/test/libcxx/lint/lint_cmakelists.sh.py
+++ b/libcxx/test/libcxx/lint/lint_cmakelists.sh.py
@@ -6,25 +6,25 @@
 import os
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     libcxx_test_libcxx_lint = os.path.dirname(os.path.abspath(__file__))
-    libcxx = os.path.abspath(os.path.join(libcxx_test_libcxx_lint, '../../..'))
-    cmakelists_name = os.path.join(libcxx, 'include/CMakeLists.txt')
+    libcxx = os.path.abspath(os.path.join(libcxx_test_libcxx_lint, "../../.."))
+    cmakelists_name = os.path.join(libcxx, "include/CMakeLists.txt")
     assert os.path.isfile(cmakelists_name)
 
-    with open(cmakelists_name, 'r') as f:
+    with open(cmakelists_name, "r") as f:
         lines = f.readlines()
 
-    assert lines[0] == 'set(files\n'
+    assert lines[0] == "set(files\n"
 
     okay = True
     prevline = lines[1]
     for line in lines[2:]:
-        if (line == '  )\n'):
+        if line == "  )\n":
             break
-        if (line < prevline):
+        if line < prevline:
             okay = False
-            print('LINES OUT OF ORDER in libcxx/include/CMakeLists.txt!')
+            print("LINES OUT OF ORDER in libcxx/include/CMakeLists.txt!")
             print(prevline)
             print(line)
         prevline = line
diff --git a/libcxx/test/libcxx/lint/lint_headers.sh.py b/libcxx/test/libcxx/lint/lint_headers.sh.py
--- a/libcxx/test/libcxx/lint/lint_headers.sh.py
+++ b/libcxx/test/libcxx/lint/lint_headers.sh.py
@@ -10,45 +10,52 @@
 
 def exclude_from_consideration(path):
     return (
-        path.endswith('.txt') or
-        path.endswith('.modulemap.in') or
-        os.path.basename(path) == '__config' or
-        os.path.basename(path) == '__config_site.in' or
-        os.path.basename(path) == 'libcxx.imp' or
-        os.path.basename(path).startswith('__pstl') or # TODO: Remove once PSTL integration is finished
-        not os.path.isfile(path)
+        path.endswith(".txt")
+        or path.endswith(".modulemap.in")
+        or os.path.basename(path) == "__config"
+        or os.path.basename(path) == "__config_site.in"
+        or os.path.basename(path) == "libcxx.imp"
+        or os.path.basename(path).startswith("__pstl")
+        or not os.path.isfile(path)  # TODO: Remove once PSTL integration is finished
     )
 
 
 def check_for_pragma_GCC_system_header(pretty_fname, lines):
-    if pretty_fname not in ['__undef_macros']:
+    if pretty_fname not in ["__undef_macros"]:
         for line in lines:
-            if re.match('# *pragma GCC system_header\n', line):
+            if re.match("# *pragma GCC system_header\n", line):
                 return True
-        print('FAILED TO FIND #  pragma GCC system_header in libcxx/include/%s' % pretty_fname)
+        print(
+            "FAILED TO FIND #  pragma GCC system_header in libcxx/include/%s"
+            % pretty_fname
+        )
         return False
     return True
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     libcxx_test_libcxx_lint = os.path.dirname(os.path.abspath(__file__))
-    libcxx_include = os.path.abspath(os.path.join(libcxx_test_libcxx_lint, '../../../include'))
+    libcxx_include = os.path.abspath(
+        os.path.join(libcxx_test_libcxx_lint, "../../../include")
+    )
     assert os.path.isdir(libcxx_include)
 
     def pretty(path):
-        return path[len(libcxx_include) + 1:]
+        return path[len(libcxx_include) + 1 :]
 
     all_headers = [
-        p for p in (
-            glob.glob(os.path.join(libcxx_include, '*')) +
-            glob.glob(os.path.join(libcxx_include, '__*/*.h'))
-        ) if not exclude_from_consideration(p)
+        p
+        for p in (
+            glob.glob(os.path.join(libcxx_include, "*"))
+            + glob.glob(os.path.join(libcxx_include, "__*/*.h"))
+        )
+        if not exclude_from_consideration(p)
     ]
 
     okay = True
     for fname in all_headers:
         pretty_fname = pretty(fname)
-        with open(fname, 'r') as f:
+        with open(fname, "r") as f:
             lines = f.readlines()
 
         okay = check_for_pragma_GCC_system_header(pretty_fname, lines) and okay
diff --git a/libcxx/test/libcxx/lint/lint_modulemap.sh.py b/libcxx/test/libcxx/lint/lint_modulemap.sh.py
--- a/libcxx/test/libcxx/lint/lint_modulemap.sh.py
+++ b/libcxx/test/libcxx/lint/lint_modulemap.sh.py
@@ -7,39 +7,53 @@
 import re
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     libcxx_test_libcxx_lint = os.path.dirname(os.path.abspath(__file__))
-    libcxx = os.path.abspath(os.path.join(libcxx_test_libcxx_lint, '../../..'))
-    modulemap_name = os.path.join(libcxx, 'include/module.modulemap.in')
+    libcxx = os.path.abspath(os.path.join(libcxx_test_libcxx_lint, "../../.."))
+    modulemap_name = os.path.join(libcxx, "include/module.modulemap.in")
     assert os.path.isfile(modulemap_name)
 
     okay = True
     prevline = None
-    with open(modulemap_name, 'r') as f:
+    with open(modulemap_name, "r") as f:
         for line in f.readlines():
-            if re.match(r'^\s*module.*[{]\s*private', line):
+            if re.match(r"^\s*module.*[{]\s*private", line):
                 # Check that these lines are all of the expected format.
                 # This incidentally checks for typos in the module name.
-                if re.match(r'^\s*module (\w+)\s+[{] private header "\1(.h)?"\s+export [*] [}]', line):
+                if re.match(
+                    r'^\s*module (\w+)\s+[{] private header "\1(.h)?"\s+export [*] [}]',
+                    line,
+                ):
                     # It's a top-level private header, such as <__bit_reference>.
                     pass
-                elif re.match(r'^\s*module (\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]', line):
+                elif re.match(
+                    r'^\s*module (\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]',
+                    line,
+                ):
                     # It's a private submodule, such as <__utility/swap.h>.
                     pass
-                elif re.match(r'^\s*module (\w+)_fwd\s+[{] private header "__fwd/\1[.]h" [}]', line):
+                elif re.match(
+                    r'^\s*module (\w+)_fwd\s+[{] private header "__fwd/\1[.]h" [}]',
+                    line,
+                ):
                     # It's a private submodule with forward declarations, such as <__fwd/span.h>.
                     pass
-                elif re.match(r'^\s*module (?:\w+_)*(\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]', line):
+                elif re.match(
+                    r'^\s*module (?:\w+_)*(\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]',
+                    line,
+                ):
                     # It's a private pstl submodule, such as <__algorithm/pstl_backends/cpu_backend.h>
                     pass
                 else:
                     okay = False
-                    print("LINE DOESN'T MATCH REGEX in libcxx/include/module.modulemap.in!")
+                    print(
+                        "LINE DOESN'T MATCH REGEX in libcxx/include/module.modulemap.in!"
+                    )
                     print(line)
                 # Check that these lines are alphabetized.
                 if (prevline is not None) and (line < prevline):
                     okay = False
-                    print('LINES OUT OF ORDER in libcxx/include/module.modulemap.in!')
+                    print("LINES OUT OF ORDER in libcxx/include/module.modulemap.in!")
                     print(prevline)
                     print(line)
                 prevline = line
diff --git a/libcxx/test/libcxx/lit.local.cfg b/libcxx/test/libcxx/lit.local.cfg
--- a/libcxx/test/libcxx/lit.local.cfg
+++ b/libcxx/test/libcxx/lit.local.cfg
@@ -1,3 +1,4 @@
 # The tests in this directory need to run Python
 import pipes, sys
-config.substitutions.append(('%{python}', pipes.quote(sys.executable)))
+
+config.substitutions.append(("%{python}", pipes.quote(sys.executable)))
diff --git a/libcxx/test/libcxx/localization/lit.local.cfg b/libcxx/test/libcxx/localization/lit.local.cfg
--- a/libcxx/test/libcxx/localization/lit.local.cfg
+++ b/libcxx/test/libcxx/localization/lit.local.cfg
@@ -1,6 +1,7 @@
 # Load the same local configuration as the corresponding one in libcxx/test/std
 import os
-inLibcxx = os.path.join('libcxx', 'test', 'libcxx')
-inStd = os.path.join('libcxx', 'test', 'std')
+
+inLibcxx = os.path.join("libcxx", "test", "libcxx")
+inStd = os.path.join("libcxx", "test", "std")
 localConfig = os.path.normpath(os.path.realpath(__file__)).replace(inLibcxx, inStd)
 config.load_from_path(localConfig, lit_config)
diff --git a/libcxx/test/libcxx/selftest/additional_compile_flags/lit.local.cfg b/libcxx/test/libcxx/selftest/additional_compile_flags/lit.local.cfg
--- a/libcxx/test/libcxx/selftest/additional_compile_flags/lit.local.cfg
+++ b/libcxx/test/libcxx/selftest/additional_compile_flags/lit.local.cfg
@@ -1,2 +1,2 @@
 # Add a Lit feature so we can test conditional addition of compile flags.
-config.available_features.add('some-defined-feature')
+config.available_features.add("some-defined-feature")
diff --git a/libcxx/test/libcxx/selftest/dsl/dsl.sh.py b/libcxx/test/libcxx/selftest/dsl/dsl.sh.py
--- a/libcxx/test/libcxx/selftest/dsl/dsl.sh.py
+++ b/libcxx/test/libcxx/selftest/dsl/dsl.sh.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 # Note: We prepend arguments with 'x' to avoid thinking there are too few
 #       arguments in case an argument is an empty string.
@@ -23,15 +23,17 @@
 # Allow importing 'lit' and the 'libcxx' module. Make sure we put the lit
 # path first so we don't find any system-installed version.
 monorepoRoot = dirname(dirname(dirname(dirname(dirname(dirname(__file__))))))
-sys.path = [os.path.join(monorepoRoot, 'libcxx', 'utils'),
-            os.path.join(monorepoRoot, 'llvm', 'utils', 'lit')] + sys.path
+sys.path = [
+    os.path.join(monorepoRoot, "libcxx", "utils"),
+    os.path.join(monorepoRoot, "llvm", "utils", "lit"),
+] + sys.path
 import libcxx.test.dsl as dsl
 import lit.LitConfig
 import lit.util
 
 # Steal some parameters from the config running this test so that we can
 # bootstrap our own TestingConfig.
-args = list(map(lambda s: s[1:], sys.argv[1:8])) # Remove the leading 'x'
+args = list(map(lambda s: s[1:], sys.argv[1:8]))  # Remove the leading 'x'
 SOURCE_ROOT, EXEC_PATH, SUBSTITUTIONS = args
 sys.argv[1:8] = []
 
@@ -40,10 +42,12 @@
 for s, sub in SUBSTITUTIONS:
     print("Substitution '{}' is '{}'".format(s, sub))
 
+
 class SetupConfigs(unittest.TestCase):
     """
     Base class for the tests below -- it creates a fake TestingConfig.
     """
+
     def setUp(self):
         """
         Create a fake TestingConfig that can be populated however we wish for
@@ -51,7 +55,7 @@
         minimum required substitutions.
         """
         self.litConfig = lit.LitConfig.LitConfig(
-            progname='lit',
+            progname="lit",
             path=[],
             quiet=False,
             useValgrind=False,
@@ -59,9 +63,10 @@
             valgrindArgs=[],
             noExecute=False,
             debug=False,
-            isWindows=platform.system() == 'Windows',
-            order='smart',
-            params={})
+            isWindows=platform.system() == "Windows",
+            order="smart",
+            params={},
+        )
 
         self.config = lit.TestingConfig.TestingConfig.fromdefaults(self.litConfig)
         self.config.environment = dict(os.environ)
@@ -82,7 +87,7 @@
 
 def findIndex(list, pred):
     """Finds the index of the first element satisfying 'pred' in a list, or
-       'len(list)' if there is no such element."""
+    'len(list)' if there is no such element."""
     index = 0
     for x in list:
         if pred(x):
@@ -96,23 +101,27 @@
     """
     Tests for libcxx.test.dsl.hasCompileFlag
     """
+
     def test_no_flag_should_work(self):
-        self.assertTrue(dsl.hasCompileFlag(self.config, ''))
+        self.assertTrue(dsl.hasCompileFlag(self.config, ""))
 
     def test_flag_exists(self):
-        self.assertTrue(dsl.hasCompileFlag(self.config, '-O1'))
+        self.assertTrue(dsl.hasCompileFlag(self.config, "-O1"))
 
     def test_nonexistent_flag(self):
-        self.assertFalse(dsl.hasCompileFlag(self.config, '-this_is_not_a_flag_any_compiler_has'))
+        self.assertFalse(
+            dsl.hasCompileFlag(self.config, "-this_is_not_a_flag_any_compiler_has")
+        )
 
     def test_multiple_flags(self):
-        self.assertTrue(dsl.hasCompileFlag(self.config, '-O1 -Dhello'))
+        self.assertTrue(dsl.hasCompileFlag(self.config, "-O1 -Dhello"))
 
 
 class TestSourceBuilds(SetupConfigs):
     """
     Tests for libcxx.test.dsl.sourceBuilds
     """
+
     def test_valid_program_builds(self):
         source = """int main(int, char**) { return 0; }"""
         self.assertTrue(dsl.sourceBuilds(self.config, source))
@@ -131,6 +140,7 @@
     """
     Tests for libcxx.test.dsl.programOutput
     """
+
     def test_valid_program_returns_output(self):
         source = """
         #include <cstdio>
@@ -156,14 +166,20 @@
         source = """
         int main(int, char**) { return 1; }
         """
-        self.assertRaises(dsl.ConfigurationRuntimeError, lambda: dsl.programOutput(self.config, source))
+        self.assertRaises(
+            dsl.ConfigurationRuntimeError,
+            lambda: dsl.programOutput(self.config, source),
+        )
 
     def test_program_that_fails_to_compile_raises_compilation_error(self):
         # The program doesn't compile
         source = """
         int main(int, char**) { this doesnt compile }
         """
-        self.assertRaises(dsl.ConfigurationCompilationError, lambda: dsl.programOutput(self.config, source))
+        self.assertRaises(
+            dsl.ConfigurationCompilationError,
+            lambda: dsl.programOutput(self.config, source),
+        )
 
     def test_pass_arguments_to_program(self):
         source = """
@@ -191,14 +207,22 @@
             return 0;
         }
         """
-        compileFlagsIndex = findIndex(self.config.substitutions, lambda x: x[0] == '%{compile_flags}')
+        compileFlagsIndex = findIndex(
+            self.config.substitutions, lambda x: x[0] == "%{compile_flags}"
+        )
         compileFlags = self.config.substitutions[compileFlagsIndex][1]
 
-        self.config.substitutions[compileFlagsIndex] = ('%{compile_flags}',  compileFlags + ' -DMACRO=1')
+        self.config.substitutions[compileFlagsIndex] = (
+            "%{compile_flags}",
+            compileFlags + " -DMACRO=1",
+        )
         output1 = dsl.programOutput(self.config, source)
         self.assertEqual(output1, "MACRO=1\n")
 
-        self.config.substitutions[compileFlagsIndex] = ('%{compile_flags}',  compileFlags + ' -DMACRO=2')
+        self.config.substitutions[compileFlagsIndex] = (
+            "%{compile_flags}",
+            compileFlags + " -DMACRO=2",
+        )
         output2 = dsl.programOutput(self.config, source)
         self.assertEqual(output2, "MACRO=2\n")
 
@@ -220,6 +244,7 @@
     """
     Tests for libcxx.test.dsl.programSucceeds
     """
+
     def test_success(self):
         source = """
         int main(int, char**) { return 0; }
@@ -236,33 +261,47 @@
         source = """
         this does not compile
         """
-        self.assertRaises(dsl.ConfigurationCompilationError, lambda: dsl.programSucceeds(self.config, source))
+        self.assertRaises(
+            dsl.ConfigurationCompilationError,
+            lambda: dsl.programSucceeds(self.config, source),
+        )
+
 
 class TestHasLocale(SetupConfigs):
     """
     Tests for libcxx.test.dsl.hasLocale
     """
+
     def test_doesnt_explode(self):
         # It's really hard to test that a system has a given locale, so at least
         # make sure we don't explode when we try to check it.
         try:
-            dsl.hasAnyLocale(self.config, ['en_US.UTF-8'])
+            dsl.hasAnyLocale(self.config, ["en_US.UTF-8"])
         except subprocess.CalledProcessError:
             self.fail("checking for hasLocale should not explode")
 
     def test_nonexistent_locale(self):
-        self.assertFalse(dsl.hasAnyLocale(self.config, ['forsurethisisnotanexistinglocale']))
+        self.assertFalse(
+            dsl.hasAnyLocale(self.config, ["forsurethisisnotanexistinglocale"])
+        )
 
     def test_localization_program_doesnt_compile(self):
-        compilerIndex = findIndex(self.config.substitutions, lambda x: x[0] == '%{cxx}')
-        self.config.substitutions[compilerIndex] = ('%{cxx}', 'this-is-certainly-not-a-valid-compiler!!')
-        self.assertRaises(dsl.ConfigurationCompilationError, lambda: dsl.hasAnyLocale(self.config, ['en_US.UTF-8']))
+        compilerIndex = findIndex(self.config.substitutions, lambda x: x[0] == "%{cxx}")
+        self.config.substitutions[compilerIndex] = (
+            "%{cxx}",
+            "this-is-certainly-not-a-valid-compiler!!",
+        )
+        self.assertRaises(
+            dsl.ConfigurationCompilationError,
+            lambda: dsl.hasAnyLocale(self.config, ["en_US.UTF-8"]),
+        )
 
 
 class TestCompilerMacros(SetupConfigs):
     """
     Tests for libcxx.test.dsl.compilerMacros
     """
+
     def test_basic(self):
         macros = dsl.compilerMacros(self.config)
         self.assertIsInstance(macros, dict)
@@ -273,28 +312,29 @@
 
     def test_no_flag(self):
         macros = dsl.compilerMacros(self.config)
-        self.assertIn('__cplusplus', macros.keys())
+        self.assertIn("__cplusplus", macros.keys())
 
     def test_empty_flag(self):
-        macros = dsl.compilerMacros(self.config, '')
-        self.assertIn('__cplusplus', macros.keys())
+        macros = dsl.compilerMacros(self.config, "")
+        self.assertIn("__cplusplus", macros.keys())
 
     def test_with_flag(self):
-        macros = dsl.compilerMacros(self.config, '-DFOO=3')
-        self.assertIn('__cplusplus', macros.keys())
-        self.assertEqual(macros['FOO'], '3')
+        macros = dsl.compilerMacros(self.config, "-DFOO=3")
+        self.assertIn("__cplusplus", macros.keys())
+        self.assertEqual(macros["FOO"], "3")
 
     def test_with_flags(self):
-        macros = dsl.compilerMacros(self.config, '-DFOO=3 -DBAR=hello')
-        self.assertIn('__cplusplus', macros.keys())
-        self.assertEqual(macros['FOO'], '3')
-        self.assertEqual(macros['BAR'], 'hello')
+        macros = dsl.compilerMacros(self.config, "-DFOO=3 -DBAR=hello")
+        self.assertIn("__cplusplus", macros.keys())
+        self.assertEqual(macros["FOO"], "3")
+        self.assertEqual(macros["BAR"], "hello")
 
 
 class TestFeatureTestMacros(SetupConfigs):
     """
     Tests for libcxx.test.dsl.featureTestMacros
     """
+
     def test_basic(self):
         macros = dsl.featureTestMacros(self.config)
         self.assertIsInstance(macros, dict)
@@ -308,21 +348,22 @@
     """
     Tests for libcxx.test.dsl.Feature
     """
+
     def test_trivial(self):
-        feature = dsl.Feature(name='name')
+        feature = dsl.Feature(name="name")
         origSubstitutions = copy.deepcopy(self.config.substitutions)
         actions = feature.getActions(self.config)
         self.assertTrue(len(actions) == 1)
         for a in actions:
             a.applyTo(self.config)
         self.assertEqual(origSubstitutions, self.config.substitutions)
-        self.assertIn('name', self.config.available_features)
+        self.assertIn("name", self.config.available_features)
 
     def test_name_can_be_a_callable(self):
-        feature = dsl.Feature(name=lambda cfg: 'name')
+        feature = dsl.Feature(name=lambda cfg: "name")
         for a in feature.getActions(self.config):
             a.applyTo(self.config)
-        self.assertIn('name', self.config.available_features)
+        self.assertIn("name", self.config.available_features)
 
     def test_name_is_not_a_string_1(self):
         feature = dsl.Feature(name=None)
@@ -335,159 +376,250 @@
         self.assertRaises(ValueError, lambda: feature.pretty(self.config))
 
     def test_adding_action(self):
-        feature = dsl.Feature(name='name', actions=[dsl.AddCompileFlag('-std=c++03')])
-        origLinkFlags = copy.deepcopy(self.getSubstitution('%{link_flags}'))
+        feature = dsl.Feature(name="name", actions=[dsl.AddCompileFlag("-std=c++03")])
+        origLinkFlags = copy.deepcopy(self.getSubstitution("%{link_flags}"))
         for a in feature.getActions(self.config):
             a.applyTo(self.config)
-        self.assertIn('name', self.config.available_features)
-        self.assertIn('-std=c++03', self.getSubstitution('%{compile_flags}'))
-        self.assertEqual(origLinkFlags, self.getSubstitution('%{link_flags}'))
+        self.assertIn("name", self.config.available_features)
+        self.assertIn("-std=c++03", self.getSubstitution("%{compile_flags}"))
+        self.assertEqual(origLinkFlags, self.getSubstitution("%{link_flags}"))
 
     def test_actions_can_be_a_callable(self):
-        feature = dsl.Feature(name='name',
-                              actions=lambda cfg: (
-                                self.assertIs(self.config, cfg),
-                                [dsl.AddCompileFlag('-std=c++03')]
-                              )[1])
+        feature = dsl.Feature(
+            name="name",
+            actions=lambda cfg: (
+                self.assertIs(self.config, cfg),
+                [dsl.AddCompileFlag("-std=c++03")],
+            )[1],
+        )
         for a in feature.getActions(self.config):
             a.applyTo(self.config)
-        self.assertIn('-std=c++03', self.getSubstitution('%{compile_flags}'))
+        self.assertIn("-std=c++03", self.getSubstitution("%{compile_flags}"))
 
     def test_unsupported_feature(self):
-        feature = dsl.Feature(name='name', when=lambda _: False)
+        feature = dsl.Feature(name="name", when=lambda _: False)
         self.assertEqual(feature.getActions(self.config), [])
 
     def test_is_supported_gets_passed_the_config(self):
-        feature = dsl.Feature(name='name', when=lambda cfg: (self.assertIs(self.config, cfg), True)[1])
+        feature = dsl.Feature(
+            name="name", when=lambda cfg: (self.assertIs(self.config, cfg), True)[1]
+        )
         self.assertEqual(len(feature.getActions(self.config)), 1)
 
 
 def _throw():
     raise ValueError()
 
+
 class TestParameter(SetupConfigs):
     """
     Tests for libcxx.test.dsl.Parameter
     """
+
     def test_empty_name_should_blow_up(self):
-        self.assertRaises(ValueError, lambda: dsl.Parameter(name='', choices=['c++03'], type=str, help='', actions=lambda _: []))
+        self.assertRaises(
+            ValueError,
+            lambda: dsl.Parameter(
+                name="", choices=["c++03"], type=str, help="", actions=lambda _: []
+            ),
+        )
 
     def test_empty_choices_should_blow_up(self):
-        self.assertRaises(ValueError, lambda: dsl.Parameter(name='std', choices=[], type=str, help='', actions=lambda _: []))
+        self.assertRaises(
+            ValueError,
+            lambda: dsl.Parameter(
+                name="std", choices=[], type=str, help="", actions=lambda _: []
+            ),
+        )
 
     def test_no_choices_is_ok(self):
-        param = dsl.Parameter(name='triple', type=str, help='', actions=lambda _: [])
-        self.assertEqual(param.name, 'triple')
+        param = dsl.Parameter(name="triple", type=str, help="", actions=lambda _: [])
+        self.assertEqual(param.name, "triple")
 
     def test_name_is_set_correctly(self):
-        param = dsl.Parameter(name='std', choices=['c++03'], type=str, help='', actions=lambda _: [])
-        self.assertEqual(param.name, 'std')
+        param = dsl.Parameter(
+            name="std", choices=["c++03"], type=str, help="", actions=lambda _: []
+        )
+        self.assertEqual(param.name, "std")
 
     def test_no_value_provided_and_no_default_value(self):
-        param = dsl.Parameter(name='std', choices=['c++03'], type=str, help='', actions=lambda _: [])
-        self.assertRaises(ValueError, lambda: param.getActions(self.config, self.litConfig.params))
+        param = dsl.Parameter(
+            name="std", choices=["c++03"], type=str, help="", actions=lambda _: []
+        )
+        self.assertRaises(
+            ValueError, lambda: param.getActions(self.config, self.litConfig.params)
+        )
 
     def test_no_value_provided_and_default_value(self):
-        param = dsl.Parameter(name='std', choices=['c++03'], type=str, help='', default='c++03',
-                              actions=lambda std: [dsl.AddFeature(std)])
+        param = dsl.Parameter(
+            name="std",
+            choices=["c++03"],
+            type=str,
+            help="",
+            default="c++03",
+            actions=lambda std: [dsl.AddFeature(std)],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('c++03', self.config.available_features)
+        self.assertIn("c++03", self.config.available_features)
 
     def test_value_provided_on_command_line_and_no_default_value(self):
-        self.litConfig.params['std'] = 'c++03'
-        param = dsl.Parameter(name='std', choices=['c++03'], type=str, help='',
-                              actions=lambda std: [dsl.AddFeature(std)])
+        self.litConfig.params["std"] = "c++03"
+        param = dsl.Parameter(
+            name="std",
+            choices=["c++03"],
+            type=str,
+            help="",
+            actions=lambda std: [dsl.AddFeature(std)],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('c++03', self.config.available_features)
+        self.assertIn("c++03", self.config.available_features)
 
     def test_value_provided_on_command_line_and_default_value(self):
         """The value provided on the command line should override the default value"""
-        self.litConfig.params['std'] = 'c++11'
-        param = dsl.Parameter(name='std', choices=['c++03', 'c++11'], type=str, default='c++03', help='',
-                              actions=lambda std: [dsl.AddFeature(std)])
+        self.litConfig.params["std"] = "c++11"
+        param = dsl.Parameter(
+            name="std",
+            choices=["c++03", "c++11"],
+            type=str,
+            default="c++03",
+            help="",
+            actions=lambda std: [dsl.AddFeature(std)],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('c++11', self.config.available_features)
-        self.assertNotIn('c++03', self.config.available_features)
+        self.assertIn("c++11", self.config.available_features)
+        self.assertNotIn("c++03", self.config.available_features)
 
     def test_value_provided_in_config_and_default_value(self):
         """The value provided in the config should override the default value"""
-        self.config.std ='c++11'
-        param = dsl.Parameter(name='std', choices=['c++03', 'c++11'], type=str, default='c++03', help='',
-                              actions=lambda std: [dsl.AddFeature(std)])
+        self.config.std = "c++11"
+        param = dsl.Parameter(
+            name="std",
+            choices=["c++03", "c++11"],
+            type=str,
+            default="c++03",
+            help="",
+            actions=lambda std: [dsl.AddFeature(std)],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('c++11', self.config.available_features)
-        self.assertNotIn('c++03', self.config.available_features)
+        self.assertIn("c++11", self.config.available_features)
+        self.assertNotIn("c++03", self.config.available_features)
 
     def test_value_provided_in_config_and_on_command_line(self):
         """The value on the command line should override the one in the config"""
-        self.config.std = 'c++11'
-        self.litConfig.params['std'] = 'c++03'
-        param = dsl.Parameter(name='std', choices=['c++03', 'c++11'], type=str, help='',
-                              actions=lambda std: [dsl.AddFeature(std)])
+        self.config.std = "c++11"
+        self.litConfig.params["std"] = "c++03"
+        param = dsl.Parameter(
+            name="std",
+            choices=["c++03", "c++11"],
+            type=str,
+            help="",
+            actions=lambda std: [dsl.AddFeature(std)],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('c++03', self.config.available_features)
-        self.assertNotIn('c++11', self.config.available_features)
+        self.assertIn("c++03", self.config.available_features)
+        self.assertNotIn("c++11", self.config.available_features)
 
     def test_no_actions(self):
-        self.litConfig.params['std'] = 'c++03'
-        param = dsl.Parameter(name='std', choices=['c++03'], type=str, help='',
-                              actions=lambda _: [])
+        self.litConfig.params["std"] = "c++03"
+        param = dsl.Parameter(
+            name="std", choices=["c++03"], type=str, help="", actions=lambda _: []
+        )
         actions = param.getActions(self.config, self.litConfig.params)
         self.assertEqual(actions, [])
 
     def test_boolean_value_parsed_from_trueish_string_parameter(self):
-        self.litConfig.params['enable_exceptions'] = "True"
-        param = dsl.Parameter(name='enable_exceptions', choices=[True, False], type=bool, help='',
-                              actions=lambda exceptions: [] if exceptions else _throw())
+        self.litConfig.params["enable_exceptions"] = "True"
+        param = dsl.Parameter(
+            name="enable_exceptions",
+            choices=[True, False],
+            type=bool,
+            help="",
+            actions=lambda exceptions: [] if exceptions else _throw(),
+        )
         self.assertEqual(param.getActions(self.config, self.litConfig.params), [])
 
     def test_boolean_value_from_true_boolean_parameter(self):
-        self.litConfig.params['enable_exceptions'] = True
-        param = dsl.Parameter(name='enable_exceptions', choices=[True, False], type=bool, help='',
-                              actions=lambda exceptions: [] if exceptions else _throw())
+        self.litConfig.params["enable_exceptions"] = True
+        param = dsl.Parameter(
+            name="enable_exceptions",
+            choices=[True, False],
+            type=bool,
+            help="",
+            actions=lambda exceptions: [] if exceptions else _throw(),
+        )
         self.assertEqual(param.getActions(self.config, self.litConfig.params), [])
 
     def test_boolean_value_parsed_from_falseish_string_parameter(self):
-        self.litConfig.params['enable_exceptions'] = "False"
-        param = dsl.Parameter(name='enable_exceptions', choices=[True, False], type=bool, help='',
-                              actions=lambda exceptions: [] if exceptions else [dsl.AddFeature("-fno-exceptions")])
+        self.litConfig.params["enable_exceptions"] = "False"
+        param = dsl.Parameter(
+            name="enable_exceptions",
+            choices=[True, False],
+            type=bool,
+            help="",
+            actions=lambda exceptions: []
+            if exceptions
+            else [dsl.AddFeature("-fno-exceptions")],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('-fno-exceptions', self.config.available_features)
+        self.assertIn("-fno-exceptions", self.config.available_features)
 
     def test_boolean_value_from_false_boolean_parameter(self):
-        self.litConfig.params['enable_exceptions'] = False
-        param = dsl.Parameter(name='enable_exceptions', choices=[True, False], type=bool, help='',
-                              actions=lambda exceptions: [] if exceptions else [dsl.AddFeature("-fno-exceptions")])
+        self.litConfig.params["enable_exceptions"] = False
+        param = dsl.Parameter(
+            name="enable_exceptions",
+            choices=[True, False],
+            type=bool,
+            help="",
+            actions=lambda exceptions: []
+            if exceptions
+            else [dsl.AddFeature("-fno-exceptions")],
+        )
         for a in param.getActions(self.config, self.litConfig.params):
             a.applyTo(self.config)
-        self.assertIn('-fno-exceptions', self.config.available_features)
+        self.assertIn("-fno-exceptions", self.config.available_features)
 
     def test_list_parsed_from_comma_delimited_string_empty(self):
-        self.litConfig.params['additional_features'] = ""
-        param = dsl.Parameter(name='additional_features', type=list, help='', actions=lambda f: f)
+        self.litConfig.params["additional_features"] = ""
+        param = dsl.Parameter(
+            name="additional_features", type=list, help="", actions=lambda f: f
+        )
         self.assertEqual(param.getActions(self.config, self.litConfig.params), [])
 
     def test_list_parsed_from_comma_delimited_string_1(self):
-        self.litConfig.params['additional_features'] = "feature1"
-        param = dsl.Parameter(name='additional_features', type=list, help='', actions=lambda f: f)
-        self.assertEqual(param.getActions(self.config, self.litConfig.params), ['feature1'])
+        self.litConfig.params["additional_features"] = "feature1"
+        param = dsl.Parameter(
+            name="additional_features", type=list, help="", actions=lambda f: f
+        )
+        self.assertEqual(
+            param.getActions(self.config, self.litConfig.params), ["feature1"]
+        )
 
     def test_list_parsed_from_comma_delimited_string_2(self):
-        self.litConfig.params['additional_features'] = "feature1,feature2"
-        param = dsl.Parameter(name='additional_features', type=list, help='', actions=lambda f: f)
-        self.assertEqual(param.getActions(self.config, self.litConfig.params), ['feature1', 'feature2'])
+        self.litConfig.params["additional_features"] = "feature1,feature2"
+        param = dsl.Parameter(
+            name="additional_features", type=list, help="", actions=lambda f: f
+        )
+        self.assertEqual(
+            param.getActions(self.config, self.litConfig.params),
+            ["feature1", "feature2"],
+        )
 
     def test_list_parsed_from_comma_delimited_string_3(self):
-        self.litConfig.params['additional_features'] = "feature1,feature2, feature3"
-        param = dsl.Parameter(name='additional_features', type=list, help='', actions=lambda f: f)
-        self.assertEqual(param.getActions(self.config, self.litConfig.params), ['feature1', 'feature2', 'feature3'])
+        self.litConfig.params["additional_features"] = "feature1,feature2, feature3"
+        param = dsl.Parameter(
+            name="additional_features", type=list, help="", actions=lambda f: f
+        )
+        self.assertEqual(
+            param.getActions(self.config, self.litConfig.params),
+            ["feature1", "feature2", "feature3"],
+        )
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     unittest.main(verbosity=2)
diff --git a/libcxx/test/libcxx/selftest/dsl/lit.local.cfg b/libcxx/test/libcxx/selftest/dsl/lit.local.cfg
--- a/libcxx/test/libcxx/selftest/dsl/lit.local.cfg
+++ b/libcxx/test/libcxx/selftest/dsl/lit.local.cfg
@@ -9,6 +9,7 @@
 # to pass it to the test, and we decode and unpickle the substitutions from
 # within the test.
 import base64, lit.util, pickle
+
 base64Encode = lambda s: lit.util.to_string(base64.b64encode(lit.util.to_bytes(s)))
 escapedSubstitutions = base64Encode(pickle.dumps(config.substitutions))
-config.substitutions.append(('%{substitutions}', escapedSubstitutions))
+config.substitutions.append(("%{substitutions}", escapedSubstitutions))
diff --git a/libcxx/test/libcxx/transitive_includes_to_csv.py b/libcxx/test/libcxx/transitive_includes_to_csv.py
--- a/libcxx/test/libcxx/transitive_includes_to_csv.py
+++ b/libcxx/test/libcxx/transitive_includes_to_csv.py
@@ -41,7 +41,8 @@
 # literal level.)
 LIBCXX_HEADER_REGEX = r".*c\+\+(?:/|\\\\)v[0-9]+(?:/|\\\\)(.+)"
 
-def is_libcxx_public_header(header : str) -> bool:
+
+def is_libcxx_public_header(header: str) -> bool:
     """
     Returns whether a header is a C++ public header file.
     """
@@ -62,7 +63,7 @@
     return True
 
 
-def is_libcxx_header(header : str) -> bool:
+def is_libcxx_header(header: str) -> bool:
     """
     Returns whether a header is a libc++ header, excluding the C-compatibility headers.
     """
@@ -73,7 +74,9 @@
 
     # Skip C compatibility headers (in particular, make sure not to skip libc++ detail headers).
     relative = match.group(1)
-    if relative.endswith(".h") and not (relative.startswith("__") or re.search(r"(/|\\\\)__", relative)):
+    if relative.endswith(".h") and not (
+        relative.startswith("__") or re.search(r"(/|\\\\)__", relative)
+    ):
         return False
 
     return True
@@ -130,7 +133,9 @@
         # Get actual filenames relative to libc++'s installation directory instead of full paths
         relative = lambda h: re.match(LIBCXX_HEADER_REGEX, h).group(1)
 
-        top_level = relative(next(h.name for h in headers if h.level == 1)) # There should be only one top-level header
+        top_level = relative(
+            next(h.name for h in headers if h.level == 1)
+        )  # There should be only one top-level header
         includes = [relative(h.name) for h in headers if h.level != 1]
 
         # Remove duplicates in all includes.
diff --git a/libcxx/test/lit.cfg.py b/libcxx/test/lit.cfg.py
--- a/libcxx/test/lit.cfg.py
+++ b/libcxx/test/lit.cfg.py
@@ -7,4 +7,5 @@
 lit_config.fatal(
     "You seem to be running Lit directly -- you should be running Lit through "
     "<build>/bin/llvm-lit, which will ensure that the right Lit configuration "
-    "file is used.")
+    "file is used."
+)
diff --git a/libcxx/test/std/depr/depr.ios.members/lit.local.cfg b/libcxx/test/std/depr/depr.ios.members/lit.local.cfg
--- a/libcxx/test/std/depr/depr.ios.members/lit.local.cfg
+++ b/libcxx/test/std/depr/depr.ios.members/lit.local.cfg
@@ -1,2 +1,2 @@
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/depr/depr.str.strstreams/lit.local.cfg b/libcxx/test/std/depr/depr.str.strstreams/lit.local.cfg
--- a/libcxx/test/std/depr/depr.str.strstreams/lit.local.cfg
+++ b/libcxx/test/std/depr/depr.str.strstreams/lit.local.cfg
@@ -1,2 +1,2 @@
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/experimental/lit.local.cfg b/libcxx/test/std/experimental/lit.local.cfg
--- a/libcxx/test/std/experimental/lit.local.cfg
+++ b/libcxx/test/std/experimental/lit.local.cfg
@@ -1,3 +1,3 @@
 # Disable all of the experimental tests if the correct feature is not available.
-if 'c++experimental' not in config.available_features:
-  config.unsupported = True
+if "c++experimental" not in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/file.streams/lit.local.cfg b/libcxx/test/std/input.output/file.streams/lit.local.cfg
--- a/libcxx/test/std/input.output/file.streams/lit.local.cfg
+++ b/libcxx/test/std/input.output/file.streams/lit.local.cfg
@@ -1,6 +1,6 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
 
-if 'no-fstream' in config.available_features:
-  config.unsupported = True
+if "no-fstream" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/filesystems/lit.local.cfg b/libcxx/test/std/input.output/filesystems/lit.local.cfg
--- a/libcxx/test/std/input.output/filesystems/lit.local.cfg
+++ b/libcxx/test/std/input.output/filesystems/lit.local.cfg
@@ -1,5 +1,5 @@
-if 'availability-filesystem-missing' in config.available_features:
-  config.unsupported = True
+if "availability-filesystem-missing" in config.available_features:
+    config.unsupported = True
 
-if 'no-filesystem' in config.available_features:
+if "no-filesystem" in config.available_features:
     config.unsupported = True
diff --git a/libcxx/test/std/input.output/input.output.general/lit.local.cfg b/libcxx/test/std/input.output/input.output.general/lit.local.cfg
--- a/libcxx/test/std/input.output/input.output.general/lit.local.cfg
+++ b/libcxx/test/std/input.output/input.output.general/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/iostream.format/lit.local.cfg b/libcxx/test/std/input.output/iostream.format/lit.local.cfg
--- a/libcxx/test/std/input.output/iostream.format/lit.local.cfg
+++ b/libcxx/test/std/input.output/iostream.format/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/iostream.forward/lit.local.cfg b/libcxx/test/std/input.output/iostream.forward/lit.local.cfg
--- a/libcxx/test/std/input.output/iostream.forward/lit.local.cfg
+++ b/libcxx/test/std/input.output/iostream.forward/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/iostream.objects/lit.local.cfg b/libcxx/test/std/input.output/iostream.objects/lit.local.cfg
--- a/libcxx/test/std/input.output/iostream.objects/lit.local.cfg
+++ b/libcxx/test/std/input.output/iostream.objects/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/iostreams.base/lit.local.cfg b/libcxx/test/std/input.output/iostreams.base/lit.local.cfg
--- a/libcxx/test/std/input.output/iostreams.base/lit.local.cfg
+++ b/libcxx/test/std/input.output/iostreams.base/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/iostreams.requirements/lit.local.cfg b/libcxx/test/std/input.output/iostreams.requirements/lit.local.cfg
--- a/libcxx/test/std/input.output/iostreams.requirements/lit.local.cfg
+++ b/libcxx/test/std/input.output/iostreams.requirements/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/stream.buffers/lit.local.cfg b/libcxx/test/std/input.output/stream.buffers/lit.local.cfg
--- a/libcxx/test/std/input.output/stream.buffers/lit.local.cfg
+++ b/libcxx/test/std/input.output/stream.buffers/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/input.output/string.streams/lit.local.cfg b/libcxx/test/std/input.output/string.streams/lit.local.cfg
--- a/libcxx/test/std/input.output/string.streams/lit.local.cfg
+++ b/libcxx/test/std/input.output/string.streams/lit.local.cfg
@@ -1,3 +1,3 @@
 # All non-trivial uses of iostreams require localization support
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/iterators/stream.iterators/lit.local.cfg b/libcxx/test/std/iterators/stream.iterators/lit.local.cfg
--- a/libcxx/test/std/iterators/stream.iterators/lit.local.cfg
+++ b/libcxx/test/std/iterators/stream.iterators/lit.local.cfg
@@ -1,3 +1,3 @@
 # stream iterators rely on the streams library, which requires localization
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/localization/lit.local.cfg b/libcxx/test/std/localization/lit.local.cfg
--- a/libcxx/test/std/localization/lit.local.cfg
+++ b/libcxx/test/std/localization/lit.local.cfg
@@ -1,3 +1,3 @@
 # <locale> tests are obviously not supported when localization support is disabled
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/re/lit.local.cfg b/libcxx/test/std/re/lit.local.cfg
--- a/libcxx/test/std/re/lit.local.cfg
+++ b/libcxx/test/std/re/lit.local.cfg
@@ -1,3 +1,3 @@
 # Unfortunately, <regex> uses locales in regex_traits
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/lit.local.cfg b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/lit.local.cfg
--- a/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/lit.local.cfg
+++ b/libcxx/test/std/strings/basic.string/string.nonmembers/string.io/lit.local.cfg
@@ -1,3 +1,3 @@
 # These std::string functions require iostreams, which requires localization
-if 'no-localization' in config.available_features:
-  config.unsupported = True
+if "no-localization" in config.available_features:
+    config.unsupported = True
diff --git a/libcxx/utils/cat_files.py b/libcxx/utils/cat_files.py
--- a/libcxx/utils/cat_files.py
+++ b/libcxx/utils/cat_files.py
@@ -1,45 +1,51 @@
 #!/usr/bin/env python
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 from argparse import ArgumentParser
 import sys
 
+
 def print_and_exit(msg):
-    sys.stderr.write(msg + '\n')
+    sys.stderr.write(msg + "\n")
     sys.exit(1)
 
+
 def main():
-    parser = ArgumentParser(
-        description="Concatenate two files into a single file")
+    parser = ArgumentParser(description="Concatenate two files into a single file")
     parser.add_argument(
-        '-o', '--output', dest='output', required=True,
-        help='The output file. stdout is used if not given',
-        type=str, action='store')
+        "-o",
+        "--output",
+        dest="output",
+        required=True,
+        help="The output file. stdout is used if not given",
+        type=str,
+        action="store",
+    )
     parser.add_argument(
-        'files', metavar='files',  nargs='+',
-        help='The files to concatenate')
+        "files", metavar="files", nargs="+", help="The files to concatenate"
+    )
 
     args = parser.parse_args()
 
     if len(args.files) < 2:
-        print_and_exit('fewer than 2 inputs provided')
-    data = ''
+        print_and_exit("fewer than 2 inputs provided")
+    data = ""
     for filename in args.files:
-        with open(filename, 'r') as f:
+        with open(filename, "r") as f:
             data += f.read()
-        if len(data) != 0 and data[-1] != '\n':
-            data += '\n'
+        if len(data) != 0 and data[-1] != "\n":
+            data += "\n"
     assert len(data) > 0 and "cannot cat empty files"
-    with open(args.output, 'w') as f:
+    with open(args.output, "w") as f:
         f.write(data)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     main()
     sys.exit(0)
diff --git a/libcxx/utils/gdb/libcxx/printers.py b/libcxx/utils/gdb/libcxx/printers.py
--- a/libcxx/utils/gdb/libcxx/printers.py
+++ b/libcxx/utils/gdb/libcxx/printers.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """GDB pretty-printers for libc++.
 
 These should work for objects compiled with either the stable ABI or the unstable ABI.
@@ -29,6 +29,7 @@
 
 _libcpp_big_endian = False
 
+
 def addr_as_long(addr):
     return int(addr.cast(_long_int_type))
 
@@ -97,10 +98,11 @@
 # Some common substitutions on the types to reduce visual clutter (A user who
 # wants to see the actual details can always use print/r).
 _common_substitutions = [
-    ("std::basic_string<char, std::char_traits<char>, std::allocator<char> >",
-     "std::string"),
-    ("std::basic_string_view<char, std::char_traits<char> >",
-     "std::string_view"),
+    (
+        "std::basic_string<char, std::char_traits<char>, std::allocator<char> >",
+        "std::string",
+    ),
+    ("std::basic_string_view<char, std::char_traits<char> >", "std::string_view"),
 ]
 
 
@@ -116,8 +118,11 @@
     """
 
     type_without_typedefs = gdb_type.strip_typedefs()
-    typename = type_without_typedefs.name or type_without_typedefs.tag or \
-        str(type_without_typedefs)
+    typename = (
+        type_without_typedefs.name
+        or type_without_typedefs.tag
+        or str(type_without_typedefs)
+    )
     result = _remove_cxx_namespace(typename)
     for find_str, subst_str in _common_substitutions:
         result = re.sub(find_str, subst_str, result)
@@ -247,18 +252,18 @@
     """Print a std::string_view."""
 
     def __init__(self, val):
-      self.val = val
+        self.val = val
 
     def display_hint(self):
-      return "string"
+        return "string"
 
     def to_string(self):  # pylint: disable=g-bad-name
-      """GDB calls this to compute the pretty-printed form."""
+        """GDB calls this to compute the pretty-printed form."""
 
-      ptr = _data_field(self.val)
-      ptr = ptr.cast(ptr.type.target().strip_typedefs().pointer())
-      size = _size_field(self.val)
-      return ptr.lazy_string(length=size)
+        ptr = _data_field(self.val)
+        ptr = ptr.cast(ptr.type.target().strip_typedefs().pointer())
+        size = _size_field(self.val)
+        return ptr.lazy_string(length=size)
 
 
 class StdUniquePtrPrinter(object):
@@ -273,9 +278,10 @@
         typename = _remove_generics(_prettify_typename(self.val.type))
         if not self.addr:
             return "%s is nullptr" % typename
-        return ("%s<%s> containing" %
-                (typename,
-                 _remove_generics(_prettify_typename(self.pointee_type))))
+        return "%s<%s> containing" % (
+            typename,
+            _remove_generics(_prettify_typename(self.pointee_type)),
+        )
 
     def __iter__(self):
         if self.addr:
@@ -296,7 +302,8 @@
         """Returns self as a string."""
         typename = _remove_generics(_prettify_typename(self.val.type))
         pointee_type = _remove_generics(
-            _prettify_typename(self.val.type.template_argument(0)))
+            _prettify_typename(self.val.type.template_argument(0))
+        )
         if not self.addr:
             return "%s is nullptr" % typename
         refcount = self.val["__cntrl_"]
@@ -391,20 +398,24 @@
             self.typename += "<bool>"
             self.length = self.val["__size_"]
             bits_per_word = self.val["__bits_per_word"]
-            self.capacity = _value_of_pair_first(
-                self.val["__cap_alloc_"]) * bits_per_word
-            self.iterator = self._VectorBoolIterator(
-                begin, self.length, bits_per_word)
+            self.capacity = (
+                _value_of_pair_first(self.val["__cap_alloc_"]) * bits_per_word
+            )
+            self.iterator = self._VectorBoolIterator(begin, self.length, bits_per_word)
         else:
             end = self.val["__end_"]
             self.length = end - begin
-            self.capacity = _get_base_subobject(
-                self.val["__end_cap_"])["__value_"] - begin
+            self.capacity = (
+                _get_base_subobject(self.val["__end_cap_"])["__value_"] - begin
+            )
             self.iterator = self._VectorIterator(begin, end)
 
     def to_string(self):
-        return ("%s of length %d, capacity %d" %
-                (self.typename, self.length, self.capacity))
+        return "%s of length %d, capacity %d" % (
+            self.typename,
+            self.length,
+            self.capacity,
+        )
 
     def children(self):
         return self.iterator
@@ -424,8 +435,9 @@
         if self.n_words == 1:
             self.values = [int(self.val["__first_"])]
         else:
-            self.values = [int(self.val["__first_"][index])
-                           for index in range(self.n_words)]
+            self.values = [
+                int(self.val["__first_"][index]) for index in range(self.n_words)
+            ]
 
     def to_string(self):
         typename = _prettify_typename(self.val.type)
@@ -454,8 +466,7 @@
         self.start_ptr = self.val["__map_"]["__begin_"]
         self.first_block_start_index = int(self.val["__start_"])
         self.node_type = self.start_ptr.type
-        self.block_size = self._calculate_block_size(
-            val.type.template_argument(0))
+        self.block_size = self._calculate_block_size(val.type.template_argument(0))
 
     def _calculate_block_size(self, element_type):
         """Calculates the number of elements in a full block."""
@@ -473,13 +484,13 @@
         current_addr = self.start_ptr
         start_index = self.first_block_start_index
         while num_emitted < self.size:
-            end_index = min(start_index + self.size -
-                            num_emitted, self.block_size)
+            end_index = min(start_index + self.size - num_emitted, self.block_size)
             for _, elem in self._bucket_it(current_addr, start_index, end_index):
                 yield "", elem
             num_emitted += end_index - start_index
-            current_addr = gdb.Value(addr_as_long(current_addr) + _pointer_size) \
-                              .cast(self.node_type)
+            current_addr = gdb.Value(addr_as_long(current_addr) + _pointer_size).cast(
+                self.node_type
+            )
             start_index = 0
 
     def to_string(self):
@@ -507,8 +518,10 @@
         self.size = int(_value_of_pair_first(size_alloc_field))
         dummy_node = self.val["__end_"]
         self.nodetype = gdb.lookup_type(
-            re.sub("__list_node_base", "__list_node",
-                   str(dummy_node.type.strip_typedefs()))).pointer()
+            re.sub(
+                "__list_node_base", "__list_node", str(dummy_node.type.strip_typedefs())
+            )
+        ).pointer()
         self.first_node = dummy_node["__next_"]
 
     def to_string(self):
@@ -685,7 +698,8 @@
 
     def _init_cast_type(self, val_type):
         map_it_type = gdb.lookup_type(
-            str(val_type.strip_typedefs()) + "::iterator").strip_typedefs()
+            str(val_type.strip_typedefs()) + "::iterator"
+        ).strip_typedefs()
         tree_it_type = map_it_type.template_argument(0)
         node_ptr_type = tree_it_type.template_argument(1)
         return node_ptr_type
@@ -703,7 +717,8 @@
 
     def _init_cast_type(self, val_type):
         set_it_type = gdb.lookup_type(
-            str(val_type.strip_typedefs()) + "::iterator").strip_typedefs()
+            str(val_type.strip_typedefs()) + "::iterator"
+        ).strip_typedefs()
         node_ptr_type = set_it_type.template_argument(1)
         return node_ptr_type
 
@@ -730,8 +745,7 @@
     def _is_valid_node(self):
         if not self.util.parent(self.addr):
             return False
-        return self.util.is_left_child(self.addr) or \
-            self.util.is_right_child(self.addr)
+        return self.util.is_left_child(self.addr) or self.util.is_right_child(self.addr)
 
     def to_string(self):
         if not self.addr:
@@ -756,8 +770,7 @@
     """Print a std::(multi)map iterator."""
 
     def __init__(self, val):
-        self._initialize(val["__i_"],
-                         _remove_generics(_prettify_typename(val.type)))
+        self._initialize(val["__i_"], _remove_generics(_prettify_typename(val.type)))
 
     def _get_node_value(self, node):
         return _cc_field(node)
@@ -976,10 +989,12 @@
         # Don't attempt types known to be inside libstdcxx.
         typename = val.type.name or val.type.tag or str(val.type)
         match = re.match("^std::(__.*?)::", typename)
-        if match is not None and match.group(1) in ["__cxx1998",
-                                                    "__debug",
-                                                    "__7",
-                                                    "__g"]:
+        if match is not None and match.group(1) in [
+            "__cxx1998",
+            "__debug",
+            "__7",
+            "__g",
+        ]:
             return None
 
         # Handle any using declarations or other typedefs.
@@ -1005,13 +1020,13 @@
     # already generated as part of a larger data structure, and there is
     # no python api to get the endianness. Mixed-endianness debugging
     # rare enough that this workaround should be adequate.
-    _libcpp_big_endian = "big endian" in gdb.execute("show endian",
-                                                     to_string=True)
+    _libcpp_big_endian = "big endian" in gdb.execute("show endian", to_string=True)
 
     if not getattr(progspace, _libcxx_printer_name, False):
         print("Loading libc++ pretty-printers.")
         gdb.printing.register_pretty_printer(
-            progspace, LibcxxPrettyPrinter(_libcxx_printer_name))
+            progspace, LibcxxPrettyPrinter(_libcxx_printer_name)
+        )
         setattr(progspace, _libcxx_printer_name, True)
 
 
diff --git a/libcxx/utils/generate_abi_list.py b/libcxx/utils/generate_abi_list.py
--- a/libcxx/utils/generate_abi_list.py
+++ b/libcxx/utils/generate_abi_list.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 import argparse
 import io
@@ -14,27 +14,38 @@
 import pprint
 import sys
 
+
 def OutputFile(file):
     if isinstance(file, io.IOBase):
         return file
     assert isinstance(file, str), "Got object {} which is not a str".format(file)
-    return open(file, 'w', newline='\n')
+    return open(file, "w", newline="\n")
+
 
 def main(argv):
     parser = argparse.ArgumentParser(
-        description='Extract a list of symbols from a shared library.')
-    parser.add_argument('library', metavar='LIB', type=str,
-        help='The library to extract symbols from.')
-    parser.add_argument('-o', '--output', dest='output', type=OutputFile, default=sys.stdout,
-        help='The output file to write the symbols to. It is overwritten if it already exists. '
-             'If no file is specified, the results are written to standard output.')
+        description="Extract a list of symbols from a shared library."
+    )
+    parser.add_argument(
+        "library", metavar="LIB", type=str, help="The library to extract symbols from."
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        dest="output",
+        type=OutputFile,
+        default=sys.stdout,
+        help="The output file to write the symbols to. It is overwritten if it already exists. "
+        "If no file is specified, the results are written to standard output.",
+    )
     args = parser.parse_args(argv)
 
     symbols = libcxx.sym_check.extract.extract_symbols(args.library)
     symbols, _ = libcxx.sym_check.util.filter_stdlib_symbols(symbols)
 
     lines = [pprint.pformat(sym, width=99999) for sym in symbols]
-    args.output.writelines('\n'.join(sorted(lines)))
+    args.output.writelines("\n".join(sorted(lines)))
+
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     main(sys.argv[1:])
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -4,30 +4,43 @@
 from builtins import range
 from functools import reduce
 
+
 def get_libcxx_paths():
-  utils_path = os.path.dirname(os.path.abspath(__file__))
-  script_name = os.path.basename(__file__)
-  assert os.path.exists(utils_path)
-  src_root = os.path.dirname(utils_path)
-  include_path = os.path.join(src_root, 'include')
-  assert os.path.exists(include_path)
-  docs_path = os.path.join(src_root, 'docs')
-  assert os.path.exists(docs_path)
-  macro_test_path = os.path.join(src_root, 'test', 'std', 'language.support',
-                            'support.limits', 'support.limits.general')
-  assert os.path.exists(macro_test_path)
-  assert os.path.exists(os.path.join(macro_test_path, 'version.version.compile.pass.cpp'))
-  return script_name, src_root, include_path, docs_path, macro_test_path
+    utils_path = os.path.dirname(os.path.abspath(__file__))
+    script_name = os.path.basename(__file__)
+    assert os.path.exists(utils_path)
+    src_root = os.path.dirname(utils_path)
+    include_path = os.path.join(src_root, "include")
+    assert os.path.exists(include_path)
+    docs_path = os.path.join(src_root, "docs")
+    assert os.path.exists(docs_path)
+    macro_test_path = os.path.join(
+        src_root,
+        "test",
+        "std",
+        "language.support",
+        "support.limits",
+        "support.limits.general",
+    )
+    assert os.path.exists(macro_test_path)
+    assert os.path.exists(
+        os.path.join(macro_test_path, "version.version.compile.pass.cpp")
+    )
+    return script_name, src_root, include_path, docs_path, macro_test_path
+
 
 script_name, source_root, include_path, docs_path, macro_test_path = get_libcxx_paths()
 
+
 def has_header(h):
-  h_path = os.path.join(include_path, h)
-  return os.path.exists(h_path)
+    h_path = os.path.join(include_path, h)
+    return os.path.exists(h_path)
+
 
 def add_version_header(tc):
-  tc["headers"].append("version")
-  return tc
+    tc["headers"].append("version")
+    return tc
+
 
 # ================  ============================================================
 # Field             Description
@@ -59,739 +72,978 @@
 #                   you've fully implemented the feature, you should remove
 #                   this field.
 # ================  ============================================================
-feature_test_macros = [ add_version_header(x) for x in [
-  {
-    "name": "__cpp_lib_adaptor_iterator_pair_constructor",
-    "values": { "c++2b": 202106 },
-    "headers": ["queue", "stack"],
-  }, {
-    "name": "__cpp_lib_addressof_constexpr",
-    "values": { "c++17": 201603 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_allocate_at_least",
-    "values": { "c++2b": 202106 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_allocator_traits_is_always_equal",
-    "values": { "c++17": 201411 },
-    "headers": ["deque", "forward_list", "list", "map", "memory", "scoped_allocator", "set", "string", "unordered_map", "unordered_set", "vector"],
-  }, {
-    "name": "__cpp_lib_any",
-    "values": { "c++17": 201606 },
-    "headers": ["any"],
-  }, {
-    "name": "__cpp_lib_apply",
-    "values": { "c++17": 201603 },
-    "headers": ["tuple"],
-  }, {
-    "name": "__cpp_lib_array_constexpr",
-    "values": { "c++17": 201603, "c++20": 201811 },
-    "headers": ["array", "iterator"],
-  }, {
-    "name": "__cpp_lib_as_const",
-    "values": { "c++17": 201510 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_associative_heterogeneous_erasure",
-    "values": { "c++2b": 202110 },
-    "headers": ["map", "set", "unordered_map", "unordered_set"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_assume_aligned",
-    "values": { "c++20": 201811 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_atomic_flag_test",
-    "values": { "c++20": 201907 },
-    "headers": ["atomic"],
-  }, {
-    "name": "__cpp_lib_atomic_float",
-    "values": { "c++20": 201711 },
-    "headers": ["atomic"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_atomic_is_always_lock_free",
-    "values": { "c++17": 201603 },
-    "headers": ["atomic"],
-  }, {
-    "name": "__cpp_lib_atomic_lock_free_type_aliases",
-    "values": { "c++20": 201907 },
-    "headers": ["atomic"],
-  }, {
-    "name": "__cpp_lib_atomic_ref",
-    "values": { "c++20": 201806 },
-    "headers": ["atomic"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_atomic_shared_ptr",
-    "values": { "c++20": 201711 },
-    "headers": ["atomic"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_atomic_value_initialization",
-    "values": { "c++20": 201911 },
-    "headers": ["atomic", "memory"],
-  }, {
-    "name": "__cpp_lib_atomic_wait",
-    "values": { "c++20": 201907 },
-    "headers": ["atomic"],
-    "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-    "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-  }, {
-    "name": "__cpp_lib_barrier",
-    "values": { "c++20": 201907 },
-    "headers": ["barrier"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-  }, {
-    "name": "__cpp_lib_bind_back",
-    "values": { "c++2b": 202202 },
-    "headers": ["functional"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_bind_front",
-    "values": { "c++20": 201907 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_bit_cast",
-    "values": { "c++20": 201806 },
-    "headers": ["bit"],
-  }, {
-    "name": "__cpp_lib_bitops",
-    "values": { "c++20": 201907 },
-    "headers": ["bit"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_bool_constant",
-    "values": { "c++17": 201505 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_bounded_array_traits",
-    "values": { "c++20": 201902 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_boyer_moore_searcher",
-    "values": { "c++17": 201603 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_byte",
-    "values": { "c++17": 201603 },
-    "headers": ["cstddef"],
-  }, {
-    "name": "__cpp_lib_byteswap",
-    "values": { "c++2b": 202110 },
-    "headers": ["bit"],
-  }, {
-    "name": "__cpp_lib_char8_t",
-    "values": { "c++20": 201907 },
-    "headers": ["atomic", "filesystem", "istream", "limits", "locale", "ostream", "string", "string_view"],
-    "test_suite_guard": "defined(__cpp_char8_t)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_CHAR8_T)",
-  }, {
-    "name": "__cpp_lib_chrono",
-    "values": { "c++17": 201611 },
-    "headers": ["chrono"],
-  }, {
-    "name": "__cpp_lib_chrono_udls",
-    "values": { "c++14": 201304 },
-    "headers": ["chrono"],
-  }, {
-    "name": "__cpp_lib_clamp",
-    "values": { "c++17": 201603 },
-    "headers": ["algorithm"],
-  }, {
-    "name": "__cpp_lib_complex_udls",
-    "values": { "c++14": 201309 },
-    "headers": ["complex"],
-  }, {
-    "name": "__cpp_lib_concepts",
-    "values": { "c++20": 202002 },
-    "headers": ["concepts"],
-  }, {
-    "name": "__cpp_lib_constexpr_algorithms",
-    "values": { "c++20": 201806 },
-    "headers": ["algorithm", "utility"],
-  }, {
-    "name": "__cpp_lib_constexpr_bitset",
-    "values": { "c++2b": 202207 },
-    "headers": ["bitset"],
-  }, {
-    "name": "__cpp_lib_constexpr_charconv",
-    "values": { "c++2b": 202207 },
-    "headers": ["charconv"],
-  }, {
-    "name": "__cpp_lib_constexpr_cmath",
-    "values": { "c++2b": 202202 },
-    "headers": ["cmath", "cstdlib"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_constexpr_complex",
-    "values": { "c++20": 201711 },
-    "headers": ["complex"],
-  }, {
-    "name": "__cpp_lib_constexpr_dynamic_alloc",
-    "values": { "c++20": 201907 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_constexpr_functional",
-    "values": { "c++20": 201907 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_constexpr_iterator",
-    "values": { "c++20": 201811 },
-    "headers": ["iterator"],
-  }, {
-    "name": "__cpp_lib_constexpr_memory",
-    "values": { "c++20": 201811, "c++2b": 202202 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_constexpr_numeric",
-    "values": { "c++20": 201911 },
-    "headers": ["numeric"],
-  }, {
-    "name": "__cpp_lib_constexpr_string",
-    "values": { "c++20": 201907 },
-    "headers": ["string"],
-  }, {
-    "name": "__cpp_lib_constexpr_string_view",
-    "values": { "c++20": 201811 },
-    "headers": ["string_view"],
-  }, {
-    "name": "__cpp_lib_constexpr_tuple",
-    "values": { "c++20": 201811 },
-    "headers": ["tuple"],
-  }, {
-    "name": "__cpp_lib_constexpr_typeinfo",
-    "values": { "c++2b": 202106 },
-    "headers": ["typeinfo"],
-  }, {
-    "name": "__cpp_lib_constexpr_utility",
-    "values": { "c++20": 201811 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_constexpr_vector",
-    "values": { "c++20": 201907 },
-    "headers": ["vector"],
-  }, {
-    "name": "__cpp_lib_coroutine",
-    "values": { "c++20": 201902 },
-    "headers": ["coroutine"],
-  }, {
-    "name": "__cpp_lib_destroying_delete",
-    "values": { "c++20": 201806 },
-    "headers": ["new"],
-    "test_suite_guard": "TEST_STD_VER > 17 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L",
-    "libcxx_guard": "_LIBCPP_STD_VER >= 20 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L",
-  }, {
-    "name": "__cpp_lib_enable_shared_from_this",
-    "values": { "c++17": 201603 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_endian",
-    "values": { "c++20": 201907 },
-    "headers": ["bit"],
-  }, {
-    "name": "__cpp_lib_erase_if",
-    "values": { "c++20": 202002 },
-    "headers": ["deque", "forward_list", "list", "map", "set", "string", "unordered_map", "unordered_set", "vector"],
-  }, {
-    "name": "__cpp_lib_exchange_function",
-    "values": { "c++14": 201304 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_execution",
-    "values": { "c++17": 201603, "c++20": 201902 },
-    "headers": ["execution"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_expected",
-    "values": { "c++2b": 202211 },
-    "headers": ["expected"],
-  }, {
-    "name": "__cpp_lib_filesystem",
-    "values": { "c++17": 201703 },
-    "headers": ["filesystem"],
-    "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_FILESYSTEM)",
-    "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_FILESYSTEM)"
-  }, {
-    "name": "__cpp_lib_format",
-    "values": {
-        # "c++20": 201907 Not implemented P1361R2 Integration of chrono with text formatting
-        # "c++20": 202106 Fully implemented
-        # "c++20": 202110 Not implemented P2372R3 Fixing locale handling in chrono formatters
-        "c++20": 202106,
-        # "c++23": 202207, Not implemented P2419R2 Clarify handling of encodings in localized formatting of chrono types
-        },
-    "headers": ["format"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_format_ranges",
-    "values": { "c++2b": 202207 },
-    "headers": ["format"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-  }, {
-    "name": "__cpp_lib_formatters",
-    "values": { "c++2b": 202302 },
-    "headers": ["stacktrace", "thread"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_forward_like",
-    "values": { "c++2b": 202207 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_gcd_lcm",
-    "values": { "c++17": 201606 },
-    "headers": ["numeric"],
-  }, {
-    "name": "__cpp_lib_generic_associative_lookup",
-    "values": { "c++14": 201304 },
-    "headers": ["map", "set"],
-  }, {
-    "name": "__cpp_lib_generic_unordered_lookup",
-    "values": { "c++20": 201811 },
-    "headers": ["unordered_map", "unordered_set"],
-  }, {
-    "name": "__cpp_lib_hardware_interference_size",
-    "values": { "c++17": 201703 },
-    "test_suite_guard": "defined(__GCC_DESTRUCTIVE_SIZE) && defined(__GCC_CONSTRUCTIVE_SIZE)",
-    "libcxx_guard": "defined(__GCC_DESTRUCTIVE_SIZE) && defined(__GCC_CONSTRUCTIVE_SIZE)",
-    "headers": ["new"],
-  }, {
-    "name": "__cpp_lib_has_unique_object_representations",
-    "values": { "c++17": 201606 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_hypot",
-    "values": { "c++17": 201603 },
-    "headers": ["cmath"],
-  }, {
-    "name": "__cpp_lib_incomplete_container_elements",
-    "values": { "c++17": 201505 },
-    "headers": ["forward_list", "list", "vector"],
-  }, {
-    "name": "__cpp_lib_int_pow2",
-    "values": { "c++20": 202002 },
-    "headers": ["bit"],
-  }, {
-    "name": "__cpp_lib_integer_comparison_functions",
-    "values": { "c++20": 202002 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_integer_sequence",
-    "values": { "c++14": 201304 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_integral_constant_callable",
-    "values": { "c++14": 201304 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_interpolate",
-    "values": { "c++20": 201902 },
-    "headers": ["cmath", "numeric"],
-  }, {
-    "name": "__cpp_lib_invoke",
-    "values": { "c++17": 201411 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_invoke_r",
-    "values": { "c++2b": 202106 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_is_aggregate",
-    "values": { "c++17": 201703 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_constant_evaluated",
-    "values": { "c++20": 201811 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_final",
-    "values": { "c++14": 201402 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_invocable",
-    "values": { "c++17": 201703 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_layout_compatible",
-    "values": { "c++20": 201907 },
-    "headers": ["type_traits"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_is_nothrow_convertible",
-    "values": { "c++20": 201806 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_null_pointer",
-    "values": { "c++14": 201309 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_pointer_interconvertible",
-    "values": { "c++20": 201907 },
-    "headers": ["type_traits"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_is_scoped_enum",
-    "values": { "c++2b": 202011 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_is_swappable",
-    "values": { "c++17": 201603 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_jthread",
-    "values": { "c++20": 201911 },
-    "headers": ["stop_token", "thread"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_latch",
-    "values": { "c++20": 201907 },
-    "headers": ["latch"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-  }, {
-    "name": "__cpp_lib_launder",
-    "values": { "c++17": 201606 },
-    "headers": ["new"],
-  }, {
-    "name": "__cpp_lib_list_remove_return_type",
-    "values": { "c++20": 201806 },
-    "headers": ["forward_list", "list"],
-  }, {
-    "name": "__cpp_lib_logical_traits",
-    "values": { "c++17": 201510 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_make_from_tuple",
-    "values": { "c++17": 201606 },
-    "headers": ["tuple"],
-  }, {
-    "name": "__cpp_lib_make_reverse_iterator",
-    "values": { "c++14": 201402 },
-    "headers": ["iterator"],
-  }, {
-    "name": "__cpp_lib_make_unique",
-    "values": { "c++14": 201304 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_map_try_emplace",
-    "values": { "c++17": 201411 },
-    "headers": ["map"],
-  }, {
-    "name": "__cpp_lib_math_constants",
-    "values": { "c++20": 201907 },
-    "headers": ["numbers"],
-  }, {
-    "name": "__cpp_lib_math_special_functions",
-    "values": { "c++17": 201603 },
-    "headers": ["cmath"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_mdspan",
-    "values": { "c++2b": 202207 },
-    "headers": ["mdspan"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_memory_resource",
-    "values": { "c++17": 201603 },
-    "headers": ["memory_resource"],
-  }, {
-    "name": "__cpp_lib_move_iterator_concept",
-    "values": { "c++20": 202207 },
-    "headers": ["iterator"],
-   }, {
-    "name": "__cpp_lib_move_only_function",
-    "values": { "c++2b": 202110 },
-    "headers": ["functional"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_node_extract",
-    "values": { "c++17": 201606 },
-    "headers": ["map", "set", "unordered_map", "unordered_set"],
-  }, {
-    "name": "__cpp_lib_nonmember_container_access",
-    "values": { "c++17": 201411 },
-    "headers": ["array", "deque", "forward_list", "iterator", "list", "map", "regex", "set", "string", "unordered_map", "unordered_set", "vector"],
-  }, {
-    "name": "__cpp_lib_not_fn",
-    "values": { "c++17": 201603 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_null_iterators",
-    "values": { "c++14": 201304 },
-    "headers": ["iterator"],
-  }, {
-    "name": "__cpp_lib_optional",
-    "values": { "c++17": 201606, "c++2b": 202110 },
-    "headers": ["optional"],
-  }, {
-    "name": "__cpp_lib_out_ptr",
-    "values": { "c++2b": 202106 },
-    "headers": ["memory"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_parallel_algorithm",
-    "values": { "c++17": 201603 },
-    "headers": ["algorithm", "numeric"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_polymorphic_allocator",
-    "values": { "c++20": 201902 },
-    "headers": ["memory_resource"],
-  }, {
-    "name": "__cpp_lib_quoted_string_io",
-    "values": { "c++14": 201304 },
-    "headers": ["iomanip"],
-  }, {
-    "name": "__cpp_lib_ranges",
-    "values": { "c++20": 202106 },
-    "headers": ["algorithm", "functional", "iterator", "memory", "ranges"],
-  }, {
-    "name": "__cpp_lib_ranges_as_rvalue",
-    "values": { "c++2b": 202207 },
-    "headers": ["ranges"],
-  }, {
-    "name": "__cpp_lib_ranges_chunk",
-    "values": { "c++2b": 202202 },
-    "headers": ["ranges"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_chunk_by",
-    "values": { "c++2b": 202202 },
-    "headers": ["ranges"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_iota",
-    "values": { "c++2b": 202202 },
-    "headers": ["numeric"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_join_with",
-    "values": { "c++2b": 202202 },
-    "headers": ["ranges"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_slide",
-    "values": { "c++2b": 202202 },
-    "headers": ["ranges"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_starts_ends_with",
-    "values": { "c++2b": 202106 },
-    "headers": ["algorithm"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_to_container",
-    "values": { "c++2b": 202202 },
-    "headers": ["deque", "forward_list", "list", "map", "priority_queue", "queue", "set", "stack", "string", "unordered_map", "unordered_set", "vector"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ranges_zip",
-    "values": { "c++2b": 202110 },
-    "headers": ["ranges", "tuple", "utility"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_raw_memory_algorithms",
-    "values": { "c++17": 201606 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_reference_from_temporary",
-    "values": { "c++2b": 202202 },
-    "headers": ["type_traits"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_remove_cvref",
-    "values": { "c++20": 201711 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_result_of_sfinae",
-    "values": { "c++14": 201210 },
-    "headers": ["functional", "type_traits"],
-  }, {
-    "name": "__cpp_lib_robust_nonmodifying_seq_ops",
-    "values": { "c++14": 201304 },
-    "headers": ["algorithm"],
-  }, {
-    "name": "__cpp_lib_sample",
-    "values": { "c++17": 201603 },
-    "headers": ["algorithm"],
-  }, {
-    "name": "__cpp_lib_scoped_lock",
-    "values": { "c++17": 201703 },
-    "headers": ["mutex"],
-  }, {
-    "name": "__cpp_lib_semaphore",
-    "values": { "c++20": 201907 },
-    "headers": ["semaphore"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
-  }, {
-    "name": "__cpp_lib_shared_mutex",
-    "values": { "c++17": 201505 },
-    "headers": ["shared_mutex"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
-  }, {
-    "name": "__cpp_lib_shared_ptr_arrays",
-    "values": { "c++17": 201611, "c++20": 201707 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_shared_ptr_weak_type",
-    "values": { "c++17": 201606 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_shared_timed_mutex",
-    "values": { "c++14": 201402 },
-    "headers": ["shared_mutex"],
-    "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
-    "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
-  }, {
-    "name": "__cpp_lib_shift",
-    "values": { "c++20": 201806 },
-    "headers": ["algorithm"],
-  }, {
-    "name": "__cpp_lib_smart_ptr_for_overwrite",
-    "values": { "c++20": 202002 },
-    "headers": ["memory"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_source_location",
-    "values": { "c++20": 201907 },
-    "headers": ["source_location"],
-    "test_suite_guard": "__has_builtin(__builtin_source_location) && !(defined(TEST_APPLE_CLANG_VER) && TEST_APPLE_CLANG_VER <= 1403)",
-    "libcxx_guard": "__has_builtin(__builtin_source_location) && !(defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER <= 1403)",
-  }, {
-    "name": "__cpp_lib_span",
-    "values": { "c++20": 202002 },
-    "headers": ["span"],
-  }, {
-    "name": "__cpp_lib_spanstream",
-    "values": { "c++2b": 202106 },
-    "headers": ["spanstream"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_ssize",
-    "values": { "c++20": 201902 },
-    "headers": ["iterator"],
-  }, {
-    "name": "__cpp_lib_stacktrace",
-    "values": { "c++2b": 202011 },
-    "headers": ["stacktrace"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_starts_ends_with",
-    "values": { "c++20": 201711 },
-    "headers": ["string", "string_view"],
-  }, {
-    "name": "__cpp_lib_stdatomic_h",
-    "values": { "c++2b": 202011 },
-    "headers": ["stdatomic.h"],
-  }, {
-    "name": "__cpp_lib_string_contains",
-    "values": { "c++2b": 202011 },
-    "headers": ["string", "string_view"],
-  }, {
-    "name": "__cpp_lib_string_resize_and_overwrite",
-    "values": { "c++2b": 202110 },
-    "headers": ["string"],
-  }, {
-    "name": "__cpp_lib_string_udls",
-    "values": { "c++14": 201304 },
-    "headers": ["string"],
-  }, {
-    "name": "__cpp_lib_string_view",
-    "values": { "c++17": 201606, "c++20": 201803 },
-    "headers": ["string", "string_view"],
-  }, {
-    "name": "__cpp_lib_syncbuf",
-    "values": { "c++20": 201803 },
-    "headers": ["syncstream"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_three_way_comparison",
-    "values": { "c++20": 201907 },
-    "headers": ["compare"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_to_address",
-    "values": { "c++20": 201711 },
-    "headers": ["memory"],
-  }, {
-    "name": "__cpp_lib_to_array",
-    "values": { "c++20": 201907 },
-    "headers": ["array"],
-  }, {
-    "name": "__cpp_lib_to_chars",
-    "values": { "c++17": 201611 },
-    "headers": ["charconv"],
-    "unimplemented": True,
-  }, {
-    "name": "__cpp_lib_to_underlying",
-    "values": { "c++2b": 202102 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_transformation_trait_aliases",
-    "values": { "c++14": 201304 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_transparent_operators",
-    "values": { "c++14": 201210, "c++17": 201510 },
-    "headers": ["functional", "memory"],
-  }, {
-    "name": "__cpp_lib_tuple_element_t",
-    "values": { "c++14": 201402 },
-    "headers": ["tuple"],
-  }, {
-    "name": "__cpp_lib_tuples_by_type",
-    "values": { "c++14": 201304 },
-    "headers": ["tuple", "utility"],
-  }, {
-    "name": "__cpp_lib_type_identity",
-    "values": { "c++20": 201806 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_type_trait_variable_templates",
-    "values": { "c++17": 201510 },
-    "headers": ["type_traits"],
-  }, {
-    "name": "__cpp_lib_uncaught_exceptions",
-    "values": { "c++17": 201411 },
-    "headers": ["exception"],
-  }, {
-    "name": "__cpp_lib_unordered_map_try_emplace",
-    "values": { "c++17": 201411 },
-    "headers": ["unordered_map"],
-  }, {
-    "name": "__cpp_lib_unreachable",
-    "values": { "c++2b": 202202 },
-    "headers": ["utility"],
-  }, {
-    "name": "__cpp_lib_unwrap_ref",
-    "values": { "c++20": 201811 },
-    "headers": ["functional"],
-  }, {
-    "name": "__cpp_lib_variant",
-    "values": { "c++17": 202102 },
-    "headers": ["variant"],
-  }, {
-    "name": "__cpp_lib_void_t",
-    "values": { "c++17": 201411 },
-    "headers": ["type_traits"],
-  }
-]]
+feature_test_macros = [
+    add_version_header(x)
+    for x in [
+        {
+            "name": "__cpp_lib_adaptor_iterator_pair_constructor",
+            "values": {"c++2b": 202106},
+            "headers": ["queue", "stack"],
+        },
+        {
+            "name": "__cpp_lib_addressof_constexpr",
+            "values": {"c++17": 201603},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_allocate_at_least",
+            "values": {"c++2b": 202106},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_allocator_traits_is_always_equal",
+            "values": {"c++17": 201411},
+            "headers": [
+                "deque",
+                "forward_list",
+                "list",
+                "map",
+                "memory",
+                "scoped_allocator",
+                "set",
+                "string",
+                "unordered_map",
+                "unordered_set",
+                "vector",
+            ],
+        },
+        {
+            "name": "__cpp_lib_any",
+            "values": {"c++17": 201606},
+            "headers": ["any"],
+        },
+        {
+            "name": "__cpp_lib_apply",
+            "values": {"c++17": 201603},
+            "headers": ["tuple"],
+        },
+        {
+            "name": "__cpp_lib_array_constexpr",
+            "values": {"c++17": 201603, "c++20": 201811},
+            "headers": ["array", "iterator"],
+        },
+        {
+            "name": "__cpp_lib_as_const",
+            "values": {"c++17": 201510},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_associative_heterogeneous_erasure",
+            "values": {"c++2b": 202110},
+            "headers": ["map", "set", "unordered_map", "unordered_set"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_assume_aligned",
+            "values": {"c++20": 201811},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_atomic_flag_test",
+            "values": {"c++20": 201907},
+            "headers": ["atomic"],
+        },
+        {
+            "name": "__cpp_lib_atomic_float",
+            "values": {"c++20": 201711},
+            "headers": ["atomic"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_atomic_is_always_lock_free",
+            "values": {"c++17": 201603},
+            "headers": ["atomic"],
+        },
+        {
+            "name": "__cpp_lib_atomic_lock_free_type_aliases",
+            "values": {"c++20": 201907},
+            "headers": ["atomic"],
+        },
+        {
+            "name": "__cpp_lib_atomic_ref",
+            "values": {"c++20": 201806},
+            "headers": ["atomic"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_atomic_shared_ptr",
+            "values": {"c++20": 201711},
+            "headers": ["atomic"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_atomic_value_initialization",
+            "values": {"c++20": 201911},
+            "headers": ["atomic", "memory"],
+        },
+        {
+            "name": "__cpp_lib_atomic_wait",
+            "values": {"c++20": 201907},
+            "headers": ["atomic"],
+            "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+            "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+        },
+        {
+            "name": "__cpp_lib_barrier",
+            "values": {"c++20": 201907},
+            "headers": ["barrier"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+        },
+        {
+            "name": "__cpp_lib_bind_back",
+            "values": {"c++2b": 202202},
+            "headers": ["functional"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_bind_front",
+            "values": {"c++20": 201907},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_bit_cast",
+            "values": {"c++20": 201806},
+            "headers": ["bit"],
+        },
+        {
+            "name": "__cpp_lib_bitops",
+            "values": {"c++20": 201907},
+            "headers": ["bit"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_bool_constant",
+            "values": {"c++17": 201505},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_bounded_array_traits",
+            "values": {"c++20": 201902},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_boyer_moore_searcher",
+            "values": {"c++17": 201603},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_byte",
+            "values": {"c++17": 201603},
+            "headers": ["cstddef"],
+        },
+        {
+            "name": "__cpp_lib_byteswap",
+            "values": {"c++2b": 202110},
+            "headers": ["bit"],
+        },
+        {
+            "name": "__cpp_lib_char8_t",
+            "values": {"c++20": 201907},
+            "headers": [
+                "atomic",
+                "filesystem",
+                "istream",
+                "limits",
+                "locale",
+                "ostream",
+                "string",
+                "string_view",
+            ],
+            "test_suite_guard": "defined(__cpp_char8_t)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_CHAR8_T)",
+        },
+        {
+            "name": "__cpp_lib_chrono",
+            "values": {"c++17": 201611},
+            "headers": ["chrono"],
+        },
+        {
+            "name": "__cpp_lib_chrono_udls",
+            "values": {"c++14": 201304},
+            "headers": ["chrono"],
+        },
+        {
+            "name": "__cpp_lib_clamp",
+            "values": {"c++17": 201603},
+            "headers": ["algorithm"],
+        },
+        {
+            "name": "__cpp_lib_complex_udls",
+            "values": {"c++14": 201309},
+            "headers": ["complex"],
+        },
+        {
+            "name": "__cpp_lib_concepts",
+            "values": {"c++20": 202002},
+            "headers": ["concepts"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_algorithms",
+            "values": {"c++20": 201806},
+            "headers": ["algorithm", "utility"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_bitset",
+            "values": {"c++2b": 202207},
+            "headers": ["bitset"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_charconv",
+            "values": {"c++2b": 202207},
+            "headers": ["charconv"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_cmath",
+            "values": {"c++2b": 202202},
+            "headers": ["cmath", "cstdlib"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_constexpr_complex",
+            "values": {"c++20": 201711},
+            "headers": ["complex"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_dynamic_alloc",
+            "values": {"c++20": 201907},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_functional",
+            "values": {"c++20": 201907},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_iterator",
+            "values": {"c++20": 201811},
+            "headers": ["iterator"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_memory",
+            "values": {"c++20": 201811, "c++2b": 202202},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_numeric",
+            "values": {"c++20": 201911},
+            "headers": ["numeric"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_string",
+            "values": {"c++20": 201907},
+            "headers": ["string"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_string_view",
+            "values": {"c++20": 201811},
+            "headers": ["string_view"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_tuple",
+            "values": {"c++20": 201811},
+            "headers": ["tuple"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_typeinfo",
+            "values": {"c++2b": 202106},
+            "headers": ["typeinfo"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_utility",
+            "values": {"c++20": 201811},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_constexpr_vector",
+            "values": {"c++20": 201907},
+            "headers": ["vector"],
+        },
+        {
+            "name": "__cpp_lib_coroutine",
+            "values": {"c++20": 201902},
+            "headers": ["coroutine"],
+        },
+        {
+            "name": "__cpp_lib_destroying_delete",
+            "values": {"c++20": 201806},
+            "headers": ["new"],
+            "test_suite_guard": "TEST_STD_VER > 17 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L",
+            "libcxx_guard": "_LIBCPP_STD_VER >= 20 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L",
+        },
+        {
+            "name": "__cpp_lib_enable_shared_from_this",
+            "values": {"c++17": 201603},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_endian",
+            "values": {"c++20": 201907},
+            "headers": ["bit"],
+        },
+        {
+            "name": "__cpp_lib_erase_if",
+            "values": {"c++20": 202002},
+            "headers": [
+                "deque",
+                "forward_list",
+                "list",
+                "map",
+                "set",
+                "string",
+                "unordered_map",
+                "unordered_set",
+                "vector",
+            ],
+        },
+        {
+            "name": "__cpp_lib_exchange_function",
+            "values": {"c++14": 201304},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_execution",
+            "values": {"c++17": 201603, "c++20": 201902},
+            "headers": ["execution"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_expected",
+            "values": {"c++2b": 202211},
+            "headers": ["expected"],
+        },
+        {
+            "name": "__cpp_lib_filesystem",
+            "values": {"c++17": 201703},
+            "headers": ["filesystem"],
+            "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_FILESYSTEM)",
+            "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_HAS_NO_FILESYSTEM)",
+        },
+        {
+            "name": "__cpp_lib_format",
+            "values": {
+                # "c++20": 201907 Not implemented P1361R2 Integration of chrono with text formatting
+                # "c++20": 202106 Fully implemented
+                # "c++20": 202110 Not implemented P2372R3 Fixing locale handling in chrono formatters
+                "c++20": 202106,
+                # "c++23": 202207, Not implemented P2419R2 Clarify handling of encodings in localized formatting of chrono types
+            },
+            "headers": ["format"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_format_ranges",
+            "values": {"c++2b": 202207},
+            "headers": ["format"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+        },
+        {
+            "name": "__cpp_lib_formatters",
+            "values": {"c++2b": 202302},
+            "headers": ["stacktrace", "thread"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_forward_like",
+            "values": {"c++2b": 202207},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_gcd_lcm",
+            "values": {"c++17": 201606},
+            "headers": ["numeric"],
+        },
+        {
+            "name": "__cpp_lib_generic_associative_lookup",
+            "values": {"c++14": 201304},
+            "headers": ["map", "set"],
+        },
+        {
+            "name": "__cpp_lib_generic_unordered_lookup",
+            "values": {"c++20": 201811},
+            "headers": ["unordered_map", "unordered_set"],
+        },
+        {
+            "name": "__cpp_lib_hardware_interference_size",
+            "values": {"c++17": 201703},
+            "test_suite_guard": "defined(__GCC_DESTRUCTIVE_SIZE) && defined(__GCC_CONSTRUCTIVE_SIZE)",
+            "libcxx_guard": "defined(__GCC_DESTRUCTIVE_SIZE) && defined(__GCC_CONSTRUCTIVE_SIZE)",
+            "headers": ["new"],
+        },
+        {
+            "name": "__cpp_lib_has_unique_object_representations",
+            "values": {"c++17": 201606},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_hypot",
+            "values": {"c++17": 201603},
+            "headers": ["cmath"],
+        },
+        {
+            "name": "__cpp_lib_incomplete_container_elements",
+            "values": {"c++17": 201505},
+            "headers": ["forward_list", "list", "vector"],
+        },
+        {
+            "name": "__cpp_lib_int_pow2",
+            "values": {"c++20": 202002},
+            "headers": ["bit"],
+        },
+        {
+            "name": "__cpp_lib_integer_comparison_functions",
+            "values": {"c++20": 202002},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_integer_sequence",
+            "values": {"c++14": 201304},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_integral_constant_callable",
+            "values": {"c++14": 201304},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_interpolate",
+            "values": {"c++20": 201902},
+            "headers": ["cmath", "numeric"],
+        },
+        {
+            "name": "__cpp_lib_invoke",
+            "values": {"c++17": 201411},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_invoke_r",
+            "values": {"c++2b": 202106},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_is_aggregate",
+            "values": {"c++17": 201703},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_constant_evaluated",
+            "values": {"c++20": 201811},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_final",
+            "values": {"c++14": 201402},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_invocable",
+            "values": {"c++17": 201703},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_layout_compatible",
+            "values": {"c++20": 201907},
+            "headers": ["type_traits"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_is_nothrow_convertible",
+            "values": {"c++20": 201806},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_null_pointer",
+            "values": {"c++14": 201309},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_pointer_interconvertible",
+            "values": {"c++20": 201907},
+            "headers": ["type_traits"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_is_scoped_enum",
+            "values": {"c++2b": 202011},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_is_swappable",
+            "values": {"c++17": 201603},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_jthread",
+            "values": {"c++20": 201911},
+            "headers": ["stop_token", "thread"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS)",
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_latch",
+            "values": {"c++20": 201907},
+            "headers": ["latch"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+        },
+        {
+            "name": "__cpp_lib_launder",
+            "values": {"c++17": 201606},
+            "headers": ["new"],
+        },
+        {
+            "name": "__cpp_lib_list_remove_return_type",
+            "values": {"c++20": 201806},
+            "headers": ["forward_list", "list"],
+        },
+        {
+            "name": "__cpp_lib_logical_traits",
+            "values": {"c++17": 201510},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_make_from_tuple",
+            "values": {"c++17": 201606},
+            "headers": ["tuple"],
+        },
+        {
+            "name": "__cpp_lib_make_reverse_iterator",
+            "values": {"c++14": 201402},
+            "headers": ["iterator"],
+        },
+        {
+            "name": "__cpp_lib_make_unique",
+            "values": {"c++14": 201304},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_map_try_emplace",
+            "values": {"c++17": 201411},
+            "headers": ["map"],
+        },
+        {
+            "name": "__cpp_lib_math_constants",
+            "values": {"c++20": 201907},
+            "headers": ["numbers"],
+        },
+        {
+            "name": "__cpp_lib_math_special_functions",
+            "values": {"c++17": 201603},
+            "headers": ["cmath"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_mdspan",
+            "values": {"c++2b": 202207},
+            "headers": ["mdspan"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_memory_resource",
+            "values": {"c++17": 201603},
+            "headers": ["memory_resource"],
+        },
+        {
+            "name": "__cpp_lib_move_iterator_concept",
+            "values": {"c++20": 202207},
+            "headers": ["iterator"],
+        },
+        {
+            "name": "__cpp_lib_move_only_function",
+            "values": {"c++2b": 202110},
+            "headers": ["functional"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_node_extract",
+            "values": {"c++17": 201606},
+            "headers": ["map", "set", "unordered_map", "unordered_set"],
+        },
+        {
+            "name": "__cpp_lib_nonmember_container_access",
+            "values": {"c++17": 201411},
+            "headers": [
+                "array",
+                "deque",
+                "forward_list",
+                "iterator",
+                "list",
+                "map",
+                "regex",
+                "set",
+                "string",
+                "unordered_map",
+                "unordered_set",
+                "vector",
+            ],
+        },
+        {
+            "name": "__cpp_lib_not_fn",
+            "values": {"c++17": 201603},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_null_iterators",
+            "values": {"c++14": 201304},
+            "headers": ["iterator"],
+        },
+        {
+            "name": "__cpp_lib_optional",
+            "values": {"c++17": 201606, "c++2b": 202110},
+            "headers": ["optional"],
+        },
+        {
+            "name": "__cpp_lib_out_ptr",
+            "values": {"c++2b": 202106},
+            "headers": ["memory"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_parallel_algorithm",
+            "values": {"c++17": 201603},
+            "headers": ["algorithm", "numeric"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_polymorphic_allocator",
+            "values": {"c++20": 201902},
+            "headers": ["memory_resource"],
+        },
+        {
+            "name": "__cpp_lib_quoted_string_io",
+            "values": {"c++14": 201304},
+            "headers": ["iomanip"],
+        },
+        {
+            "name": "__cpp_lib_ranges",
+            "values": {"c++20": 202106},
+            "headers": ["algorithm", "functional", "iterator", "memory", "ranges"],
+        },
+        {
+            "name": "__cpp_lib_ranges_as_rvalue",
+            "values": {"c++2b": 202207},
+            "headers": ["ranges"],
+        },
+        {
+            "name": "__cpp_lib_ranges_chunk",
+            "values": {"c++2b": 202202},
+            "headers": ["ranges"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_chunk_by",
+            "values": {"c++2b": 202202},
+            "headers": ["ranges"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_iota",
+            "values": {"c++2b": 202202},
+            "headers": ["numeric"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_join_with",
+            "values": {"c++2b": 202202},
+            "headers": ["ranges"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_slide",
+            "values": {"c++2b": 202202},
+            "headers": ["ranges"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_starts_ends_with",
+            "values": {"c++2b": 202106},
+            "headers": ["algorithm"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_to_container",
+            "values": {"c++2b": 202202},
+            "headers": [
+                "deque",
+                "forward_list",
+                "list",
+                "map",
+                "priority_queue",
+                "queue",
+                "set",
+                "stack",
+                "string",
+                "unordered_map",
+                "unordered_set",
+                "vector",
+            ],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ranges_zip",
+            "values": {"c++2b": 202110},
+            "headers": ["ranges", "tuple", "utility"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_raw_memory_algorithms",
+            "values": {"c++17": 201606},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_reference_from_temporary",
+            "values": {"c++2b": 202202},
+            "headers": ["type_traits"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_remove_cvref",
+            "values": {"c++20": 201711},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_result_of_sfinae",
+            "values": {"c++14": 201210},
+            "headers": ["functional", "type_traits"],
+        },
+        {
+            "name": "__cpp_lib_robust_nonmodifying_seq_ops",
+            "values": {"c++14": 201304},
+            "headers": ["algorithm"],
+        },
+        {
+            "name": "__cpp_lib_sample",
+            "values": {"c++17": 201603},
+            "headers": ["algorithm"],
+        },
+        {
+            "name": "__cpp_lib_scoped_lock",
+            "values": {"c++17": 201703},
+            "headers": ["mutex"],
+        },
+        {
+            "name": "__cpp_lib_semaphore",
+            "values": {"c++20": 201907},
+            "headers": ["semaphore"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SYNC)",
+        },
+        {
+            "name": "__cpp_lib_shared_mutex",
+            "values": {"c++17": 201505},
+            "headers": ["shared_mutex"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
+        },
+        {
+            "name": "__cpp_lib_shared_ptr_arrays",
+            "values": {"c++17": 201611, "c++20": 201707},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_shared_ptr_weak_type",
+            "values": {"c++17": 201606},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_shared_timed_mutex",
+            "values": {"c++14": 201402},
+            "headers": ["shared_mutex"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_HAS_NO_SHARED_MUTEX)",
+        },
+        {
+            "name": "__cpp_lib_shift",
+            "values": {"c++20": 201806},
+            "headers": ["algorithm"],
+        },
+        {
+            "name": "__cpp_lib_smart_ptr_for_overwrite",
+            "values": {"c++20": 202002},
+            "headers": ["memory"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_source_location",
+            "values": {"c++20": 201907},
+            "headers": ["source_location"],
+            "test_suite_guard": "__has_builtin(__builtin_source_location) && !(defined(TEST_APPLE_CLANG_VER) && TEST_APPLE_CLANG_VER <= 1403)",
+            "libcxx_guard": "__has_builtin(__builtin_source_location) && !(defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER <= 1403)",
+        },
+        {
+            "name": "__cpp_lib_span",
+            "values": {"c++20": 202002},
+            "headers": ["span"],
+        },
+        {
+            "name": "__cpp_lib_spanstream",
+            "values": {"c++2b": 202106},
+            "headers": ["spanstream"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_ssize",
+            "values": {"c++20": 201902},
+            "headers": ["iterator"],
+        },
+        {
+            "name": "__cpp_lib_stacktrace",
+            "values": {"c++2b": 202011},
+            "headers": ["stacktrace"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_starts_ends_with",
+            "values": {"c++20": 201711},
+            "headers": ["string", "string_view"],
+        },
+        {
+            "name": "__cpp_lib_stdatomic_h",
+            "values": {"c++2b": 202011},
+            "headers": ["stdatomic.h"],
+        },
+        {
+            "name": "__cpp_lib_string_contains",
+            "values": {"c++2b": 202011},
+            "headers": ["string", "string_view"],
+        },
+        {
+            "name": "__cpp_lib_string_resize_and_overwrite",
+            "values": {"c++2b": 202110},
+            "headers": ["string"],
+        },
+        {
+            "name": "__cpp_lib_string_udls",
+            "values": {"c++14": 201304},
+            "headers": ["string"],
+        },
+        {
+            "name": "__cpp_lib_string_view",
+            "values": {"c++17": 201606, "c++20": 201803},
+            "headers": ["string", "string_view"],
+        },
+        {
+            "name": "__cpp_lib_syncbuf",
+            "values": {"c++20": 201803},
+            "headers": ["syncstream"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_three_way_comparison",
+            "values": {"c++20": 201907},
+            "headers": ["compare"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_to_address",
+            "values": {"c++20": 201711},
+            "headers": ["memory"],
+        },
+        {
+            "name": "__cpp_lib_to_array",
+            "values": {"c++20": 201907},
+            "headers": ["array"],
+        },
+        {
+            "name": "__cpp_lib_to_chars",
+            "values": {"c++17": 201611},
+            "headers": ["charconv"],
+            "unimplemented": True,
+        },
+        {
+            "name": "__cpp_lib_to_underlying",
+            "values": {"c++2b": 202102},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_transformation_trait_aliases",
+            "values": {"c++14": 201304},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_transparent_operators",
+            "values": {"c++14": 201210, "c++17": 201510},
+            "headers": ["functional", "memory"],
+        },
+        {
+            "name": "__cpp_lib_tuple_element_t",
+            "values": {"c++14": 201402},
+            "headers": ["tuple"],
+        },
+        {
+            "name": "__cpp_lib_tuples_by_type",
+            "values": {"c++14": 201304},
+            "headers": ["tuple", "utility"],
+        },
+        {
+            "name": "__cpp_lib_type_identity",
+            "values": {"c++20": 201806},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_type_trait_variable_templates",
+            "values": {"c++17": 201510},
+            "headers": ["type_traits"],
+        },
+        {
+            "name": "__cpp_lib_uncaught_exceptions",
+            "values": {"c++17": 201411},
+            "headers": ["exception"],
+        },
+        {
+            "name": "__cpp_lib_unordered_map_try_emplace",
+            "values": {"c++17": 201411},
+            "headers": ["unordered_map"],
+        },
+        {
+            "name": "__cpp_lib_unreachable",
+            "values": {"c++2b": 202202},
+            "headers": ["utility"],
+        },
+        {
+            "name": "__cpp_lib_unwrap_ref",
+            "values": {"c++20": 201811},
+            "headers": ["functional"],
+        },
+        {
+            "name": "__cpp_lib_variant",
+            "values": {"c++17": 202102},
+            "headers": ["variant"],
+        },
+        {
+            "name": "__cpp_lib_void_t",
+            "values": {"c++17": 201411},
+            "headers": ["type_traits"],
+        },
+    ]
+]
 
 assert feature_test_macros == sorted(feature_test_macros, key=lambda tc: tc["name"])
 assert all(tc["headers"] == sorted(tc["headers"]) for tc in feature_test_macros)
-assert all(("libcxx_guard" in tc) == ("test_suite_guard" in tc) for tc in feature_test_macros)
-assert all(all(key in ["name", "values", "headers", "libcxx_guard", "test_suite_guard", "unimplemented"] for key in tc.keys()) for tc in feature_test_macros)
+assert all(
+    ("libcxx_guard" in tc) == ("test_suite_guard" in tc) for tc in feature_test_macros
+)
+assert all(
+    all(
+        key
+        in [
+            "name",
+            "values",
+            "headers",
+            "libcxx_guard",
+            "test_suite_guard",
+            "unimplemented",
+        ]
+        for key in tc.keys()
+    )
+    for tc in feature_test_macros
+)
 
 # Map from each header to the Lit annotations that should be used for
 # tests that include that header.
@@ -800,27 +1052,29 @@
 # <thread> should be marked as UNSUPPORTED, because including <thread>
 # is a hard error in that case.
 lit_markup = {
-  "barrier": ["UNSUPPORTED: no-threads"],
-  "filesystem": ["UNSUPPORTED: no-filesystem"],
-  "format": ["UNSUPPORTED: libcpp-has-no-incomplete-format"],
-  "iomanip": ["UNSUPPORTED: no-localization"],
-  "ios": ["UNSUPPORTED: no-localization"],
-  "iostream": ["UNSUPPORTED: no-localization"],
-  "istream": ["UNSUPPORTED: no-localization"],
-  "latch": ["UNSUPPORTED: no-threads"],
-  "locale": ["UNSUPPORTED: no-localization"],
-  "mutex": ["UNSUPPORTED: no-threads"],
-  "ostream": ["UNSUPPORTED: no-localization"],
-  "regex": ["UNSUPPORTED: no-localization"],
-  "semaphore": ["UNSUPPORTED: no-threads"],
-  "shared_mutex": ["UNSUPPORTED: no-threads"],
-  "stdatomic.h": ["UNSUPPORTED: no-threads"],
-  "thread": ["UNSUPPORTED: no-threads"],
+    "barrier": ["UNSUPPORTED: no-threads"],
+    "filesystem": ["UNSUPPORTED: no-filesystem"],
+    "format": ["UNSUPPORTED: libcpp-has-no-incomplete-format"],
+    "iomanip": ["UNSUPPORTED: no-localization"],
+    "ios": ["UNSUPPORTED: no-localization"],
+    "iostream": ["UNSUPPORTED: no-localization"],
+    "istream": ["UNSUPPORTED: no-localization"],
+    "latch": ["UNSUPPORTED: no-threads"],
+    "locale": ["UNSUPPORTED: no-localization"],
+    "mutex": ["UNSUPPORTED: no-threads"],
+    "ostream": ["UNSUPPORTED: no-localization"],
+    "regex": ["UNSUPPORTED: no-localization"],
+    "semaphore": ["UNSUPPORTED: no-threads"],
+    "shared_mutex": ["UNSUPPORTED: no-threads"],
+    "stdatomic.h": ["UNSUPPORTED: no-threads"],
+    "thread": ["UNSUPPORTED: no-threads"],
 }
 
+
 def get_std_dialects():
-  std_dialects = ['c++14', 'c++17', 'c++20', 'c++2b']
-  return list(std_dialects)
+    std_dialects = ["c++14", "c++17", "c++20", "c++2b"]
+    return list(std_dialects)
+
 
 def get_first_std(d):
     for s in get_std_dialects():
@@ -828,128 +1082,147 @@
             return s
     return None
 
+
 def get_last_std(d):
-  rev_dialects = get_std_dialects()
-  rev_dialects.reverse()
-  for s in rev_dialects:
-    if s in d.keys():
-      return s
-  return None
+    rev_dialects = get_std_dialects()
+    rev_dialects.reverse()
+    for s in rev_dialects:
+        if s in d.keys():
+            return s
+    return None
+
 
 def get_std_before(d, std):
-  std_dialects = get_std_dialects()
-  candidates = std_dialects[0:std_dialects.index(std)]
-  candidates.reverse()
-  for cand in candidates:
-    if cand in d.keys():
-      return cand
-  return None
+    std_dialects = get_std_dialects()
+    candidates = std_dialects[0 : std_dialects.index(std)]
+    candidates.reverse()
+    for cand in candidates:
+        if cand in d.keys():
+            return cand
+    return None
+
 
 def get_value_before(d, std):
-  new_std = get_std_before(d, std)
-  if new_std is None:
-    return None
-  return d[new_std]
+    new_std = get_std_before(d, std)
+    if new_std is None:
+        return None
+    return d[new_std]
+
 
 def get_for_std(d, std):
-  # This catches the C++11 case for which there should be no defined feature
-  # test macros.
-  std_dialects = get_std_dialects()
-  if std not in std_dialects:
+    # This catches the C++11 case for which there should be no defined feature
+    # test macros.
+    std_dialects = get_std_dialects()
+    if std not in std_dialects:
+        return None
+    # Find the value for the newest C++ dialect between C++14 and std
+    std_list = list(std_dialects[0 : std_dialects.index(std) + 1])
+    std_list.reverse()
+    for s in std_list:
+        if s in d.keys():
+            return d[s]
     return None
-  # Find the value for the newest C++ dialect between C++14 and std
-  std_list = list(std_dialects[0:std_dialects.index(std)+1])
-  std_list.reverse()
-  for s in std_list:
-    if s in d.keys():
-      return d[s]
-  return None
+
 
 def get_std_number(std):
-    return std.replace('c++', '')
+    return std.replace("c++", "")
+
 
 """
   Functions to produce the <version> header
 """
 
+
 def produce_macros_definition_for_std(std):
-  result = ""
-  indent = 55
-  for tc in feature_test_macros:
-    if std not in tc["values"]:
-      continue
-    inner_indent = 1
-    if 'test_suite_guard' in tc.keys():
-      result += "# if %s\n" % tc["libcxx_guard"]
-      inner_indent += 2
-    if get_value_before(tc["values"], std) is not None:
-      assert 'test_suite_guard' not in tc.keys()
-      result += "# undef  %s\n" % tc["name"]
-    line = "#%sdefine %s" % ((" " * inner_indent), tc["name"])
-    line += " " * (indent - len(line))
-    line += " %sL" % tc["values"][std]
-    if 'unimplemented' in tc.keys():
-      line = "// " + line
-    result += line
-    result += "\n"
-    if 'test_suite_guard' in tc.keys():
-      result += "# endif\n"
-  return result.strip()
+    result = ""
+    indent = 55
+    for tc in feature_test_macros:
+        if std not in tc["values"]:
+            continue
+        inner_indent = 1
+        if "test_suite_guard" in tc.keys():
+            result += "# if %s\n" % tc["libcxx_guard"]
+            inner_indent += 2
+        if get_value_before(tc["values"], std) is not None:
+            assert "test_suite_guard" not in tc.keys()
+            result += "# undef  %s\n" % tc["name"]
+        line = "#%sdefine %s" % ((" " * inner_indent), tc["name"])
+        line += " " * (indent - len(line))
+        line += " %sL" % tc["values"][std]
+        if "unimplemented" in tc.keys():
+            line = "// " + line
+        result += line
+        result += "\n"
+        if "test_suite_guard" in tc.keys():
+            result += "# endif\n"
+    return result.strip()
+
 
 def produce_macros_definitions():
-  macro_definition_template = """#if _LIBCPP_STD_VER >= {std_number}
+    macro_definition_template = """#if _LIBCPP_STD_VER >= {std_number}
 {macro_definition}
 #endif"""
 
-  macros_definitions = []
-  for std in get_std_dialects():
-    macros_definitions.append(
-      macro_definition_template.format(std_number=get_std_number(std).replace('2b', '23'),
-                                       macro_definition=produce_macros_definition_for_std(std)))
+    macros_definitions = []
+    for std in get_std_dialects():
+        macros_definitions.append(
+            macro_definition_template.format(
+                std_number=get_std_number(std).replace("2b", "23"),
+                macro_definition=produce_macros_definition_for_std(std),
+            )
+        )
+
+    return "\n\n".join(macros_definitions)
 
-  return '\n\n'.join(macros_definitions)
 
 def chunks(l, n):
-  """Yield successive n-sized chunks from l."""
-  for i in range(0, len(l), n):
-    yield l[i:i + n]
+    """Yield successive n-sized chunks from l."""
+    for i in range(0, len(l), n):
+        yield l[i : i + n]
+
 
 def produce_version_synopsis():
-  indent = 56
-  header_indent = 56 + len("20XXYYL ")
-  result = ""
-  def indent_to(s, val):
-    if len(s) >= val:
-      return s
-    s += " " * (val - len(s))
-    return s
-  line = indent_to("Macro name", indent) + "Value"
-  line = indent_to(line, header_indent) + "Headers"
-  result += line + "\n"
-  for tc in feature_test_macros:
-    prev_defined_std = get_last_std(tc["values"])
-    line = "{name: <{indent}}{value}L ".format(name=tc['name'], indent=indent,
-                                               value=tc["values"][prev_defined_std])
-    headers = list(tc["headers"])
-    headers.remove("version")
-    for chunk in chunks(headers, 3):
-      line = indent_to(line, header_indent)
-      chunk = ['<%s>' % header for header in chunk]
-      line += ' '.join(chunk)
-      result += line
-      result += "\n"
-      line = ""
-    while True:
-      prev_defined_std = get_std_before(tc["values"], prev_defined_std)
-      if prev_defined_std is None:
-        break
-      result += "%s%sL // %s\n" % (indent_to("", indent), tc["values"][prev_defined_std],
-                                prev_defined_std.replace("c++", "C++"))
-  return result
+    indent = 56
+    header_indent = 56 + len("20XXYYL ")
+    result = ""
+
+    def indent_to(s, val):
+        if len(s) >= val:
+            return s
+        s += " " * (val - len(s))
+        return s
+
+    line = indent_to("Macro name", indent) + "Value"
+    line = indent_to(line, header_indent) + "Headers"
+    result += line + "\n"
+    for tc in feature_test_macros:
+        prev_defined_std = get_last_std(tc["values"])
+        line = "{name: <{indent}}{value}L ".format(
+            name=tc["name"], indent=indent, value=tc["values"][prev_defined_std]
+        )
+        headers = list(tc["headers"])
+        headers.remove("version")
+        for chunk in chunks(headers, 3):
+            line = indent_to(line, header_indent)
+            chunk = ["<%s>" % header for header in chunk]
+            line += " ".join(chunk)
+            result += line
+            result += "\n"
+            line = ""
+        while True:
+            prev_defined_std = get_std_before(tc["values"], prev_defined_std)
+            if prev_defined_std is None:
+                break
+            result += "%s%sL // %s\n" % (
+                indent_to("", indent),
+                tc["values"][prev_defined_std],
+                prev_defined_std.replace("c++", "C++"),
+            )
+    return result
 
 
 def produce_version_header():
-  template="""// -*- C++ -*-
+    template = """// -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -984,12 +1257,13 @@
 #endif // _LIBCPP_VERSIONH
 """
 
-  version_str = template.format(
-      synopsis=produce_version_synopsis().strip(),
-      cxx_macros=produce_macros_definitions())
-  version_header_path = os.path.join(include_path, 'version')
-  with open(version_header_path, 'w', newline='\n') as f:
-    f.write(version_str)
+    version_str = template.format(
+        synopsis=produce_version_synopsis().strip(),
+        cxx_macros=produce_macros_definitions(),
+    )
+    version_header_path = os.path.join(include_path, "version")
+    with open(version_header_path, "w", newline="\n") as f:
+        f.write(version_str)
 
 
 """
@@ -997,13 +1271,12 @@
 """
 
 test_types = {
-  "undefined": """
+    "undefined": """
 # ifdef {name}
 #   error "{name} should not be defined before {std_first}"
 # endif
 """,
-
-  "test_suite_guard": """
+    "test_suite_guard": """
 # if {test_suite_guard}
 #   ifndef {name}
 #     error "{name} should be defined in {std}"
@@ -1017,8 +1290,7 @@
 #   endif
 # endif
 """,
-
-  "unimplemented": """
+    "unimplemented": """
 # if !defined(_LIBCPP_VERSION)
 #   ifndef {name}
 #     error "{name} should be defined in {std}"
@@ -1032,35 +1304,45 @@
 #   endif
 # endif
 """,
-
-  "defined": """
+    "defined": """
 # ifndef {name}
 #   error "{name} should be defined in {std}"
 # endif
 # if {name} != {value}
 #   error "{name} should have the value {value} in {std}"
 # endif
-"""
+""",
 }
 
+
 def generate_std_test(test_list, std):
-  result = ""
-  for tc in test_list:
-    val = get_for_std(tc["values"], std)
-    if val is not None:
-      val = "%sL" % val
-    if val is None:
-      result += test_types["undefined"].format(name=tc["name"], std_first=get_first_std(tc["values"]))
-    elif 'unimplemented' in tc.keys():
-      result += test_types["unimplemented"].format(name=tc["name"], value=val, std=std)
-    elif "test_suite_guard" in tc.keys():
-      result += test_types["test_suite_guard"].format(name=tc["name"], value=val, std=std, test_suite_guard=tc["test_suite_guard"])
-    else:
-      result +=  test_types["defined"].format(name=tc["name"], value=val, std=std)
-  return result.strip()
+    result = ""
+    for tc in test_list:
+        val = get_for_std(tc["values"], std)
+        if val is not None:
+            val = "%sL" % val
+        if val is None:
+            result += test_types["undefined"].format(
+                name=tc["name"], std_first=get_first_std(tc["values"])
+            )
+        elif "unimplemented" in tc.keys():
+            result += test_types["unimplemented"].format(
+                name=tc["name"], value=val, std=std
+            )
+        elif "test_suite_guard" in tc.keys():
+            result += test_types["test_suite_guard"].format(
+                name=tc["name"],
+                value=val,
+                std=std,
+                test_suite_guard=tc["test_suite_guard"],
+            )
+        else:
+            result += test_types["defined"].format(name=tc["name"], value=val, std=std)
+    return result.strip()
+
 
 def generate_std_tests(test_list):
-  std_tests_template = """#if TEST_STD_VER < {first_std_number}
+    std_tests_template = """#if TEST_STD_VER < {first_std_number}
 
 {pre_std_test}
 
@@ -1072,49 +1354,57 @@
 
 #endif // TEST_STD_VER > {penultimate_std_number}"""
 
-  std_dialects = get_std_dialects()
-  assert not get_std_number(std_dialects[-1]).isnumeric()
+    std_dialects = get_std_dialects()
+    assert not get_std_number(std_dialects[-1]).isnumeric()
 
-  other_std_tests = []
-  for std in std_dialects[:-1]:
-    other_std_tests.append('#elif TEST_STD_VER == ' + get_std_number(std))
-    other_std_tests.append(generate_std_test(test_list, std))
+    other_std_tests = []
+    for std in std_dialects[:-1]:
+        other_std_tests.append("#elif TEST_STD_VER == " + get_std_number(std))
+        other_std_tests.append(generate_std_test(test_list, std))
 
-  std_tests = std_tests_template.format(first_std_number=get_std_number(std_dialects[0]),
-                                        pre_std_test=generate_std_test(test_list, 'c++11'),
-                                        other_std_tests='\n\n'.join(other_std_tests),
-                                        penultimate_std_number=get_std_number(std_dialects[-2]),
-                                        last_std_test=generate_std_test(test_list, std_dialects[-1]))
+    std_tests = std_tests_template.format(
+        first_std_number=get_std_number(std_dialects[0]),
+        pre_std_test=generate_std_test(test_list, "c++11"),
+        other_std_tests="\n\n".join(other_std_tests),
+        penultimate_std_number=get_std_number(std_dialects[-2]),
+        last_std_test=generate_std_test(test_list, std_dialects[-1]),
+    )
+
+    return std_tests
 
-  return std_tests
 
 def generate_synopsis(test_list):
     max_name_len = max([len(tc["name"]) for tc in test_list])
     indent = max_name_len + 8
+
     def mk_line(prefix, suffix):
-        return "{prefix: <{max_len}}{suffix}\n".format(prefix=prefix, suffix=suffix,
-        max_len=indent)
+        return "{prefix: <{max_len}}{suffix}\n".format(
+            prefix=prefix, suffix=suffix, max_len=indent
+        )
+
     result = ""
     result += mk_line("/*  Constant", "Value")
     for tc in test_list:
         prefix = "    %s" % tc["name"]
         for std in [s for s in get_std_dialects() if s in tc["values"].keys()]:
-            result += mk_line(prefix, "%sL [%s]" % (tc["values"][std], std.replace("c++", "C++")))
+            result += mk_line(
+                prefix, "%sL [%s]" % (tc["values"][std], std.replace("c++", "C++"))
+            )
             prefix = ""
     result += "*/"
     return result
 
+
 def produce_tests():
-  headers = set([h for tc in feature_test_macros for h in tc["headers"]])
-  for h in headers:
-    test_list = [tc for tc in feature_test_macros if h in tc["headers"]]
-    if not has_header(h):
-      for tc in test_list:
-        assert 'unimplemented' in tc.keys()
-      continue
-    markup = '\n'.join('// ' + tag for tag in lit_markup.get(h, []))
-    test_body = \
-"""//===----------------------------------------------------------------------===//
+    headers = set([h for tc in feature_test_macros for h in tc["headers"]])
+    for h in headers:
+        test_list = [tc for tc in feature_test_macros if h in tc["headers"]]
+        if not has_header(h):
+            for tc in test_list:
+                assert "unimplemented" in tc.keys()
+            continue
+        markup = "\n".join("// " + tag for tag in lit_markup.get(h, []))
+        test_body = """//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -1138,72 +1428,86 @@
 
 {cxx_tests}
 
-""".format(script_name=script_name,
-           header=h,
-           markup=('\n{}\n'.format(markup) if markup else ''),
-           synopsis=generate_synopsis(test_list),
-           cxx_tests=generate_std_tests(test_list))
-    test_name = "{header}.version.compile.pass.cpp".format(header=h)
-    out_path = os.path.join(macro_test_path, test_name)
-    with open(out_path, 'w', newline='\n') as f:
-      f.write(test_body)
+""".format(
+            script_name=script_name,
+            header=h,
+            markup=("\n{}\n".format(markup) if markup else ""),
+            synopsis=generate_synopsis(test_list),
+            cxx_tests=generate_std_tests(test_list),
+        )
+        test_name = "{header}.version.compile.pass.cpp".format(header=h)
+        out_path = os.path.join(macro_test_path, test_name)
+        with open(out_path, "w", newline="\n") as f:
+            f.write(test_body)
+
 
 """
     Produce documentation for the feature test macros
 """
 
+
 def make_widths(grid):
-  widths = []
-  for i in range(0, len(grid[0])):
-    cell_width = 2 + max(reduce(lambda x,y: x+y, [[len(row[i])] for row in grid], []))
-    widths += [cell_width]
-  return widths
+    widths = []
+    for i in range(0, len(grid[0])):
+        cell_width = 2 + max(
+            reduce(lambda x, y: x + y, [[len(row[i])] for row in grid], [])
+        )
+        widths += [cell_width]
+    return widths
+
 
 def create_table(grid, indent):
-  indent_str = ' '*indent
-  col_widths = make_widths(grid)
-  result = [indent_str + add_divider(col_widths, 2)]
-  header_flag = 2
-  for row_i in range(0, len(grid)):
-    row = grid[row_i]
-    line = indent_str + ' '.join([pad_cell(row[i], col_widths[i]) for i in range(0, len(row))])
-    result.append(line.rstrip())
-    is_cxx_header = row[0].startswith('**')
-    if row_i == len(grid) - 1:
-      header_flag = 2
-    separator = indent_str + add_divider(col_widths, 1 if is_cxx_header else header_flag)
-    result.append(separator.rstrip())
-    header_flag = 0
-  return '\n'.join(result)
+    indent_str = " " * indent
+    col_widths = make_widths(grid)
+    result = [indent_str + add_divider(col_widths, 2)]
+    header_flag = 2
+    for row_i in range(0, len(grid)):
+        row = grid[row_i]
+        line = indent_str + " ".join(
+            [pad_cell(row[i], col_widths[i]) for i in range(0, len(row))]
+        )
+        result.append(line.rstrip())
+        is_cxx_header = row[0].startswith("**")
+        if row_i == len(grid) - 1:
+            header_flag = 2
+        separator = indent_str + add_divider(
+            col_widths, 1 if is_cxx_header else header_flag
+        )
+        result.append(separator.rstrip())
+        header_flag = 0
+    return "\n".join(result)
+
 
 def add_divider(widths, header_flag):
-  if header_flag == 2:
-    return ' '.join(['='*w for w in widths])
-  if header_flag == 1:
-    return '-'.join(['-'*w for w in widths])
-  else:
-    return ' '.join(['-'*w for w in widths])
+    if header_flag == 2:
+        return " ".join(["=" * w for w in widths])
+    if header_flag == 1:
+        return "-".join(["-" * w for w in widths])
+    else:
+        return " ".join(["-" * w for w in widths])
+
 
 def pad_cell(s, length, left_align=True):
-  padding = ((length - len(s)) * ' ')
-  return s + padding
+    padding = (length - len(s)) * " "
+    return s + padding
 
 
 def get_status_table():
-  table = [["Macro Name", "Value"]]
-  for std in get_std_dialects():
-    table += [["**" + std.replace("c++", "C++ ") + "**", ""]]
-    for tc in feature_test_macros:
-      if std not in tc["values"].keys():
-        continue
-      value = "``%sL``" % tc["values"][std]
-      if 'unimplemented' in tc.keys():
-        value = '*unimplemented*'
-      table += [["``%s``" % tc["name"], value]]
-  return table
+    table = [["Macro Name", "Value"]]
+    for std in get_std_dialects():
+        table += [["**" + std.replace("c++", "C++ ") + "**", ""]]
+        for tc in feature_test_macros:
+            if std not in tc["values"].keys():
+                continue
+            value = "``%sL``" % tc["values"][std]
+            if "unimplemented" in tc.keys():
+                value = "*unimplemented*"
+            table += [["``%s``" % tc["name"], value]]
+    return table
+
 
 def produce_docs():
-  doc_str = """.. _FeatureTestMacroTable:
+    doc_str = """.. _FeatureTestMacroTable:
 
 ==========================
 Feature Test Macro Support
@@ -1228,17 +1532,20 @@
 
 {status_tables}
 
-""".format(status_tables=create_table(get_status_table(), 4))
+""".format(
+        status_tables=create_table(get_status_table(), 4)
+    )
+
+    table_doc_path = os.path.join(docs_path, "FeatureTestMacroTable.rst")
+    with open(table_doc_path, "w", newline="\n") as f:
+        f.write(doc_str)
 
-  table_doc_path = os.path.join(docs_path, 'FeatureTestMacroTable.rst')
-  with open(table_doc_path, 'w', newline='\n') as f:
-    f.write(doc_str)
 
 def main():
-  produce_version_header()
-  produce_tests()
-  produce_docs()
+    produce_version_header()
+    produce_tests()
+    produce_docs()
 
 
-if __name__ == '__main__':
-  main()
+if __name__ == "__main__":
+    main()
diff --git a/libcxx/utils/generate_header_inclusion_tests.py b/libcxx/utils/generate_header_inclusion_tests.py
--- a/libcxx/utils/generate_header_inclusion_tests.py
+++ b/libcxx/utils/generate_header_inclusion_tests.py
@@ -8,9 +8,11 @@
     script_name = os.path.basename(__file__)
     assert os.path.exists(utils_path)
     src_root = os.path.dirname(utils_path)
-    test_path = os.path.join(src_root, 'test', 'libcxx', 'inclusions')
+    test_path = os.path.join(src_root, "test", "libcxx", "inclusions")
     assert os.path.exists(test_path)
-    assert os.path.exists(os.path.join(test_path, 'algorithm.inclusions.compile.pass.cpp'))
+    assert os.path.exists(
+        os.path.join(test_path, "algorithm.inclusions.compile.pass.cpp")
+    )
     return script_name, src_root, test_path
 
 
@@ -93,46 +95,46 @@
 # <thread> should be marked as UNSUPPORTED, because including <thread>
 # is a hard error in that case.
 lit_markup = {
-  "barrier": ["UNSUPPORTED: no-threads"],
-  "filesystem": ["UNSUPPORTED: no-filesystem"],
-  "format": ["UNSUPPORTED: libcpp-has-no-incomplete-format"],
-  "iomanip": ["UNSUPPORTED: no-localization"],
-  "ios": ["UNSUPPORTED: no-localization"],
-  "iostream": ["UNSUPPORTED: no-localization"],
-  "istream": ["UNSUPPORTED: no-localization"],
-  "latch": ["UNSUPPORTED: no-threads"],
-  "locale": ["UNSUPPORTED: no-localization"],
-  "mutex": ["UNSUPPORTED: no-threads"],
-  "ostream": ["UNSUPPORTED: no-localization"],
-  "regex": ["UNSUPPORTED: no-localization"],
-  "semaphore": ["UNSUPPORTED: no-threads"],
-  "shared_mutex": ["UNSUPPORTED: no-threads"],
-  "thread": ["UNSUPPORTED: no-threads"]
+    "barrier": ["UNSUPPORTED: no-threads"],
+    "filesystem": ["UNSUPPORTED: no-filesystem"],
+    "format": ["UNSUPPORTED: libcpp-has-no-incomplete-format"],
+    "iomanip": ["UNSUPPORTED: no-localization"],
+    "ios": ["UNSUPPORTED: no-localization"],
+    "iostream": ["UNSUPPORTED: no-localization"],
+    "istream": ["UNSUPPORTED: no-localization"],
+    "latch": ["UNSUPPORTED: no-threads"],
+    "locale": ["UNSUPPORTED: no-localization"],
+    "mutex": ["UNSUPPORTED: no-threads"],
+    "ostream": ["UNSUPPORTED: no-localization"],
+    "regex": ["UNSUPPORTED: no-localization"],
+    "semaphore": ["UNSUPPORTED: no-threads"],
+    "shared_mutex": ["UNSUPPORTED: no-threads"],
+    "thread": ["UNSUPPORTED: no-threads"],
 }
 
 
 def get_std_ver_test(includee):
     v = new_in_version.get(includee, "03")
     if v == "03":
-        return ''
+        return ""
     versions = ["03", "11", "14", "17", "20"]
-    return 'TEST_STD_VER > {} && '.format(max(i for i in versions if i < v))
+    return "TEST_STD_VER > {} && ".format(max(i for i in versions if i < v))
 
 
 def get_unsupported_line(includee):
     v = new_in_version.get(includee, "03")
     return {
         "03": [],
-        "11": ['UNSUPPORTED: c++03'],
-        "14": ['UNSUPPORTED: c++03, c++11'],
-        "17": ['UNSUPPORTED: c++03, c++11, c++14'],
-        "20": ['UNSUPPORTED: c++03, c++11, c++14, c++17'],
-        "2b": ['UNSUPPORTED: c++03, c++11, c++14, c++17, c++20'],
+        "11": ["UNSUPPORTED: c++03"],
+        "14": ["UNSUPPORTED: c++03, c++11"],
+        "17": ["UNSUPPORTED: c++03, c++11, c++14"],
+        "20": ["UNSUPPORTED: c++03, c++11, c++14, c++17"],
+        "2b": ["UNSUPPORTED: c++03, c++11, c++14, c++17, c++20"],
     }[v]
 
 
 def get_libcpp_header_symbol(header_name):
-    return '_LIBCPP_' + header_name.upper().replace('.', '_')
+    return "_LIBCPP_" + header_name.upper().replace(".", "_")
 
 
 def get_includer_symbol_test(includer):
@@ -157,7 +159,9 @@
     """.strip().format(
         includee_test=get_std_ver_test(includee),
         symbol=symbol,
-        message="<{}> should include <{}> in C++{} and later".format(includer, includee, version)
+        message="<{}> should include <{}> in C++{} and later".format(
+            includer, includee, version
+        ),
     )
 
 
@@ -193,15 +197,19 @@
         test_body = test_body_template.format(
             script_name=script_name,
             header=includer,
-            markup=('\n' + '\n'.join('// ' + m for m in markup_tags) + '\n') if markup_tags else '',
+            markup=("\n" + "\n".join("// " + m for m in markup_tags) + "\n")
+            if markup_tags
+            else "",
             test_includers_symbol=get_includer_symbol_test(includer),
-            test_per_includee='\n'.join(get_ifdef(includer, includee) for includee in includees),
+            test_per_includee="\n".join(
+                get_ifdef(includer, includee) for includee in includees
+            ),
         )
         test_name = "{header}.inclusions.compile.pass.cpp".format(header=includer)
         out_path = os.path.join(test_path, test_name)
-        with open(out_path, 'w', newline='\n') as f:
-            f.write(test_body + '\n')
+        with open(out_path, "w", newline="\n") as f:
+            f.write(test_body + "\n")
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     produce_tests()
diff --git a/libcxx/utils/generate_header_tests.py b/libcxx/utils/generate_header_tests.py
--- a/libcxx/utils/generate_header_tests.py
+++ b/libcxx/utils/generate_header_tests.py
@@ -16,12 +16,9 @@
     "shared_mutex": "!defined(_LIBCPP_HAS_NO_THREADS)",
     "stdatomic.h": "__cplusplus > 202002L && !defined(_LIBCPP_HAS_NO_THREADS)",
     "thread": "!defined(_LIBCPP_HAS_NO_THREADS)",
-
     "filesystem": "!defined(_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY)",
-
     # TODO LLVM17: simplify this to __cplusplus >= 202002L
     "coroutine": "(defined(__cpp_impl_coroutine) && __cpp_impl_coroutine >= 201902L) || (defined(__cpp_coroutines) && __cpp_coroutines >= 201703L)",
-
     "clocale": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
     "codecvt": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
     "fstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION) && !defined(_LIBCPP_HAS_NO_FSTREAM)",
@@ -36,12 +33,10 @@
     "sstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
     "streambuf": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
     "strstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
-
     "wctype.h": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
     "cwctype": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
     "cwchar": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
     "wchar.h": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
-
     "experimental/algorithm": "__cplusplus >= 201103L",
     "experimental/deque": "__cplusplus >= 201103L",
     "experimental/forward_list": "__cplusplus >= 201103L",
@@ -64,89 +59,133 @@
 }
 
 private_headers_still_public_in_modules = [
-    '__assert', '__config',
-    '__config_site.in', '__debug', '__hash_table',
-    '__threading_support', '__tree', '__undef_macros', '__verbose_abort'
+    "__assert",
+    "__config",
+    "__config_site.in",
+    "__debug",
+    "__hash_table",
+    "__threading_support",
+    "__tree",
+    "__undef_macros",
+    "__verbose_abort",
 ]
 
+
 def find_script(file):
     """Finds the script used to generate a file inside the file itself. The script is delimited by
-       BEGIN-SCRIPT and END-SCRIPT markers.
+    BEGIN-SCRIPT and END-SCRIPT markers.
     """
-    with open(file, 'r') as f:
+    with open(file, "r") as f:
         content = f.read()
 
-    match = re.search(r'^BEGIN-SCRIPT$(.+)^END-SCRIPT$', content, flags=re.MULTILINE | re.DOTALL)
+    match = re.search(
+        r"^BEGIN-SCRIPT$(.+)^END-SCRIPT$", content, flags=re.MULTILINE | re.DOTALL
+    )
     if not match:
-        raise RuntimeError("Was unable to find a script delimited with BEGIN-SCRIPT/END-SCRIPT markers in {}".format(test_file))
+        raise RuntimeError(
+            "Was unable to find a script delimited with BEGIN-SCRIPT/END-SCRIPT markers in {}".format(
+                test_file
+            )
+        )
     return match.group(1)
 
+
 def execute_script(script, variables):
     """Executes the provided Mako template with the given variables available during the
-       evaluation of the script, and returns the result.
+    evaluation of the script, and returns the result.
     """
-    code = compile(script, 'fake-filename', 'exec')
+    code = compile(script, "fake-filename", "exec")
     output = io.StringIO()
     with contextlib.redirect_stdout(output):
         exec(code, variables)
         output = output.getvalue()
     return output
 
+
 def generate_new_file(file, new_content):
     """Generates the new content of the file by inserting the new content in-between
-       two '// GENERATED-MARKER' markers located in the file.
+    two '// GENERATED-MARKER' markers located in the file.
     """
-    with open(file, 'r') as f:
+    with open(file, "r") as f:
         old_content = f.read()
 
     try:
-        before, begin_marker, _, end_marker, after = re.split(r'(// GENERATED-MARKER\n)', old_content, flags=re.MULTILINE | re.DOTALL)
+        before, begin_marker, _, end_marker, after = re.split(
+            r"(// GENERATED-MARKER\n)", old_content, flags=re.MULTILINE | re.DOTALL
+        )
     except ValueError:
-        raise RuntimeError("Failed to split {} based on markers, please make sure the file has exactly two '// GENERATED-MARKER' occurrences".format(file))
+        raise RuntimeError(
+            "Failed to split {} based on markers, please make sure the file has exactly two '// GENERATED-MARKER' occurrences".format(
+                file
+            )
+        )
 
     return before + begin_marker + new_content + end_marker + after
 
+
 def produce(test_file, variables):
     script = find_script(test_file)
     result = execute_script(script, variables)
     new_content = generate_new_file(test_file, result)
-    with open(test_file, 'w', newline='\n') as f:
+    with open(test_file, "w", newline="\n") as f:
         f.write(new_content)
 
+
 def is_header(file):
     """Returns whether the given file is a header (i.e. not a directory or the modulemap file)."""
-    return not file.is_dir() and not file.name == 'module.modulemap.in' and file.name != 'libcxx.imp'
+    return (
+        not file.is_dir()
+        and not file.name == "module.modulemap.in"
+        and file.name != "libcxx.imp"
+    )
 
 
 def main():
-    monorepo_root = pathlib.Path(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))))
-    include = pathlib.Path(os.path.join(monorepo_root, 'libcxx', 'include'))
-    test = pathlib.Path(os.path.join(monorepo_root, 'libcxx', 'test'))
-    assert(monorepo_root.exists())
-
-    toplevel_headers     = sorted(str(p.relative_to(include)) for p in include.glob('[a-z]*') if is_header(p))
-    experimental_headers = sorted(str(p.relative_to(include)) for p in include.glob('experimental/[a-z]*') if is_header(p))
-    public_headers       = toplevel_headers + experimental_headers
-    private_headers      = sorted(str(p.relative_to(include)) for p in include.rglob('*') if is_header(p) and str(p.relative_to(include)).startswith('__') and not p.name.startswith('pstl'))
+    monorepo_root = pathlib.Path(
+        os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+    )
+    include = pathlib.Path(os.path.join(monorepo_root, "libcxx", "include"))
+    test = pathlib.Path(os.path.join(monorepo_root, "libcxx", "test"))
+    assert monorepo_root.exists()
+
+    toplevel_headers = sorted(
+        str(p.relative_to(include)) for p in include.glob("[a-z]*") if is_header(p)
+    )
+    experimental_headers = sorted(
+        str(p.relative_to(include))
+        for p in include.glob("experimental/[a-z]*")
+        if is_header(p)
+    )
+    public_headers = toplevel_headers + experimental_headers
+    private_headers = sorted(
+        str(p.relative_to(include))
+        for p in include.rglob("*")
+        if is_header(p)
+        and str(p.relative_to(include)).startswith("__")
+        and not p.name.startswith("pstl")
+    )
     variables = {
-        'toplevel_headers': toplevel_headers,
-        'experimental_headers': experimental_headers,
-        'public_headers': public_headers,
-        'private_headers': private_headers,
-        'header_restrictions': header_restrictions,
-        'private_headers_still_public_in_modules': private_headers_still_public_in_modules
+        "toplevel_headers": toplevel_headers,
+        "experimental_headers": experimental_headers,
+        "public_headers": public_headers,
+        "private_headers": private_headers,
+        "header_restrictions": header_restrictions,
+        "private_headers_still_public_in_modules": private_headers_still_public_in_modules,
     }
 
-    produce(test.joinpath('libcxx/assertions/headers_declare_verbose_abort.sh.cpp'), variables)
-    produce(test.joinpath('libcxx/clang_tidy.sh.cpp'), variables)
-    produce(test.joinpath('libcxx/double_include.sh.cpp'), variables)
-    produce(test.joinpath('libcxx/min_max_macros.compile.pass.cpp'), variables)
-    produce(test.joinpath('libcxx/modules_include.sh.cpp'), variables)
-    produce(test.joinpath('libcxx/nasty_macros.compile.pass.cpp'), variables)
-    produce(test.joinpath('libcxx/no_assert_include.compile.pass.cpp'), variables)
-    produce(test.joinpath('libcxx/private_headers.verify.cpp'), variables)
-    produce(test.joinpath('libcxx/transitive_includes.sh.cpp'), variables)
-
-
-if __name__ == '__main__':
+    produce(
+        test.joinpath("libcxx/assertions/headers_declare_verbose_abort.sh.cpp"),
+        variables,
+    )
+    produce(test.joinpath("libcxx/clang_tidy.sh.cpp"), variables)
+    produce(test.joinpath("libcxx/double_include.sh.cpp"), variables)
+    produce(test.joinpath("libcxx/min_max_macros.compile.pass.cpp"), variables)
+    produce(test.joinpath("libcxx/modules_include.sh.cpp"), variables)
+    produce(test.joinpath("libcxx/nasty_macros.compile.pass.cpp"), variables)
+    produce(test.joinpath("libcxx/no_assert_include.compile.pass.cpp"), variables)
+    produce(test.joinpath("libcxx/private_headers.verify.cpp"), variables)
+    produce(test.joinpath("libcxx/transitive_includes.sh.cpp"), variables)
+
+
+if __name__ == "__main__":
     main()
diff --git a/libcxx/utils/generate_iwyu_mapping.py b/libcxx/utils/generate_iwyu_mapping.py
--- a/libcxx/utils/generate_iwyu_mapping.py
+++ b/libcxx/utils/generate_iwyu_mapping.py
@@ -2,13 +2,17 @@
 
 import os, pathlib, sys
 
+
 def generate(private, public):
     return f'{{ include: [ "{private}", "private", "<{public}>", "public" ] }}'
 
 
 def panic(file):
-    print(f'========== {__file__} error ==========', file=sys.stderr)
-    print(f'\tFile \'{file}\' is a top-level detail header without a mapping', file=sys.stderr)
+    print(f"========== {__file__} error ==========", file=sys.stderr)
+    print(
+        f"\tFile '{file}' is a top-level detail header without a mapping",
+        file=sys.stderr,
+    )
     sys.exit(1)
 
 
@@ -18,50 +22,75 @@
     c_headers = []
 
     for i in include.iterdir():
-        if i.is_dir() and i.name.startswith('__'):
-            detail_directories.append(f'{i.name}')
+        if i.is_dir() and i.name.startswith("__"):
+            detail_directories.append(f"{i.name}")
             continue
 
-        if i.name.startswith('__'):
+        if i.name.startswith("__"):
             detail_files.append(i.name)
             continue
 
-        if i.name.endswith('.h'):
+        if i.name.endswith(".h"):
             c_headers.append(i.name)
 
     result = []
-    temporary_mappings = {'__locale_dir' : 'locale'}
+    temporary_mappings = {"__locale_dir": "locale"}
     for i in detail_directories:
-        public_header = temporary_mappings.get(i, i.lstrip('_'))
+        public_header = temporary_mappings.get(i, i.lstrip("_"))
         result.append(f'{generate(f"@<{i}/.*>", public_header)},')
 
     for i in detail_files:
         public = []
-        if   i == '__assert': continue
-        elif i == '__availability': continue
-        elif i == '__bit_reference': continue
-        elif i == '__bits': public = ['bits']
-        elif i == '__config_site.in': continue
-        elif i == '__config': continue
-        elif i == '__debug': continue
-        elif i == '__errc': continue
-        elif i == '__hash_table': public = ['unordered_map', 'unordered_set']
-        elif i == '__locale': public = ['locale']
-        elif i == '__mbstate_t.h': continue
-        elif i == '__mutex_base': continue
-        elif i == '__node_handle': public = ['map', 'set', 'unordered_map', 'unordered_set']
-        elif i == '__pstl_algorithm': continue
-        elif i == '__pstl_config_site.in': continue
-        elif i == '__pstl_execution': continue
-        elif i == '__pstl_memory': continue
-        elif i == '__pstl_numeric': continue
-        elif i == '__split_buffer': public = ['deque', 'vector']
-        elif i == '__std_mbstate_t.h': continue
-        elif i == '__threading_support': public = ['atomic', 'mutex', 'semaphore', 'thread']
-        elif i == '__tree': public = ['map', 'set']
-        elif i == '__undef_macros': continue
-        elif i == '__verbose_abort': continue
-        else: panic(i)
+        if i == "__assert":
+            continue
+        elif i == "__availability":
+            continue
+        elif i == "__bit_reference":
+            continue
+        elif i == "__bits":
+            public = ["bits"]
+        elif i == "__config_site.in":
+            continue
+        elif i == "__config":
+            continue
+        elif i == "__debug":
+            continue
+        elif i == "__errc":
+            continue
+        elif i == "__hash_table":
+            public = ["unordered_map", "unordered_set"]
+        elif i == "__locale":
+            public = ["locale"]
+        elif i == "__mbstate_t.h":
+            continue
+        elif i == "__mutex_base":
+            continue
+        elif i == "__node_handle":
+            public = ["map", "set", "unordered_map", "unordered_set"]
+        elif i == "__pstl_algorithm":
+            continue
+        elif i == "__pstl_config_site.in":
+            continue
+        elif i == "__pstl_execution":
+            continue
+        elif i == "__pstl_memory":
+            continue
+        elif i == "__pstl_numeric":
+            continue
+        elif i == "__split_buffer":
+            public = ["deque", "vector"]
+        elif i == "__std_mbstate_t.h":
+            continue
+        elif i == "__threading_support":
+            public = ["atomic", "mutex", "semaphore", "thread"]
+        elif i == "__tree":
+            public = ["map", "set"]
+        elif i == "__undef_macros":
+            continue
+        elif i == "__verbose_abort":
+            continue
+        else:
+            panic(i)
 
         for p in public:
             result.append(f'{generate(f"<{i}>", p)},')
@@ -69,16 +98,19 @@
     result.sort()
     return result
 
+
 def main():
-    monorepo_root = pathlib.Path(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))))
-    assert(monorepo_root.exists())
-    include = pathlib.Path(os.path.join(monorepo_root, 'libcxx', 'include'))
+    monorepo_root = pathlib.Path(
+        os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+    )
+    assert monorepo_root.exists()
+    include = pathlib.Path(os.path.join(monorepo_root, "libcxx", "include"))
 
     mapping = generate_map(include)
-    data = '[\n  ' + '\n  '.join(mapping) + '\n]\n'
-    with open(f'{include}/libcxx.imp', 'w') as f:
+    data = "[\n  " + "\n  ".join(mapping) + "\n]\n"
+    with open(f"{include}/libcxx.imp", "w") as f:
         f.write(data)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     main()
diff --git a/libcxx/utils/generate_width_estimation_table.py b/libcxx/utils/generate_width_estimation_table.py
--- a/libcxx/utils/generate_width_estimation_table.py
+++ b/libcxx/utils/generate_width_estimation_table.py
@@ -326,10 +326,7 @@
     Generate Unicode data for [format.string.std]/12
     """
     east_asian_width_path = (
-        Path(__file__).absolute().parent
-        / "data"
-        / "unicode"
-        / "EastAsianWidth.txt"
+        Path(__file__).absolute().parent / "data" / "unicode" / "EastAsianWidth.txt"
     )
 
     properties = list()
diff --git a/libcxx/utils/libcxx/__init__.py b/libcxx/utils/libcxx/__init__.py
--- a/libcxx/utils/libcxx/__init__.py
+++ b/libcxx/utils/libcxx/__init__.py
@@ -1,16 +1,16 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 """libcxx python utilities"""
 
-__author__ = 'Eric Fiselier'
-__email__ = 'eric@efcs.ca'
+__author__ = "Eric Fiselier"
+__email__ = "eric@efcs.ca"
 __versioninfo__ = (0, 1, 0)
-__version__ = ' '.join(str(v) for v in __versioninfo__) + 'dev'
+__version__ = " ".join(str(v) for v in __versioninfo__) + "dev"
 
 __all__ = []
diff --git a/libcxx/utils/libcxx/sym_check/__init__.py b/libcxx/utils/libcxx/sym_check/__init__.py
--- a/libcxx/utils/libcxx/sym_check/__init__.py
+++ b/libcxx/utils/libcxx/sym_check/__init__.py
@@ -1,16 +1,16 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 """libcxx abi symbol checker"""
 
-__author__ = 'Eric Fiselier'
-__email__ = 'eric@efcs.ca'
+__author__ = "Eric Fiselier"
+__email__ = "eric@efcs.ca"
 __versioninfo__ = (0, 1, 0)
-__version__ = ' '.join(str(v) for v in __versioninfo__) + 'dev'
+__version__ = " ".join(str(v) for v in __versioninfo__) + "dev"
 
-__all__ = ['diff', 'extract', 'util']
+__all__ = ["diff", "extract", "util"]
diff --git a/libcxx/utils/libcxx/sym_check/diff.py b/libcxx/utils/libcxx/sym_check/diff.py
--- a/libcxx/utils/libcxx/sym_check/diff.py
+++ b/libcxx/utils/libcxx/sym_check/diff.py
@@ -1,11 +1,11 @@
 # -*- Python -*- vim: set syntax=python tabstop=4 expandtab cc=80:
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """
 diff - A set of functions for diff-ing two symbol lists.
 """
@@ -14,15 +14,15 @@
 
 
 def _symbol_difference(lhs, rhs):
-    lhs_names = set(((n['name'], n['type']) for n in lhs))
-    rhs_names = set(((n['name'], n['type']) for n in rhs))
+    lhs_names = set(((n["name"], n["type"]) for n in lhs))
+    rhs_names = set(((n["name"], n["type"]) for n in rhs))
     diff_names = lhs_names - rhs_names
-    return [n for n in lhs if (n['name'], n['type']) in diff_names]
+    return [n for n in lhs if (n["name"], n["type"]) in diff_names]
 
 
 def _find_by_key(sym_list, k):
     for sym in sym_list:
-        if sym['name'] == k:
+        if sym["name"] == k:
             return sym
     return None
 
@@ -40,9 +40,8 @@
     for old_sym in old:
         if old_sym in new:
             continue
-        new_sym = _find_by_key(new, old_sym['name'])
-        if (new_sym is not None and not new_sym in old
-                and old_sym != new_sym):
+        new_sym = _find_by_key(new, old_sym["name"])
+        if new_sym is not None and not new_sym in old and old_sym != new_sym:
             changed += [(old_sym, new_sym)]
     return changed
 
@@ -54,49 +53,51 @@
     return added, removed, changed
 
 
-def report_diff(added_syms, removed_syms, changed_syms, names_only=False,
-                demangle=True):
+def report_diff(
+    added_syms, removed_syms, changed_syms, names_only=False, demangle=True
+):
     def maybe_demangle(name):
         return util.demangle_symbol(name) if demangle else name
 
-    report = ''
+    report = ""
     for sym in added_syms:
-        report += 'Symbol added: %s\n' % maybe_demangle(sym['name'])
+        report += "Symbol added: %s\n" % maybe_demangle(sym["name"])
         if not names_only:
-            report += '    %s\n\n' % sym
+            report += "    %s\n\n" % sym
     if added_syms and names_only:
-        report += '\n'
+        report += "\n"
     for sym in removed_syms:
-        report += 'SYMBOL REMOVED: %s\n' % maybe_demangle(sym['name'])
+        report += "SYMBOL REMOVED: %s\n" % maybe_demangle(sym["name"])
         if not names_only:
-            report += '    %s\n\n' % sym
+            report += "    %s\n\n" % sym
     if removed_syms and names_only:
-        report += '\n'
+        report += "\n"
     if not names_only:
         for sym_pair in changed_syms:
             old_sym, new_sym = sym_pair
-            old_str = '\n    OLD SYMBOL: %s' % old_sym
-            new_str = '\n    NEW SYMBOL: %s' % new_sym
-            report += ('SYMBOL CHANGED: %s%s%s\n\n' %
-                       (maybe_demangle(old_sym['name']),
-                        old_str, new_str))
+            old_str = "\n    OLD SYMBOL: %s" % old_sym
+            new_str = "\n    NEW SYMBOL: %s" % new_sym
+            report += "SYMBOL CHANGED: %s%s%s\n\n" % (
+                maybe_demangle(old_sym["name"]),
+                old_str,
+                new_str,
+            )
 
     added = bool(len(added_syms) != 0)
     abi_break = bool(len(removed_syms))
     if not names_only:
         abi_break = abi_break or len(changed_syms)
     if added or abi_break:
-        report += 'Summary\n'
-        report += '    Added:   %d\n' % len(added_syms)
-        report += '    Removed: %d\n' % len(removed_syms)
+        report += "Summary\n"
+        report += "    Added:   %d\n" % len(added_syms)
+        report += "    Removed: %d\n" % len(removed_syms)
         if not names_only:
-            report += '    Changed: %d\n' % len(changed_syms)
+            report += "    Changed: %d\n" % len(changed_syms)
         if not abi_break:
-            report += 'Symbols added.'
+            report += "Symbols added."
         else:
-            report += 'ABI BREAKAGE: SYMBOLS ADDED OR REMOVED!'
+            report += "ABI BREAKAGE: SYMBOLS ADDED OR REMOVED!"
     else:
-        report += 'Symbols match.'
-    is_different = abi_break or bool(len(added_syms)) \
-                   or bool(len(changed_syms))
+        report += "Symbols match."
+    is_different = abi_break or bool(len(added_syms)) or bool(len(changed_syms))
     return report, abi_break, is_different
diff --git a/libcxx/utils/libcxx/sym_check/extract.py b/libcxx/utils/libcxx/sym_check/extract.py
--- a/libcxx/utils/libcxx/sym_check/extract.py
+++ b/libcxx/utils/libcxx/sym_check/extract.py
@@ -1,11 +1,11 @@
 # -*- Python -*- vim: set syntax=python tabstop=4 expandtab cc=80:
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """
 extract - A set of function that extract symbol lists from shared libraries.
 """
@@ -18,7 +18,8 @@
 
 from libcxx.sym_check import util
 
-extract_ignore_names = ['_init', '_fini']
+extract_ignore_names = ["_init", "_fini"]
+
 
 class NMExtractor(object):
     """
@@ -30,7 +31,7 @@
         """
         Search for the nm executable and return the path.
         """
-        return shutil.which('nm')
+        return shutil.which("nm")
 
     def __init__(self, static_lib):
         """
@@ -43,11 +44,10 @@
             print("ERROR: Could not find nm")
             sys.exit(1)
         self.static_lib = static_lib
-        self.flags = ['-P', '-g']
-        if sys.platform.startswith('aix'):
+        self.flags = ["-P", "-g"]
+        if sys.platform.startswith("aix"):
             # AIX nm demangles symbols by default, so suppress that.
-            self.flags.append('-C')
-
+            self.flags.append("-C")
 
     def extract(self, lib):
         """
@@ -56,8 +56,7 @@
         """
         cmd = [self.nm_exe] + self.flags + [lib]
         out = subprocess.check_output(cmd).decode()
-        fmt_syms = (self._extract_sym(l)
-                    for l in out.splitlines() if l.strip())
+        fmt_syms = (self._extract_sym(l) for l in out.splitlines() if l.strip())
         # Cast symbol to string.
         final_syms = (repr(s) for s in fmt_syms if self._want_sym(s))
         # Make unique and sort strings.
@@ -71,15 +70,15 @@
         if len(bits) < 2:
             return None
         new_sym = {
-            'name': bits[0],
-            'type': bits[1],
-            'is_defined': (bits[1].lower() != 'u')
+            "name": bits[0],
+            "type": bits[1],
+            "is_defined": (bits[1].lower() != "u"),
         }
-        new_sym['name'] = new_sym['name'].replace('@@', '@')
+        new_sym["name"] = new_sym["name"].replace("@@", "@")
         new_sym = self._transform_sym_type(new_sym)
         # NM types which we want to save the size for.
-        if new_sym['type'] == 'OBJECT' and len(bits) > 3:
-            new_sym['size'] = int(bits[3], 16)
+        if new_sym["type"] == "OBJECT" and len(bits) > 3:
+            new_sym["size"] = int(bits[3], 16)
         return new_sym
 
     @staticmethod
@@ -89,11 +88,14 @@
         """
         if sym is None or len(sym) < 2:
             return False
-        if sym['name'] in extract_ignore_names:
+        if sym["name"] in extract_ignore_names:
             return False
-        bad_types = ['t', 'b', 'r', 'd', 'w']
-        return (sym['type'] not in bad_types
-                and sym['name'] not in ['__bss_start', '_end', '_edata'])
+        bad_types = ["t", "b", "r", "d", "w"]
+        return sym["type"] not in bad_types and sym["name"] not in [
+            "__bss_start",
+            "_end",
+            "_edata",
+        ]
 
     @staticmethod
     def _transform_sym_type(sym):
@@ -101,14 +103,15 @@
         Map the nm single letter output for type to either FUNC or OBJECT.
         If the type is not recognized it is left unchanged.
         """
-        func_types = ['T', 'W']
-        obj_types = ['B', 'D', 'R', 'V', 'S']
-        if sym['type'] in func_types:
-            sym['type'] = 'FUNC'
-        elif sym['type'] in obj_types:
-            sym['type'] = 'OBJECT'
+        func_types = ["T", "W"]
+        obj_types = ["B", "D", "R", "V", "S"]
+        if sym["type"] in func_types:
+            sym["type"] = "FUNC"
+        elif sym["type"] in obj_types:
+            sym["type"] = "OBJECT"
         return sym
 
+
 class ReadElfExtractor(object):
     """
     ReadElfExtractor - Extract symbol lists from libraries using readelf.
@@ -119,7 +122,7 @@
         """
         Search for the readelf executable and return the path.
         """
-        return shutil.which('readelf')
+        return shutil.which("readelf")
 
     def __init__(self, static_lib):
         """
@@ -133,7 +136,7 @@
             sys.exit(1)
         # TODO: Support readelf for reading symbols from archives
         assert not static_lib and "RealElf does not yet support static libs"
-        self.flags = ['--wide', '--symbols']
+        self.flags = ["--wide", "--symbols"]
 
     def extract(self, lib):
         """
@@ -155,18 +158,18 @@
             if len(parts) == 7:
                 continue
             new_sym = {
-                'name': parts[7],
-                'size': int(parts[2]),
-                'type': parts[3],
-                'is_defined': (parts[6] != 'UND')
+                "name": parts[7],
+                "size": int(parts[2]),
+                "type": parts[3],
+                "is_defined": (parts[6] != "UND"),
             }
-            assert new_sym['type'] in ['OBJECT', 'FUNC', 'NOTYPE', 'TLS']
-            if new_sym['name'] in extract_ignore_names:
+            assert new_sym["type"] in ["OBJECT", "FUNC", "NOTYPE", "TLS"]
+            if new_sym["name"] in extract_ignore_names:
                 continue
-            if new_sym['type'] == 'NOTYPE':
+            if new_sym["type"] == "NOTYPE":
                 continue
-            if new_sym['type'] == 'FUNC':
-                del new_sym['size']
+            if new_sym["type"] == "FUNC":
+                del new_sym["size"]
             new_syms += [new_sym]
         return new_syms
 
@@ -190,98 +193,100 @@
             end = len(lines)
         return lines[start:end]
 
+
 class AIXDumpExtractor(object):
-     """
-     AIXDumpExtractor - Extract symbol lists from libraries using AIX dump.
-     """
+    """
+    AIXDumpExtractor - Extract symbol lists from libraries using AIX dump.
+    """
 
-     @staticmethod
-     def find_tool():
-         """
-         Search for the dump executable and return the path.
-         """
-         return shutil.which('dump')
+    @staticmethod
+    def find_tool():
+        """
+        Search for the dump executable and return the path.
+        """
+        return shutil.which("dump")
 
-     def __init__(self, static_lib):
-         """
-         Initialize the dump executable and flags that will be used to
-         extract symbols from shared libraries.
-         """
-         # TODO: Support dump for reading symbols from static libraries
-         assert not static_lib and "static libs not yet supported with dump"
-         self.tool = self.find_tool()
-         if self.tool is None:
-             print("ERROR: Could not find dump")
-             sys.exit(1)
-         self.flags = ['-n', '-v']
-         object_mode = environ.get('OBJECT_MODE')
-         if object_mode == '32':
-             self.flags += ['-X32']
-         elif object_mode == '64':
-             self.flags += ['-X64']
-         else:
-             self.flags += ['-X32_64']
+    def __init__(self, static_lib):
+        """
+        Initialize the dump executable and flags that will be used to
+        extract symbols from shared libraries.
+        """
+        # TODO: Support dump for reading symbols from static libraries
+        assert not static_lib and "static libs not yet supported with dump"
+        self.tool = self.find_tool()
+        if self.tool is None:
+            print("ERROR: Could not find dump")
+            sys.exit(1)
+        self.flags = ["-n", "-v"]
+        object_mode = environ.get("OBJECT_MODE")
+        if object_mode == "32":
+            self.flags += ["-X32"]
+        elif object_mode == "64":
+            self.flags += ["-X64"]
+        else:
+            self.flags += ["-X32_64"]
 
-     def extract(self, lib):
-         """
-         Extract symbols from a library and return the results as a dict of
-         parsed symbols.
-         """
-         cmd = [self.tool] + self.flags + [lib]
-         out = subprocess.check_output(cmd).decode()
-         loader_syms = self.get_loader_symbol_table(out)
-         return self.process_syms(loader_syms)
+    def extract(self, lib):
+        """
+        Extract symbols from a library and return the results as a dict of
+        parsed symbols.
+        """
+        cmd = [self.tool] + self.flags + [lib]
+        out = subprocess.check_output(cmd).decode()
+        loader_syms = self.get_loader_symbol_table(out)
+        return self.process_syms(loader_syms)
 
-     def process_syms(self, sym_list):
-         new_syms = []
-         for s in sym_list:
-             parts = s.split()
-             if not parts:
-                 continue
-             assert len(parts) == 8 or len(parts) == 7
-             if len(parts) == 7:
-                 continue
-             new_sym = {
-                 'name': parts[7],
-                 'type': 'FUNC' if parts[4] == 'DS' else 'OBJECT',
-                 'is_defined': (parts[5] != 'EXTref'),
-                 'storage_mapping_class': parts[4],
-                 'import_export': parts[3]
-             }
-             if new_sym['name'] in extract_ignore_names:
-                 continue
-             new_syms += [new_sym]
-         return new_syms
+    def process_syms(self, sym_list):
+        new_syms = []
+        for s in sym_list:
+            parts = s.split()
+            if not parts:
+                continue
+            assert len(parts) == 8 or len(parts) == 7
+            if len(parts) == 7:
+                continue
+            new_sym = {
+                "name": parts[7],
+                "type": "FUNC" if parts[4] == "DS" else "OBJECT",
+                "is_defined": (parts[5] != "EXTref"),
+                "storage_mapping_class": parts[4],
+                "import_export": parts[3],
+            }
+            if new_sym["name"] in extract_ignore_names:
+                continue
+            new_syms += [new_sym]
+        return new_syms
 
-     def get_loader_symbol_table(self, out):
-         lines = out.splitlines()
-         return filter(lambda n: re.match(r'^\[[0-9]+\]', n), lines)
+    def get_loader_symbol_table(self, out):
+        lines = out.splitlines()
+        return filter(lambda n: re.match(r"^\[[0-9]+\]", n), lines)
 
-     @staticmethod
-     def is_shared_lib(lib):
-         """
-         Check for the shared object flag in XCOFF headers of the input file or
-         library archive.
-         """
-         dump = AIXDumpExtractor.find_tool()
-         if dump is None:
-             print("ERROR: Could not find dump")
-             sys.exit(1)
-         cmd = [dump, '-X32_64', '-ov', lib]
-         out = subprocess.check_output(cmd).decode()
-         return out.find("SHROBJ") != -1
+    @staticmethod
+    def is_shared_lib(lib):
+        """
+        Check for the shared object flag in XCOFF headers of the input file or
+        library archive.
+        """
+        dump = AIXDumpExtractor.find_tool()
+        if dump is None:
+            print("ERROR: Could not find dump")
+            sys.exit(1)
+        cmd = [dump, "-X32_64", "-ov", lib]
+        out = subprocess.check_output(cmd).decode()
+        return out.find("SHROBJ") != -1
 
 
 def is_static_library(lib_file):
-     """
-     Determine if a given library is static or shared.
-     """
-     if sys.platform.startswith('aix'):
-         # An AIX library could be both, but for simplicity assume it isn't.
-         return not AIXDumpExtractor.is_shared_lib(lib_file)
-     else:
-         _, ext = os.path.splitext(lib_file)
-         return ext == '.a'
+    """
+    Determine if a given library is static or shared.
+    """
+    if sys.platform.startswith("aix"):
+        # An AIX library could be both, but for simplicity assume it isn't.
+        return not AIXDumpExtractor.is_shared_lib(lib_file)
+    else:
+        _, ext = os.path.splitext(lib_file)
+        return ext == ".a"
+
 
 def extract_symbols(lib_file, static_lib=None):
     """
@@ -291,7 +296,7 @@
     """
     if static_lib is None:
         static_lib = is_static_library(lib_file)
-    if sys.platform.startswith('aix'):
+    if sys.platform.startswith("aix"):
         extractor = AIXDumpExtractor(static_lib=static_lib)
     elif ReadElfExtractor.find_tool() and not static_lib:
         extractor = ReadElfExtractor(static_lib=static_lib)
diff --git a/libcxx/utils/libcxx/sym_check/match.py b/libcxx/utils/libcxx/sym_check/match.py
--- a/libcxx/utils/libcxx/sym_check/match.py
+++ b/libcxx/utils/libcxx/sym_check/match.py
@@ -1,11 +1,11 @@
 # -*- Python -*- vim: set syntax=python tabstop=4 expandtab cc=80:
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """
 match - A set of functions for matching symbols in a list to a list of regexs
 """
@@ -14,19 +14,19 @@
 
 
 def find_and_report_matching(symbol_list, regex_list):
-    report = ''
+    report = ""
     found_count = 0
     for regex_str in regex_list:
         report += 'Matching regex "%s":\n' % regex_str
         matching_list = find_matching_symbols(symbol_list, regex_str)
         if not matching_list:
-            report += '    No matches found\n\n'
+            report += "    No matches found\n\n"
             continue
         # else
         found_count += len(matching_list)
         for m in matching_list:
-            report += '    MATCHES: %s\n' % m['name']
-        report += '\n'
+            report += "    MATCHES: %s\n" % m["name"]
+        report += "\n"
     return found_count, report
 
 
@@ -34,6 +34,6 @@
     regex = re.compile(regex_str)
     matching_list = []
     for s in symbol_list:
-        if regex.match(s['name']):
+        if regex.match(s["name"]):
             matching_list += [s]
     return matching_list
diff --git a/libcxx/utils/libcxx/sym_check/util.py b/libcxx/utils/libcxx/sym_check/util.py
--- a/libcxx/utils/libcxx/sym_check/util.py
+++ b/libcxx/utils/libcxx/sym_check/util.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 from pprint import pformat
 import ast
@@ -26,16 +26,16 @@
     """
     Read a list of symbols in from a file.
     """
-    with open(filename, 'r') as f:
+    with open(filename, "r") as f:
         data = f.read()
     return read_syms_from_list(data.splitlines())
 
 
 def read_exclusions(filename):
-    with open(filename, 'r') as f:
+    with open(filename, "r") as f:
         data = f.read()
     lines = [l.strip() for l in data.splitlines() if l.strip()]
-    lines = [l for l in lines if not l.startswith('#')]
+    lines = [l for l in lines if not l.startswith("#")]
     return lines
 
 
@@ -43,24 +43,24 @@
     """
     Write a list of symbols to the file named by out.
     """
-    out_str = ''
+    out_str = ""
     out_list = sym_list
-    out_list.sort(key=lambda x: x['name'])
+    out_list.sort(key=lambda x: x["name"])
     if filter is not None:
         out_list = filter(out_list)
     if names_only:
-        out_list = [sym['name'] for sym in out_list]
+        out_list = [sym["name"] for sym in out_list]
     for sym in out_list:
         # Use pformat for consistent ordering of keys.
-        out_str += pformat(sym, width=100000) + '\n'
+        out_str += pformat(sym, width=100000) + "\n"
     if out is None:
         sys.stdout.write(out_str)
     else:
-        with open(out, 'w') as f:
+        with open(out, "w") as f:
             f.write(out_str)
 
 
-_cppfilt_exe = shutil.which('c++filt')
+_cppfilt_exe = shutil.which("c++filt")
 
 
 def demangle_symbol(symbol):
@@ -73,35 +73,37 @@
 
 
 def is_elf(filename):
-    with open(filename, 'rb') as f:
+    with open(filename, "rb") as f:
         magic_bytes = f.read(4)
-    return magic_bytes == b'\x7fELF'
+    return magic_bytes == b"\x7fELF"
 
 
 def is_mach_o(filename):
-    with open(filename, 'rb') as f:
+    with open(filename, "rb") as f:
         magic_bytes = f.read(4)
     return magic_bytes in [
-        b'\xfe\xed\xfa\xce',  # MH_MAGIC
-        b'\xce\xfa\xed\xfe',  # MH_CIGAM
-        b'\xfe\xed\xfa\xcf',  # MH_MAGIC_64
-        b'\xcf\xfa\xed\xfe',  # MH_CIGAM_64
-        b'\xca\xfe\xba\xbe',  # FAT_MAGIC
-        b'\xbe\xba\xfe\xca'   # FAT_CIGAM
+        b"\xfe\xed\xfa\xce",  # MH_MAGIC
+        b"\xce\xfa\xed\xfe",  # MH_CIGAM
+        b"\xfe\xed\xfa\xcf",  # MH_MAGIC_64
+        b"\xcf\xfa\xed\xfe",  # MH_CIGAM_64
+        b"\xca\xfe\xba\xbe",  # FAT_MAGIC
+        b"\xbe\xba\xfe\xca",  # FAT_CIGAM
     ]
 
+
 def is_xcoff_or_big_ar(filename):
-    with open(filename, 'rb') as f:
+    with open(filename, "rb") as f:
         magic_bytes = f.read(7)
-    return magic_bytes[:4] in [
-        b'\x01DF',  # XCOFF32
-        b'\x01F7'   # XCOFF64
-    ] or magic_bytes == b'<bigaf>'
+    return (
+        magic_bytes[:4] in [b"\x01DF", b"\x01F7"]  # XCOFF32  # XCOFF64
+        or magic_bytes == b"<bigaf>"
+    )
+
 
 def is_library_file(filename):
-    if sys.platform == 'darwin':
+    if sys.platform == "darwin":
         return is_mach_o(filename)
-    elif sys.platform.startswith('aix'):
+    elif sys.platform.startswith("aix"):
         return is_xcoff_or_big_ar(filename)
     else:
         return is_elf(filename)
@@ -109,169 +111,167 @@
 
 def extract_or_load(filename):
     import libcxx.sym_check.extract
+
     if is_library_file(filename):
         return libcxx.sym_check.extract.extract_symbols(filename)
     return read_syms_from_file(filename)
 
+
 def adjust_mangled_name(name):
-    if not name.startswith('__Z'):
+    if not name.startswith("__Z"):
         return name
     return name[1:]
 
-new_delete_std_symbols = [
-    '_Znam',
-    '_Znwm',
-    '_ZdaPv',
-    '_ZdaPvm',
-    '_ZdlPv',
-    '_ZdlPvm'
-]
+
+new_delete_std_symbols = ["_Znam", "_Znwm", "_ZdaPv", "_ZdaPvm", "_ZdlPv", "_ZdlPvm"]
 
 cxxabi_symbols = [
-    '___dynamic_cast',
-    '___gxx_personality_v0',
-    '_ZTIDi',
-    '_ZTIDn',
-    '_ZTIDs',
-    '_ZTIPDi',
-    '_ZTIPDn',
-    '_ZTIPDs',
-    '_ZTIPKDi',
-    '_ZTIPKDn',
-    '_ZTIPKDs',
-    '_ZTIPKa',
-    '_ZTIPKb',
-    '_ZTIPKc',
-    '_ZTIPKd',
-    '_ZTIPKe',
-    '_ZTIPKf',
-    '_ZTIPKh',
-    '_ZTIPKi',
-    '_ZTIPKj',
-    '_ZTIPKl',
-    '_ZTIPKm',
-    '_ZTIPKs',
-    '_ZTIPKt',
-    '_ZTIPKv',
-    '_ZTIPKw',
-    '_ZTIPKx',
-    '_ZTIPKy',
-    '_ZTIPa',
-    '_ZTIPb',
-    '_ZTIPc',
-    '_ZTIPd',
-    '_ZTIPe',
-    '_ZTIPf',
-    '_ZTIPh',
-    '_ZTIPi',
-    '_ZTIPj',
-    '_ZTIPl',
-    '_ZTIPm',
-    '_ZTIPs',
-    '_ZTIPt',
-    '_ZTIPv',
-    '_ZTIPw',
-    '_ZTIPx',
-    '_ZTIPy',
-    '_ZTIa',
-    '_ZTIb',
-    '_ZTIc',
-    '_ZTId',
-    '_ZTIe',
-    '_ZTIf',
-    '_ZTIh',
-    '_ZTIi',
-    '_ZTIj',
-    '_ZTIl',
-    '_ZTIm',
-    '_ZTIs',
-    '_ZTIt',
-    '_ZTIv',
-    '_ZTIw',
-    '_ZTIx',
-    '_ZTIy',
-    '_ZTSDi',
-    '_ZTSDn',
-    '_ZTSDs',
-    '_ZTSPDi',
-    '_ZTSPDn',
-    '_ZTSPDs',
-    '_ZTSPKDi',
-    '_ZTSPKDn',
-    '_ZTSPKDs',
-    '_ZTSPKa',
-    '_ZTSPKb',
-    '_ZTSPKc',
-    '_ZTSPKd',
-    '_ZTSPKe',
-    '_ZTSPKf',
-    '_ZTSPKh',
-    '_ZTSPKi',
-    '_ZTSPKj',
-    '_ZTSPKl',
-    '_ZTSPKm',
-    '_ZTSPKs',
-    '_ZTSPKt',
-    '_ZTSPKv',
-    '_ZTSPKw',
-    '_ZTSPKx',
-    '_ZTSPKy',
-    '_ZTSPa',
-    '_ZTSPb',
-    '_ZTSPc',
-    '_ZTSPd',
-    '_ZTSPe',
-    '_ZTSPf',
-    '_ZTSPh',
-    '_ZTSPi',
-    '_ZTSPj',
-    '_ZTSPl',
-    '_ZTSPm',
-    '_ZTSPs',
-    '_ZTSPt',
-    '_ZTSPv',
-    '_ZTSPw',
-    '_ZTSPx',
-    '_ZTSPy',
-    '_ZTSa',
-    '_ZTSb',
-    '_ZTSc',
-    '_ZTSd',
-    '_ZTSe',
-    '_ZTSf',
-    '_ZTSh',
-    '_ZTSi',
-    '_ZTSj',
-    '_ZTSl',
-    '_ZTSm',
-    '_ZTSs',
-    '_ZTSt',
-    '_ZTSv',
-    '_ZTSw',
-    '_ZTSx',
-    '_ZTSy'
+    "___dynamic_cast",
+    "___gxx_personality_v0",
+    "_ZTIDi",
+    "_ZTIDn",
+    "_ZTIDs",
+    "_ZTIPDi",
+    "_ZTIPDn",
+    "_ZTIPDs",
+    "_ZTIPKDi",
+    "_ZTIPKDn",
+    "_ZTIPKDs",
+    "_ZTIPKa",
+    "_ZTIPKb",
+    "_ZTIPKc",
+    "_ZTIPKd",
+    "_ZTIPKe",
+    "_ZTIPKf",
+    "_ZTIPKh",
+    "_ZTIPKi",
+    "_ZTIPKj",
+    "_ZTIPKl",
+    "_ZTIPKm",
+    "_ZTIPKs",
+    "_ZTIPKt",
+    "_ZTIPKv",
+    "_ZTIPKw",
+    "_ZTIPKx",
+    "_ZTIPKy",
+    "_ZTIPa",
+    "_ZTIPb",
+    "_ZTIPc",
+    "_ZTIPd",
+    "_ZTIPe",
+    "_ZTIPf",
+    "_ZTIPh",
+    "_ZTIPi",
+    "_ZTIPj",
+    "_ZTIPl",
+    "_ZTIPm",
+    "_ZTIPs",
+    "_ZTIPt",
+    "_ZTIPv",
+    "_ZTIPw",
+    "_ZTIPx",
+    "_ZTIPy",
+    "_ZTIa",
+    "_ZTIb",
+    "_ZTIc",
+    "_ZTId",
+    "_ZTIe",
+    "_ZTIf",
+    "_ZTIh",
+    "_ZTIi",
+    "_ZTIj",
+    "_ZTIl",
+    "_ZTIm",
+    "_ZTIs",
+    "_ZTIt",
+    "_ZTIv",
+    "_ZTIw",
+    "_ZTIx",
+    "_ZTIy",
+    "_ZTSDi",
+    "_ZTSDn",
+    "_ZTSDs",
+    "_ZTSPDi",
+    "_ZTSPDn",
+    "_ZTSPDs",
+    "_ZTSPKDi",
+    "_ZTSPKDn",
+    "_ZTSPKDs",
+    "_ZTSPKa",
+    "_ZTSPKb",
+    "_ZTSPKc",
+    "_ZTSPKd",
+    "_ZTSPKe",
+    "_ZTSPKf",
+    "_ZTSPKh",
+    "_ZTSPKi",
+    "_ZTSPKj",
+    "_ZTSPKl",
+    "_ZTSPKm",
+    "_ZTSPKs",
+    "_ZTSPKt",
+    "_ZTSPKv",
+    "_ZTSPKw",
+    "_ZTSPKx",
+    "_ZTSPKy",
+    "_ZTSPa",
+    "_ZTSPb",
+    "_ZTSPc",
+    "_ZTSPd",
+    "_ZTSPe",
+    "_ZTSPf",
+    "_ZTSPh",
+    "_ZTSPi",
+    "_ZTSPj",
+    "_ZTSPl",
+    "_ZTSPm",
+    "_ZTSPs",
+    "_ZTSPt",
+    "_ZTSPv",
+    "_ZTSPw",
+    "_ZTSPx",
+    "_ZTSPy",
+    "_ZTSa",
+    "_ZTSb",
+    "_ZTSc",
+    "_ZTSd",
+    "_ZTSe",
+    "_ZTSf",
+    "_ZTSh",
+    "_ZTSi",
+    "_ZTSj",
+    "_ZTSl",
+    "_ZTSm",
+    "_ZTSs",
+    "_ZTSt",
+    "_ZTSv",
+    "_ZTSw",
+    "_ZTSx",
+    "_ZTSy",
 ]
 
+
 def is_stdlib_symbol_name(name, sym):
     name = adjust_mangled_name(name)
     if re.search("@GLIBC|@GCC", name):
         # Only when symbol is defined do we consider it ours
-        return sym['is_defined']
-    if re.search('(St[0-9])|(__cxa)|(__cxxabi)', name):
+        return sym["is_defined"]
+    if re.search("(St[0-9])|(__cxa)|(__cxxabi)", name):
         return True
     if name in new_delete_std_symbols:
         return True
     if name in cxxabi_symbols:
         return True
-    if name.startswith('_Z'):
+    if name.startswith("_Z"):
         return True
     return False
 
+
 def filter_stdlib_symbols(syms):
     stdlib_symbols = []
     other_symbols = []
     for s in syms:
-        canon_name = adjust_mangled_name(s['name'])
+        canon_name = adjust_mangled_name(s["name"])
         if not is_stdlib_symbol_name(canon_name, s):
             other_symbols += [s]
         else:
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -1,49 +1,55 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 import os
 
 
 def _getSubstitution(substitution, config):
-  for (orig, replacement) in config.substitutions:
-    if orig == substitution:
-      return replacement
-  raise ValueError('Substitution {} is not in the config.'.format(substitution))
+    for (orig, replacement) in config.substitutions:
+        if orig == substitution:
+            return replacement
+    raise ValueError("Substitution {} is not in the config.".format(substitution))
+
 
 def configure(parameters, features, config, lit_config):
-  note = lambda s: lit_config.note("({}) {}".format(config.name, s))
-  config.environment = dict(os.environ)
-
-  # Apply the actions supplied by parameters to the configuration first, since
-  # parameters are things that we request explicitly and which might influence
-  # what features are implicitly made available next.
-  for param in parameters:
-    actions = param.getActions(config, lit_config.params)
-    for action in actions:
-      action.applyTo(config)
-      if lit_config.debug:
-        note("Applied '{}' as a result of parameter '{}'".format(
-          action.pretty(config, lit_config.params),
-          param.pretty(config, lit_config.params)))
-
-  # Then, apply the automatically-detected features.
-  for feature in features:
-    actions = feature.getActions(config)
-    for action in actions:
-      action.applyTo(config)
-      if lit_config.debug:
-        note("Applied '{}' as a result of implicitly detected feature '{}'".format(
-          action.pretty(config, lit_config.params),
-          feature.pretty(config)))
-
-  # Print the basic substitutions
-  for sub in ('%{cxx}', '%{flags}', '%{compile_flags}', '%{link_flags}', '%{exec}'):
-    note("Using {} substitution: '{}'".format(sub, _getSubstitution(sub, config)))
-
-  # Print all available features
-  note("All available features: {}".format(', '.join(config.available_features)))
+    note = lambda s: lit_config.note("({}) {}".format(config.name, s))
+    config.environment = dict(os.environ)
+
+    # Apply the actions supplied by parameters to the configuration first, since
+    # parameters are things that we request explicitly and which might influence
+    # what features are implicitly made available next.
+    for param in parameters:
+        actions = param.getActions(config, lit_config.params)
+        for action in actions:
+            action.applyTo(config)
+            if lit_config.debug:
+                note(
+                    "Applied '{}' as a result of parameter '{}'".format(
+                        action.pretty(config, lit_config.params),
+                        param.pretty(config, lit_config.params),
+                    )
+                )
+
+    # Then, apply the automatically-detected features.
+    for feature in features:
+        actions = feature.getActions(config)
+        for action in actions:
+            action.applyTo(config)
+            if lit_config.debug:
+                note(
+                    "Applied '{}' as a result of implicitly detected feature '{}'".format(
+                        action.pretty(config, lit_config.params), feature.pretty(config)
+                    )
+                )
+
+    # Print the basic substitutions
+    for sub in ("%{cxx}", "%{flags}", "%{compile_flags}", "%{link_flags}", "%{exec}"):
+        note("Using {} substitution: '{}'".format(sub, _getSubstitution(sub, config)))
+
+    # Print all available features
+    note("All available features: {}".format(", ".join(config.available_features)))
diff --git a/libcxx/utils/libcxx/test/dsl.py b/libcxx/utils/libcxx/test/dsl.py
--- a/libcxx/utils/libcxx/test/dsl.py
+++ b/libcxx/utils/libcxx/test/dsl.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 import os
 import pickle
@@ -21,231 +21,274 @@
 import lit.TestRunner
 import lit.util
 
+
 class ConfigurationError(Exception):
-  pass
+    pass
+
 
 class ConfigurationCompilationError(ConfigurationError):
-  pass
+    pass
+
 
 class ConfigurationRuntimeError(ConfigurationError):
-  pass
+    pass
+
 
 def _memoizeExpensiveOperation(extractCacheKey):
-  """
-  Allows memoizing a very expensive operation.
-
-  We pickle the cache key to make sure we store an immutable representation
-  of it. If we stored an object and the object was referenced elsewhere, it
-  could be changed from under our feet, which would break the cache.
-
-  We also store the cache for a given function persistently across invocations
-  of Lit. This dramatically speeds up the configuration of the test suite when
-  invoking Lit repeatedly, which is important for developer workflow. However,
-  with the current implementation that does not synchronize updates to the
-  persistent cache, this also means that one should not call a memoized
-  operation from multiple threads. This should normally not be a problem
-  since Lit configuration is single-threaded.
-  """
-  def decorator(function):
-    def f(config, *args, **kwargs):
-      cacheRoot = os.path.join(config.test_exec_root, '__config_cache__')
-      persistentCache = os.path.join(cacheRoot, function.__name__)
-      if not os.path.exists(cacheRoot):
-        os.makedirs(cacheRoot)
-
-      cache = {}
-      # Load a cache from a previous Lit invocation if there is one.
-      if os.path.exists(persistentCache):
-        with open(persistentCache, 'rb') as cacheFile:
-          cache = pickle.load(cacheFile)
-
-      cacheKey = pickle.dumps(extractCacheKey(config, *args, **kwargs))
-      if cacheKey not in cache:
-        cache[cacheKey] = function(config, *args, **kwargs)
-        # Update the persistent cache so it knows about the new key
-        with open(persistentCache, 'wb') as cacheFile:
-          pickle.dump(cache, cacheFile)
-      return cache[cacheKey]
-    return f
-  return decorator
+    """
+    Allows memoizing a very expensive operation.
+
+    We pickle the cache key to make sure we store an immutable representation
+    of it. If we stored an object and the object was referenced elsewhere, it
+    could be changed from under our feet, which would break the cache.
+
+    We also store the cache for a given function persistently across invocations
+    of Lit. This dramatically speeds up the configuration of the test suite when
+    invoking Lit repeatedly, which is important for developer workflow. However,
+    with the current implementation that does not synchronize updates to the
+    persistent cache, this also means that one should not call a memoized
+    operation from multiple threads. This should normally not be a problem
+    since Lit configuration is single-threaded.
+    """
+
+    def decorator(function):
+        def f(config, *args, **kwargs):
+            cacheRoot = os.path.join(config.test_exec_root, "__config_cache__")
+            persistentCache = os.path.join(cacheRoot, function.__name__)
+            if not os.path.exists(cacheRoot):
+                os.makedirs(cacheRoot)
+
+            cache = {}
+            # Load a cache from a previous Lit invocation if there is one.
+            if os.path.exists(persistentCache):
+                with open(persistentCache, "rb") as cacheFile:
+                    cache = pickle.load(cacheFile)
+
+            cacheKey = pickle.dumps(extractCacheKey(config, *args, **kwargs))
+            if cacheKey not in cache:
+                cache[cacheKey] = function(config, *args, **kwargs)
+                # Update the persistent cache so it knows about the new key
+                with open(persistentCache, "wb") as cacheFile:
+                    pickle.dump(cache, cacheFile)
+            return cache[cacheKey]
+
+        return f
+
+    return decorator
+
 
 def _executeScriptInternal(test, commands):
-  """
-  Returns (stdout, stderr, exitCode, timeoutInfo)
+    """
+    Returns (stdout, stderr, exitCode, timeoutInfo)
+
+    TODO: This really should be easier to access from Lit itself
+    """
+    parsedCommands = libcxx.test.format.parseScript(test, preamble=commands)
+
+    litConfig = lit.LitConfig.LitConfig(
+        progname="lit",
+        path=[],
+        quiet=False,
+        useValgrind=False,
+        valgrindLeakCheck=False,
+        valgrindArgs=[],
+        noExecute=False,
+        debug=False,
+        isWindows=platform.system() == "Windows",
+        order="smart",
+        params={},
+    )
+    _, tmpBase = libcxx.test.format._getTempPaths(test)
+    execDir = os.path.dirname(test.getExecPath())
+    res = lit.TestRunner.executeScriptInternal(
+        test, litConfig, tmpBase, parsedCommands, execDir
+    )
+    if isinstance(res, lit.Test.Result):  # Handle failure to parse the Lit test
+        res = ("", res.output, 127, None)
+    (out, err, exitCode, timeoutInfo) = res
+
+    # TODO: As a temporary workaround until https://reviews.llvm.org/D81892 lands, manually
+    #       split any stderr output that is included in stdout. It shouldn't be there, but
+    #       the Lit internal shell conflates stderr and stdout.
+    conflatedErrorOutput = re.search("(# command stderr:.+$)", out, flags=re.DOTALL)
+    if conflatedErrorOutput:
+        conflatedErrorOutput = conflatedErrorOutput.group(0)
+        out = out[: -len(conflatedErrorOutput)]
+        err += conflatedErrorOutput
+
+    return (out, err, exitCode, timeoutInfo, parsedCommands)
 
-  TODO: This really should be easier to access from Lit itself
-  """
-  parsedCommands = libcxx.test.format.parseScript(test, preamble=commands)
-
-  litConfig = lit.LitConfig.LitConfig(
-    progname='lit',
-    path=[],
-    quiet=False,
-    useValgrind=False,
-    valgrindLeakCheck=False,
-    valgrindArgs=[],
-    noExecute=False,
-    debug=False,
-    isWindows=platform.system() == 'Windows',
-    order='smart',
-    params={})
-  _, tmpBase = libcxx.test.format._getTempPaths(test)
-  execDir = os.path.dirname(test.getExecPath())
-  res = lit.TestRunner.executeScriptInternal(test, litConfig, tmpBase, parsedCommands, execDir)
-  if isinstance(res, lit.Test.Result): # Handle failure to parse the Lit test
-    res = ('', res.output, 127, None)
-  (out, err, exitCode, timeoutInfo) = res
-
-  # TODO: As a temporary workaround until https://reviews.llvm.org/D81892 lands, manually
-  #       split any stderr output that is included in stdout. It shouldn't be there, but
-  #       the Lit internal shell conflates stderr and stdout.
-  conflatedErrorOutput = re.search("(# command stderr:.+$)", out, flags=re.DOTALL)
-  if conflatedErrorOutput:
-    conflatedErrorOutput = conflatedErrorOutput.group(0)
-    out = out[:-len(conflatedErrorOutput)]
-    err += conflatedErrorOutput
-
-  return (out, err, exitCode, timeoutInfo, parsedCommands)
 
 def _makeConfigTest(config):
-  # Make sure the support directories exist, which is needed to create
-  # the temporary file %t below.
-  sourceRoot = os.path.join(config.test_exec_root, '__config_src__')
-  execRoot = os.path.join(config.test_exec_root, '__config_exec__')
-  for supportDir in (sourceRoot, execRoot):
-    if not os.path.exists(supportDir):
-      os.makedirs(supportDir)
-
-  # Create a dummy test suite and single dummy test inside it. As part of
-  # the Lit configuration, automatically do the equivalent of 'mkdir %T'
-  # and 'rm -r %T' to avoid cluttering the build directory.
-  suite = lit.Test.TestSuite('__config__', sourceRoot, execRoot, config)
-  tmp = tempfile.NamedTemporaryFile(dir=sourceRoot, delete=False, suffix='.cpp')
-  tmp.close()
-  pathInSuite = [os.path.relpath(tmp.name, sourceRoot)]
-  class TestWrapper(lit.Test.Test):
-    def __enter__(self):
-      testDir, _ = libcxx.test.format._getTempPaths(self)
-      os.makedirs(testDir)
-      return self
-    def __exit__(self, *args):
-      testDir, _ = libcxx.test.format._getTempPaths(self)
-      shutil.rmtree(testDir)
-      os.remove(tmp.name)
-  return TestWrapper(suite, pathInSuite, config)
+    # Make sure the support directories exist, which is needed to create
+    # the temporary file %t below.
+    sourceRoot = os.path.join(config.test_exec_root, "__config_src__")
+    execRoot = os.path.join(config.test_exec_root, "__config_exec__")
+    for supportDir in (sourceRoot, execRoot):
+        if not os.path.exists(supportDir):
+            os.makedirs(supportDir)
+
+    # Create a dummy test suite and single dummy test inside it. As part of
+    # the Lit configuration, automatically do the equivalent of 'mkdir %T'
+    # and 'rm -r %T' to avoid cluttering the build directory.
+    suite = lit.Test.TestSuite("__config__", sourceRoot, execRoot, config)
+    tmp = tempfile.NamedTemporaryFile(dir=sourceRoot, delete=False, suffix=".cpp")
+    tmp.close()
+    pathInSuite = [os.path.relpath(tmp.name, sourceRoot)]
+
+    class TestWrapper(lit.Test.Test):
+        def __enter__(self):
+            testDir, _ = libcxx.test.format._getTempPaths(self)
+            os.makedirs(testDir)
+            return self
+
+        def __exit__(self, *args):
+            testDir, _ = libcxx.test.format._getTempPaths(self)
+            shutil.rmtree(testDir)
+            os.remove(tmp.name)
+
+    return TestWrapper(suite, pathInSuite, config)
+
 
 @_memoizeExpensiveOperation(lambda c, s, f=[]: (c.substitutions, c.environment, s, f))
 def sourceBuilds(config, source, additionalFlags=[]):
-  """
-  Return whether the program in the given string builds successfully.
-
-  This is done by compiling and linking a program that consists of the given
-  source with the %{cxx} substitution, and seeing whether that succeeds. If
-  any additional flags are passed, they are appended to the compiler invocation.
-  """
-  with _makeConfigTest(config) as test:
-    with open(test.getSourcePath(), 'w') as sourceFile:
-      sourceFile.write(source)
-    _, _, exitCode, _, _ = _executeScriptInternal(test, ['%{{build}} {}'.format(' '.join(additionalFlags))])
-    return exitCode == 0
+    """
+    Return whether the program in the given string builds successfully.
 
-@_memoizeExpensiveOperation(lambda c, p, args=None: (c.substitutions, c.environment, p, args))
+    This is done by compiling and linking a program that consists of the given
+    source with the %{cxx} substitution, and seeing whether that succeeds. If
+    any additional flags are passed, they are appended to the compiler invocation.
+    """
+    with _makeConfigTest(config) as test:
+        with open(test.getSourcePath(), "w") as sourceFile:
+            sourceFile.write(source)
+        _, _, exitCode, _, _ = _executeScriptInternal(
+            test, ["%{{build}} {}".format(" ".join(additionalFlags))]
+        )
+        return exitCode == 0
+
+
+@_memoizeExpensiveOperation(
+    lambda c, p, args=None: (c.substitutions, c.environment, p, args)
+)
 def programOutput(config, program, args=None):
-  """
-  Compiles a program for the test target, run it on the test target and return
-  the output.
+    """
+    Compiles a program for the test target, run it on the test target and return
+    the output.
 
-  Note that execution of the program is done through the %{exec} substitution,
-  which means that the program may be run on a remote host depending on what
-  %{exec} does.
-  """
-  if args is None:
-    args = []
-  with _makeConfigTest(config) as test:
-    with open(test.getSourcePath(), 'w') as source:
-      source.write(program)
-    _, err, exitCode, _, buildcmd = _executeScriptInternal(test, ['%{build}'])
-    if exitCode != 0:
-      raise ConfigurationCompilationError("Failed to build program, cmd:\n{}\nstderr is:\n{}".format(buildcmd, err))
-
-    out, err, exitCode, _, runcmd = _executeScriptInternal(test, ["%{{run}} {}".format(' '.join(args))])
-    if exitCode != 0:
-      raise ConfigurationRuntimeError("Failed to run program, cmd:\n{}\nstderr is:\n{}".format(runcmd, err))
-
-    actualOut = re.search("# command output:\n(.+)\n$", out, flags=re.DOTALL)
-    actualOut = actualOut.group(1) if actualOut else ""
-    return actualOut
-
-@_memoizeExpensiveOperation(lambda c, p, args=None: (c.substitutions, c.environment, p, args))
+    Note that execution of the program is done through the %{exec} substitution,
+    which means that the program may be run on a remote host depending on what
+    %{exec} does.
+    """
+    if args is None:
+        args = []
+    with _makeConfigTest(config) as test:
+        with open(test.getSourcePath(), "w") as source:
+            source.write(program)
+        _, err, exitCode, _, buildcmd = _executeScriptInternal(test, ["%{build}"])
+        if exitCode != 0:
+            raise ConfigurationCompilationError(
+                "Failed to build program, cmd:\n{}\nstderr is:\n{}".format(
+                    buildcmd, err
+                )
+            )
+
+        out, err, exitCode, _, runcmd = _executeScriptInternal(
+            test, ["%{{run}} {}".format(" ".join(args))]
+        )
+        if exitCode != 0:
+            raise ConfigurationRuntimeError(
+                "Failed to run program, cmd:\n{}\nstderr is:\n{}".format(runcmd, err)
+            )
+
+        actualOut = re.search("# command output:\n(.+)\n$", out, flags=re.DOTALL)
+        actualOut = actualOut.group(1) if actualOut else ""
+        return actualOut
+
+
+@_memoizeExpensiveOperation(
+    lambda c, p, args=None: (c.substitutions, c.environment, p, args)
+)
 def programSucceeds(config, program, args=None):
-  """
-  Compiles a program for the test target, run it on the test target and return
-  whether it completed successfully.
+    """
+    Compiles a program for the test target, run it on the test target and return
+    whether it completed successfully.
+
+    Note that execution of the program is done through the %{exec} substitution,
+    which means that the program may be run on a remote host depending on what
+    %{exec} does.
+    """
+    try:
+        programOutput(config, program, args)
+    except ConfigurationRuntimeError:
+        return False
+    return True
 
-  Note that execution of the program is done through the %{exec} substitution,
-  which means that the program may be run on a remote host depending on what
-  %{exec} does.
-  """
-  try:
-    programOutput(config, program, args)
-  except ConfigurationRuntimeError:
-    return False
-  return True
 
 @_memoizeExpensiveOperation(lambda c, f: (c.substitutions, c.environment, f))
 def hasCompileFlag(config, flag):
-  """
-  Return whether the compiler in the configuration supports a given compiler flag.
+    """
+    Return whether the compiler in the configuration supports a given compiler flag.
+
+    This is done by executing the %{cxx} substitution with the given flag and
+    checking whether that succeeds.
+    """
+    with _makeConfigTest(config) as test:
+        out, err, exitCode, timeoutInfo, _ = _executeScriptInternal(
+            test,
+            [
+                "%{{cxx}} -xc++ {} -Werror -fsyntax-only %{{flags}} %{{compile_flags}} {}".format(
+                    os.devnull, flag
+                )
+            ],
+        )
+        return exitCode == 0
 
-  This is done by executing the %{cxx} substitution with the given flag and
-  checking whether that succeeds.
-  """
-  with _makeConfigTest(config) as test:
-    out, err, exitCode, timeoutInfo, _ = _executeScriptInternal(test, [
-      "%{{cxx}} -xc++ {} -Werror -fsyntax-only %{{flags}} %{{compile_flags}} {}".format(os.devnull, flag)
-    ])
-    return exitCode == 0
 
 @_memoizeExpensiveOperation(lambda c, s: (c.substitutions, c.environment, s))
 def runScriptExitCode(config, script):
-  """
-  Runs the given script as a Lit test, and returns the exit code of the execution.
+    """
+    Runs the given script as a Lit test, and returns the exit code of the execution.
+
+    The script must be a list of commands, each of which being something that
+    could appear on the right-hand-side of a `RUN:` keyword.
+    """
+    with _makeConfigTest(config) as test:
+        _, _, exitCode, _, _ = _executeScriptInternal(test, script)
+        return exitCode
 
-  The script must be a list of commands, each of which being something that
-  could appear on the right-hand-side of a `RUN:` keyword.
-  """
-  with _makeConfigTest(config) as test:
-    _, _, exitCode, _, _ = _executeScriptInternal(test, script)
-    return exitCode
 
 @_memoizeExpensiveOperation(lambda c, s: (c.substitutions, c.environment, s))
 def commandOutput(config, command):
-  """
-  Runs the given script as a Lit test, and returns the output.
-  If the exit code isn't 0 an exception is raised.
+    """
+    Runs the given script as a Lit test, and returns the output.
+    If the exit code isn't 0 an exception is raised.
+
+    The script must be a list of commands, each of which being something that
+    could appear on the right-hand-side of a `RUN:` keyword.
+    """
+    with _makeConfigTest(config) as test:
+        out, err, exitCode, _, cmd = _executeScriptInternal(test, command)
+        if exitCode != 0:
+            raise ConfigurationRuntimeError(
+                "Failed to run command: {}\nstderr is:\n{}".format(cmd, err)
+            )
+        return out
 
-  The script must be a list of commands, each of which being something that
-  could appear on the right-hand-side of a `RUN:` keyword.
-  """
-  with _makeConfigTest(config) as test:
-    out, err, exitCode, _, cmd = _executeScriptInternal(test, command)
-    if exitCode != 0:
-     raise ConfigurationRuntimeError("Failed to run command: {}\nstderr is:\n{}".format(cmd, err))
-    return out
 
 @_memoizeExpensiveOperation(lambda c, l: (c.substitutions, c.environment, l))
 def hasAnyLocale(config, locales):
-  """
-  Return whether the runtime execution environment supports a given locale.
-  Different systems may use different names for a locale, so this function checks
-  whether any of the passed locale names is supported by setlocale() and returns
-  true if one of them works.
-
-  This is done by executing a program that tries to set the given locale using
-  %{exec} -- this means that the command may be executed on a remote host
-  depending on the %{exec} substitution.
-  """
-  program = """
+    """
+    Return whether the runtime execution environment supports a given locale.
+    Different systems may use different names for a locale, so this function checks
+    whether any of the passed locale names is supported by setlocale() and returns
+    true if one of them works.
+
+    This is done by executing a program that tries to set the given locale using
+    %{exec} -- this means that the command may be executed on a remote host
+    depending on the %{exec} substitution.
+    """
+    program = """
     #include <stddef.h>
     #if defined(_LIBCPP_HAS_NO_LOCALIZATION)
       int main(int, char**) { return 1; }
@@ -261,460 +304,532 @@
       }
     #endif
   """
-  return programSucceeds(config, program, args=[pipes.quote(l) for l in locales])
+    return programSucceeds(config, program, args=[pipes.quote(l) for l in locales])
 
-@_memoizeExpensiveOperation(lambda c, flags='': (c.substitutions, c.environment, flags))
-def compilerMacros(config, flags=''):
-  """
-  Return a dictionary of predefined compiler macros.
 
-  The keys are strings representing macros, and the values are strings
-  representing what each macro is defined to.
+@_memoizeExpensiveOperation(lambda c, flags="": (c.substitutions, c.environment, flags))
+def compilerMacros(config, flags=""):
+    """
+    Return a dictionary of predefined compiler macros.
 
-  If the optional `flags` argument (a string) is provided, these flags will
-  be added to the compiler invocation when generating the macros.
-  """
-  with _makeConfigTest(config) as test:
-    with open(test.getSourcePath(), 'w') as sourceFile:
-      sourceFile.write("""
+    The keys are strings representing macros, and the values are strings
+    representing what each macro is defined to.
+
+    If the optional `flags` argument (a string) is provided, these flags will
+    be added to the compiler invocation when generating the macros.
+    """
+    with _makeConfigTest(config) as test:
+        with open(test.getSourcePath(), "w") as sourceFile:
+            sourceFile.write(
+                """
       #if __has_include(<__config_site>)
       #  include <__config_site>
       #endif
-      """)
-    unparsedOutput, err, exitCode, _, cmd = _executeScriptInternal(test, [
-      "%{{cxx}} %s -dM -E %{{flags}} %{{compile_flags}} {}".format(flags)
-    ])
-    if exitCode != 0:
-      raise ConfigurationCompilationError("Failed to retrieve compiler macros, compiler invocation is:\n{}\nstderr is:\n{}".format(cmd, err))
-    parsedMacros = dict()
-    defines = (l.strip() for l in unparsedOutput.split('\n') if l.startswith('#define '))
-    for line in defines:
-      line = line[len('#define '):]
-      macro, _, value = line.partition(' ')
-      parsedMacros[macro] = value
-    return parsedMacros
-
-def featureTestMacros(config, flags=''):
-  """
-  Return a dictionary of feature test macros.
+      """
+            )
+        unparsedOutput, err, exitCode, _, cmd = _executeScriptInternal(
+            test, ["%{{cxx}} %s -dM -E %{{flags}} %{{compile_flags}} {}".format(flags)]
+        )
+        if exitCode != 0:
+            raise ConfigurationCompilationError(
+                "Failed to retrieve compiler macros, compiler invocation is:\n{}\nstderr is:\n{}".format(
+                    cmd, err
+                )
+            )
+        parsedMacros = dict()
+        defines = (
+            l.strip() for l in unparsedOutput.split("\n") if l.startswith("#define ")
+        )
+        for line in defines:
+            line = line[len("#define ") :]
+            macro, _, value = line.partition(" ")
+            parsedMacros[macro] = value
+        return parsedMacros
+
+
+def featureTestMacros(config, flags=""):
+    """
+    Return a dictionary of feature test macros.
+
+    The keys are strings representing feature test macros, and the values are
+    integers representing the value of the macro.
+    """
+    allMacros = compilerMacros(config, flags)
+    return {
+        m: int(v.rstrip("LlUu"))
+        for (m, v) in allMacros.items()
+        if m.startswith("__cpp_")
+    }
 
-  The keys are strings representing feature test macros, and the values are
-  integers representing the value of the macro.
-  """
-  allMacros = compilerMacros(config, flags)
-  return {m: int(v.rstrip('LlUu')) for (m, v) in allMacros.items() if m.startswith('__cpp_')}
 
 def _appendToSubstitution(substitutions, key, value):
-  return [(k, v + ' ' + value) if k == key else (k, v) for (k, v) in substitutions]
+    return [(k, v + " " + value) if k == key else (k, v) for (k, v) in substitutions]
+
 
 def _prependToSubstitution(substitutions, key, value):
-  return [(k, value + ' ' + v) if k == key else (k, v) for (k, v) in substitutions]
+    return [(k, value + " " + v) if k == key else (k, v) for (k, v) in substitutions]
 
 
 class ConfigAction(object):
-  """
-  This class represents an action that can be performed on a Lit TestingConfig
-  object.
+    """
+    This class represents an action that can be performed on a Lit TestingConfig
+    object.
 
-  Examples of such actions are adding or modifying substitutions, Lit features,
-  etc. This class only provides the interface of such actions, and it is meant
-  to be subclassed appropriately to create new actions.
-  """
-  def applyTo(self, config):
+    Examples of such actions are adding or modifying substitutions, Lit features,
+    etc. This class only provides the interface of such actions, and it is meant
+    to be subclassed appropriately to create new actions.
     """
-    Applies the action to the given configuration.
 
-    This should modify the configuration object in place, and return nothing.
+    def applyTo(self, config):
+        """
+        Applies the action to the given configuration.
 
-    If applying the action to the configuration would yield an invalid
-    configuration, and it is possible to diagnose it here, this method
-    should produce an error. For example, it should be an error to modify
-    a substitution in a way that we know for sure is invalid (e.g. adding
-    a compiler flag when we know the compiler doesn't support it). Failure
-    to do so early may lead to difficult-to-diagnose issues down the road.
-    """
-    pass
+        This should modify the configuration object in place, and return nothing.
 
-  def pretty(self, config, litParams):
-    """
-    Returns a short and human-readable string describing what this action does.
+        If applying the action to the configuration would yield an invalid
+        configuration, and it is possible to diagnose it here, this method
+        should produce an error. For example, it should be an error to modify
+        a substitution in a way that we know for sure is invalid (e.g. adding
+        a compiler flag when we know the compiler doesn't support it). Failure
+        to do so early may lead to difficult-to-diagnose issues down the road.
+        """
+        pass
 
-    This is used for logging purposes when running the test suite, so it should
-    be kept concise.
-    """
-    pass
+    def pretty(self, config, litParams):
+        """
+        Returns a short and human-readable string describing what this action does.
+
+        This is used for logging purposes when running the test suite, so it should
+        be kept concise.
+        """
+        pass
 
 
 class AddFeature(ConfigAction):
-  """
-  This action defines the given Lit feature when running the test suite.
+    """
+    This action defines the given Lit feature when running the test suite.
 
-  The name of the feature can be a string or a callable, in which case it is
-  called with the configuration to produce the feature name (as a string).
-  """
-  def __init__(self, name):
-    self._name = name
+    The name of the feature can be a string or a callable, in which case it is
+    called with the configuration to produce the feature name (as a string).
+    """
 
-  def _getName(self, config):
-    name = self._name(config) if callable(self._name) else self._name
-    if not isinstance(name, str):
-      raise ValueError("Lit feature did not resolve to a string (got {})".format(name))
-    return name
+    def __init__(self, name):
+        self._name = name
 
-  def applyTo(self, config):
-    config.available_features.add(self._getName(config))
+    def _getName(self, config):
+        name = self._name(config) if callable(self._name) else self._name
+        if not isinstance(name, str):
+            raise ValueError(
+                "Lit feature did not resolve to a string (got {})".format(name)
+            )
+        return name
 
-  def pretty(self, config, litParams):
-    return 'add Lit feature {}'.format(self._getName(config))
+    def applyTo(self, config):
+        config.available_features.add(self._getName(config))
+
+    def pretty(self, config, litParams):
+        return "add Lit feature {}".format(self._getName(config))
 
 
 class AddFlag(ConfigAction):
-  """
-  This action adds the given flag to the %{flags} substitution.
+    """
+    This action adds the given flag to the %{flags} substitution.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    assert hasCompileFlag(config, flag), "Trying to enable flag {}, which is not supported".format(flag)
-    config.substitutions = _appendToSubstitution(config.substitutions, '%{flags}', flag)
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def pretty(self, config, litParams):
-    return 'add {} to %{{flags}}'.format(self._getFlag(config))
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        assert hasCompileFlag(
+            config, flag
+        ), "Trying to enable flag {}, which is not supported".format(flag)
+        config.substitutions = _appendToSubstitution(
+            config.substitutions, "%{flags}", flag
+        )
+
+    def pretty(self, config, litParams):
+        return "add {} to %{{flags}}".format(self._getFlag(config))
 
 
 class AddFlagIfSupported(ConfigAction):
-  """
-  This action adds the given flag to the %{flags} substitution, only if
-  the compiler supports the flag.
+    """
+    This action adds the given flag to the %{flags} substitution, only if
+    the compiler supports the flag.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
+
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    if hasCompileFlag(config, flag):
-      config.substitutions = _appendToSubstitution(config.substitutions, '%{flags}', flag)
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        if hasCompileFlag(config, flag):
+            config.substitutions = _appendToSubstitution(
+                config.substitutions, "%{flags}", flag
+            )
 
-  def pretty(self, config, litParams):
-    return 'add {} to %{{flags}}'.format(self._getFlag(config))
+    def pretty(self, config, litParams):
+        return "add {} to %{{flags}}".format(self._getFlag(config))
 
 
 class AddCompileFlag(ConfigAction):
-  """
-  This action adds the given flag to the %{compile_flags} substitution.
+    """
+    This action adds the given flag to the %{compile_flags} substitution.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
+
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    assert hasCompileFlag(config, flag), "Trying to enable compile flag {}, which is not supported".format(flag)
-    config.substitutions = _appendToSubstitution(config.substitutions, '%{compile_flags}', flag)
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        assert hasCompileFlag(
+            config, flag
+        ), "Trying to enable compile flag {}, which is not supported".format(flag)
+        config.substitutions = _appendToSubstitution(
+            config.substitutions, "%{compile_flags}", flag
+        )
 
-  def pretty(self, config, litParams):
-    return 'add {} to %{{compile_flags}}'.format(self._getFlag(config))
+    def pretty(self, config, litParams):
+        return "add {} to %{{compile_flags}}".format(self._getFlag(config))
 
 
 class AddLinkFlag(ConfigAction):
-  """
-  This action appends the given flag to the %{link_flags} substitution.
+    """
+    This action appends the given flag to the %{link_flags} substitution.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    assert hasCompileFlag(config, flag), "Trying to enable link flag {}, which is not supported".format(flag)
-    config.substitutions = _appendToSubstitution(config.substitutions, '%{link_flags}', flag)
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def pretty(self, config, litParams):
-    return 'append {} to %{{link_flags}}'.format(self._getFlag(config))
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        assert hasCompileFlag(
+            config, flag
+        ), "Trying to enable link flag {}, which is not supported".format(flag)
+        config.substitutions = _appendToSubstitution(
+            config.substitutions, "%{link_flags}", flag
+        )
+
+    def pretty(self, config, litParams):
+        return "append {} to %{{link_flags}}".format(self._getFlag(config))
 
 
 class PrependLinkFlag(ConfigAction):
-  """
-  This action prepends the given flag to the %{link_flags} substitution.
+    """
+    This action prepends the given flag to the %{link_flags} substitution.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    assert hasCompileFlag(config, flag), "Trying to enable link flag {}, which is not supported".format(flag)
-    config.substitutions = _prependToSubstitution(config.substitutions, '%{link_flags}', flag)
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def pretty(self, config, litParams):
-    return 'prepend {} to %{{link_flags}}'.format(self._getFlag(config))
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        assert hasCompileFlag(
+            config, flag
+        ), "Trying to enable link flag {}, which is not supported".format(flag)
+        config.substitutions = _prependToSubstitution(
+            config.substitutions, "%{link_flags}", flag
+        )
+
+    def pretty(self, config, litParams):
+        return "prepend {} to %{{link_flags}}".format(self._getFlag(config))
 
 
 class AddOptionalWarningFlag(ConfigAction):
-  """
-  This action adds the given warning flag to the %{compile_flags} substitution,
-  if it is supported by the compiler.
+    """
+    This action adds the given warning flag to the %{compile_flags} substitution,
+    if it is supported by the compiler.
 
-  The flag can be a string or a callable, in which case it is called with the
-  configuration to produce the actual flag (as a string).
-  """
-  def __init__(self, flag):
-    self._getFlag = lambda config: flag(config) if callable(flag) else flag
+    The flag can be a string or a callable, in which case it is called with the
+    configuration to produce the actual flag (as a string).
+    """
 
-  def applyTo(self, config):
-    flag = self._getFlag(config)
-    # Use -Werror to make sure we see an error about the flag being unsupported.
-    if hasCompileFlag(config, '-Werror ' + flag):
-      config.substitutions = _appendToSubstitution(config.substitutions, '%{compile_flags}', flag)
+    def __init__(self, flag):
+        self._getFlag = lambda config: flag(config) if callable(flag) else flag
 
-  def pretty(self, config, litParams):
-    return 'add {} to %{{compile_flags}}'.format(self._getFlag(config))
+    def applyTo(self, config):
+        flag = self._getFlag(config)
+        # Use -Werror to make sure we see an error about the flag being unsupported.
+        if hasCompileFlag(config, "-Werror " + flag):
+            config.substitutions = _appendToSubstitution(
+                config.substitutions, "%{compile_flags}", flag
+            )
 
+    def pretty(self, config, litParams):
+        return "add {} to %{{compile_flags}}".format(self._getFlag(config))
 
-class AddSubstitution(ConfigAction):
-  """
-  This action adds the given substitution to the Lit configuration.
 
-  The substitution can be a string or a callable, in which case it is called
-  with the configuration to produce the actual substitution (as a string).
-  """
-  def __init__(self, key, substitution):
-    self._key = key
-    self._getSub = lambda config: substitution(config) if callable(substitution) else substitution
+class AddSubstitution(ConfigAction):
+    """
+    This action adds the given substitution to the Lit configuration.
 
-  def applyTo(self, config):
-    key = self._key
-    sub = self._getSub(config)
-    config.substitutions.append((key, sub))
+    The substitution can be a string or a callable, in which case it is called
+    with the configuration to produce the actual substitution (as a string).
+    """
 
-  def pretty(self, config, litParams):
-    return 'add substitution {} = {}'.format(self._key, self._getSub(config))
+    def __init__(self, key, substitution):
+        self._key = key
+        self._getSub = (
+            lambda config: substitution(config)
+            if callable(substitution)
+            else substitution
+        )
 
+    def applyTo(self, config):
+        key = self._key
+        sub = self._getSub(config)
+        config.substitutions.append((key, sub))
 
-class Feature(object):
-  """
-  Represents a Lit available feature that is enabled whenever it is supported.
+    def pretty(self, config, litParams):
+        return "add substitution {} = {}".format(self._key, self._getSub(config))
 
-  A feature like this informs the test suite about a capability of the compiler,
-  platform, etc. Unlike Parameters, it does not make sense to explicitly
-  control whether a Feature is enabled -- it should be enabled whenever it
-  is supported.
-  """
-  def __init__(self, name, actions=None, when=lambda _: True):
-    """
-    Create a Lit feature for consumption by a test suite.
-
-    - name
-        The name of the feature. This is what will end up in Lit's available
-        features if the feature is enabled. This can be either a string or a
-        callable, in which case it is passed the TestingConfig and should
-        generate a string representing the name of the feature.
-
-    - actions
-        An optional list of ConfigActions to apply when the feature is supported.
-        An AddFeature action is always created regardless of any actions supplied
-        here -- these actions are meant to perform more than setting a corresponding
-        Lit feature (e.g. adding compiler flags). If 'actions' is a callable, it
-        is called with the current configuration object to generate the actual
-        list of actions.
-
-    - when
-        A callable that gets passed a TestingConfig and should return a
-        boolean representing whether the feature is supported in that
-        configuration. For example, this can use `hasCompileFlag` to
-        check whether the compiler supports the flag that the feature
-        represents. If omitted, the feature will always be considered
-        supported.
-    """
-    self._name = name
-    self._actions = [] if actions is None else actions
-    self._isSupported = when
-
-  def _getName(self, config):
-    name = self._name(config) if callable(self._name) else self._name
-    if not isinstance(name, str):
-      raise ValueError("Feature did not resolve to a name that's a string, got {}".format(name))
-    return name
-
-  def getActions(self, config):
-    """
-    Return the list of actions associated to this feature.
-
-    If the feature is not supported, an empty list is returned.
-    If the feature is supported, an `AddFeature` action is automatically added
-    to the returned list of actions, in addition to any actions provided on
-    construction.
-    """
-    if not self._isSupported(config):
-      return []
-    else:
-      actions = self._actions(config) if callable(self._actions) else self._actions
-      return [AddFeature(self._getName(config))] + actions
 
-  def pretty(self, config):
-    """
-    Returns the Feature's name.
+class Feature(object):
     """
-    return self._getName(config)
-
-
-def _str_to_bool(s):
-  """
-  Convert a string value to a boolean.
-
-  True values are "y", "yes", "t", "true", "on" and "1", regardless of capitalization.
-  False values are "n", "no", "f", "false", "off" and "0", regardless of capitalization.
-  """
-  trueVals = ["y", "yes", "t", "true", "on", "1"]
-  falseVals = ["n", "no", "f", "false", "off", "0"]
-  lower = s.lower()
-  if lower in trueVals:
-    return True
-  elif lower in falseVals:
-    return False
-  else:
-    raise ValueError("Got string '{}', which isn't a valid boolean".format(s))
-
-def _parse_parameter(s, type):
-  if type is bool and isinstance(s, str):
-    return _str_to_bool(s)
-  elif type is list and isinstance(s, str):
-    return [x.strip() for x in s.split(',') if x.strip()]
-  return type(s)
+    Represents a Lit available feature that is enabled whenever it is supported.
 
+    A feature like this informs the test suite about a capability of the compiler,
+    platform, etc. Unlike Parameters, it does not make sense to explicitly
+    control whether a Feature is enabled -- it should be enabled whenever it
+    is supported.
+    """
 
-class Parameter(object):
-  """
-  Represents a parameter of a Lit test suite.
-
-  Parameters are used to customize the behavior of test suites in a user
-  controllable way. There are two ways of setting the value of a Parameter.
-  The first one is to pass `--param <KEY>=<VALUE>` when running Lit (or
-  equivalently to set `litConfig.params[KEY] = VALUE` somewhere in the
-  Lit configuration files. This method will set the parameter globally for
-  all test suites being run.
-
-  The second method is to set `config.KEY = VALUE` somewhere in the Lit
-  configuration files, which sets the parameter only for the test suite(s)
-  that use that `config` object.
-
-  Parameters can have multiple possible values, and they can have a default
-  value when left unspecified. They can also have any number of ConfigActions
-  associated to them, in which case the actions will be performed on the
-  TestingConfig if the parameter is enabled. Depending on the actions
-  associated to a Parameter, it may be an error to enable the Parameter
-  if some actions are not supported in the given configuration. For example,
-  trying to set the compilation standard to C++23 when `-std=c++23` is not
-  supported by the compiler would be an error.
-  """
-  def __init__(self, name, type, help, actions, choices=None, default=None):
-    """
-    Create a Lit parameter to customize the behavior of a test suite.
-
-    - name
-        The name of the parameter that can be used to set it on the command-line.
-        On the command-line, the parameter can be set using `--param <name>=<value>`
-        when running Lit. This must be non-empty.
-
-    - choices
-        An optional non-empty set of possible values for this parameter. If provided,
-        this must be anything that can be iterated. It is an error if the parameter
-        is given a value that is not in that set, whether explicitly or through a
-        default value.
-
-    - type
-        A callable that can be used to parse the value of the parameter given
-        on the command-line. As a special case, using the type `bool` also
-        allows parsing strings with boolean-like contents, and the type `list`
-        will parse a string delimited by commas into a list of the substrings.
-
-    - help
-        A string explaining the parameter, for documentation purposes.
-        TODO: We should be able to surface those from the Lit command-line.
-
-    - actions
-        A callable that gets passed the parsed value of the parameter (either
-        the one passed on the command-line or the default one), and that returns
-        a list of ConfigAction to perform given the value of the parameter.
-        All the ConfigAction must be supported in the given configuration.
-
-    - default
-        An optional default value to use for the parameter when no value is
-        provided on the command-line. If the default value is a callable, it
-        is called with the TestingConfig and should return the default value
-        for the parameter. Whether the default value is computed or specified
-        directly, it must be in the 'choices' provided for that Parameter.
-    """
-    self._name = name
-    if len(self._name) == 0:
-      raise ValueError("Parameter name must not be the empty string")
-
-    if choices is not None:
-      self._choices = list(choices) # should be finite
-      if len(self._choices) == 0:
-        raise ValueError("Parameter '{}' must be given at least one possible value".format(self._name))
-    else:
-      self._choices = None
+    def __init__(self, name, actions=None, when=lambda _: True):
+        """
+        Create a Lit feature for consumption by a test suite.
+
+        - name
+            The name of the feature. This is what will end up in Lit's available
+            features if the feature is enabled. This can be either a string or a
+            callable, in which case it is passed the TestingConfig and should
+            generate a string representing the name of the feature.
+
+        - actions
+            An optional list of ConfigActions to apply when the feature is supported.
+            An AddFeature action is always created regardless of any actions supplied
+            here -- these actions are meant to perform more than setting a corresponding
+            Lit feature (e.g. adding compiler flags). If 'actions' is a callable, it
+            is called with the current configuration object to generate the actual
+            list of actions.
+
+        - when
+            A callable that gets passed a TestingConfig and should return a
+            boolean representing whether the feature is supported in that
+            configuration. For example, this can use `hasCompileFlag` to
+            check whether the compiler supports the flag that the feature
+            represents. If omitted, the feature will always be considered
+            supported.
+        """
+        self._name = name
+        self._actions = [] if actions is None else actions
+        self._isSupported = when
+
+    def _getName(self, config):
+        name = self._name(config) if callable(self._name) else self._name
+        if not isinstance(name, str):
+            raise ValueError(
+                "Feature did not resolve to a name that's a string, got {}".format(name)
+            )
+        return name
+
+    def getActions(self, config):
+        """
+        Return the list of actions associated to this feature.
+
+        If the feature is not supported, an empty list is returned.
+        If the feature is supported, an `AddFeature` action is automatically added
+        to the returned list of actions, in addition to any actions provided on
+        construction.
+        """
+        if not self._isSupported(config):
+            return []
+        else:
+            actions = (
+                self._actions(config) if callable(self._actions) else self._actions
+            )
+            return [AddFeature(self._getName(config))] + actions
+
+    def pretty(self, config):
+        """
+        Returns the Feature's name.
+        """
+        return self._getName(config)
 
-    self._parse = lambda x: _parse_parameter(x, type)
-    self._help = help
-    self._actions = actions
-    self._default = default
 
-  def _getValue(self, config, litParams):
-    """
-    Return the value of the parameter given the configuration objects.
+def _str_to_bool(s):
     """
-    param = getattr(config, self.name, None)
-    param = litParams.get(self.name, param)
-    if param is None and self._default is None:
-      raise ValueError("Parameter {} doesn't have a default value, but it was not specified in the Lit parameters or in the Lit config".format(self.name))
-    getDefault = lambda: self._default(config) if callable(self._default) else self._default
+    Convert a string value to a boolean.
 
-    if param is not None:
-      (pretty, value) = (param, self._parse(param))
+    True values are "y", "yes", "t", "true", "on" and "1", regardless of capitalization.
+    False values are "n", "no", "f", "false", "off" and "0", regardless of capitalization.
+    """
+    trueVals = ["y", "yes", "t", "true", "on", "1"]
+    falseVals = ["n", "no", "f", "false", "off", "0"]
+    lower = s.lower()
+    if lower in trueVals:
+        return True
+    elif lower in falseVals:
+        return False
     else:
-      value = getDefault()
-      pretty = '{} (default)'.format(value)
+        raise ValueError("Got string '{}', which isn't a valid boolean".format(s))
 
-    if self._choices and value not in self._choices:
-      raise ValueError("Got value '{}' for parameter '{}', which is not in the provided set of possible choices: {}".format(value, self.name, self._choices))
-    return (pretty, value)
 
-  @property
-  def name(self):
-    """
-    Return the name of the parameter.
+def _parse_parameter(s, type):
+    if type is bool and isinstance(s, str):
+        return _str_to_bool(s)
+    elif type is list and isinstance(s, str):
+        return [x.strip() for x in s.split(",") if x.strip()]
+    return type(s)
 
-    This is the name that can be used to set the parameter on the command-line
-    when running Lit.
-    """
-    return self._name
 
-  def getActions(self, config, litParams):
+class Parameter(object):
     """
-    Return the list of actions associated to this value of the parameter.
+    Represents a parameter of a Lit test suite.
+
+    Parameters are used to customize the behavior of test suites in a user
+    controllable way. There are two ways of setting the value of a Parameter.
+    The first one is to pass `--param <KEY>=<VALUE>` when running Lit (or
+    equivalently to set `litConfig.params[KEY] = VALUE` somewhere in the
+    Lit configuration files. This method will set the parameter globally for
+    all test suites being run.
+
+    The second method is to set `config.KEY = VALUE` somewhere in the Lit
+    configuration files, which sets the parameter only for the test suite(s)
+    that use that `config` object.
+
+    Parameters can have multiple possible values, and they can have a default
+    value when left unspecified. They can also have any number of ConfigActions
+    associated to them, in which case the actions will be performed on the
+    TestingConfig if the parameter is enabled. Depending on the actions
+    associated to a Parameter, it may be an error to enable the Parameter
+    if some actions are not supported in the given configuration. For example,
+    trying to set the compilation standard to C++23 when `-std=c++23` is not
+    supported by the compiler would be an error.
     """
-    (_, parameterValue) = self._getValue(config, litParams)
-    return self._actions(parameterValue)
 
-  def pretty(self, config, litParams):
-    """
-    Return a pretty representation of the parameter's name and value.
-    """
-    (prettyParameterValue, _) = self._getValue(config, litParams)
-    return "{}={}".format(self.name, prettyParameterValue)
+    def __init__(self, name, type, help, actions, choices=None, default=None):
+        """
+        Create a Lit parameter to customize the behavior of a test suite.
+
+        - name
+            The name of the parameter that can be used to set it on the command-line.
+            On the command-line, the parameter can be set using `--param <name>=<value>`
+            when running Lit. This must be non-empty.
+
+        - choices
+            An optional non-empty set of possible values for this parameter. If provided,
+            this must be anything that can be iterated. It is an error if the parameter
+            is given a value that is not in that set, whether explicitly or through a
+            default value.
+
+        - type
+            A callable that can be used to parse the value of the parameter given
+            on the command-line. As a special case, using the type `bool` also
+            allows parsing strings with boolean-like contents, and the type `list`
+            will parse a string delimited by commas into a list of the substrings.
+
+        - help
+            A string explaining the parameter, for documentation purposes.
+            TODO: We should be able to surface those from the Lit command-line.
+
+        - actions
+            A callable that gets passed the parsed value of the parameter (either
+            the one passed on the command-line or the default one), and that returns
+            a list of ConfigAction to perform given the value of the parameter.
+            All the ConfigAction must be supported in the given configuration.
+
+        - default
+            An optional default value to use for the parameter when no value is
+            provided on the command-line. If the default value is a callable, it
+            is called with the TestingConfig and should return the default value
+            for the parameter. Whether the default value is computed or specified
+            directly, it must be in the 'choices' provided for that Parameter.
+        """
+        self._name = name
+        if len(self._name) == 0:
+            raise ValueError("Parameter name must not be the empty string")
+
+        if choices is not None:
+            self._choices = list(choices)  # should be finite
+            if len(self._choices) == 0:
+                raise ValueError(
+                    "Parameter '{}' must be given at least one possible value".format(
+                        self._name
+                    )
+                )
+        else:
+            self._choices = None
+
+        self._parse = lambda x: _parse_parameter(x, type)
+        self._help = help
+        self._actions = actions
+        self._default = default
+
+    def _getValue(self, config, litParams):
+        """
+        Return the value of the parameter given the configuration objects.
+        """
+        param = getattr(config, self.name, None)
+        param = litParams.get(self.name, param)
+        if param is None and self._default is None:
+            raise ValueError(
+                "Parameter {} doesn't have a default value, but it was not specified in the Lit parameters or in the Lit config".format(
+                    self.name
+                )
+            )
+        getDefault = (
+            lambda: self._default(config) if callable(self._default) else self._default
+        )
+
+        if param is not None:
+            (pretty, value) = (param, self._parse(param))
+        else:
+            value = getDefault()
+            pretty = "{} (default)".format(value)
+
+        if self._choices and value not in self._choices:
+            raise ValueError(
+                "Got value '{}' for parameter '{}', which is not in the provided set of possible choices: {}".format(
+                    value, self.name, self._choices
+                )
+            )
+        return (pretty, value)
+
+    @property
+    def name(self):
+        """
+        Return the name of the parameter.
+
+        This is the name that can be used to set the parameter on the command-line
+        when running Lit.
+        """
+        return self._name
+
+    def getActions(self, config, litParams):
+        """
+        Return the list of actions associated to this value of the parameter.
+        """
+        (_, parameterValue) = self._getValue(config, litParams)
+        return self._actions(parameterValue)
+
+    def pretty(self, config, litParams):
+        """
+        Return a pretty representation of the parameter's name and value.
+        """
+        (prettyParameterValue, _) = self._getValue(config, litParams)
+        return "{}={}".format(self.name, prettyParameterValue)
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 from libcxx.test.dsl import *
 from lit.BooleanExpression import BooleanExpression
@@ -13,105 +13,174 @@
 import subprocess
 import sys
 
-_isClang      = lambda cfg: '__clang__' in compilerMacros(cfg) and '__apple_build_version__' not in compilerMacros(cfg)
-_isAppleClang = lambda cfg: '__apple_build_version__' in compilerMacros(cfg)
-_isGCC        = lambda cfg: '__GNUC__' in compilerMacros(cfg) and '__clang__' not in compilerMacros(cfg)
-_isMSVC       = lambda cfg: '_MSC_VER' in compilerMacros(cfg)
-_msvcVersion  = lambda cfg: (int(compilerMacros(cfg)['_MSC_VER']) // 100, int(compilerMacros(cfg)['_MSC_VER']) % 100)
+_isClang = lambda cfg: "__clang__" in compilerMacros(
+    cfg
+) and "__apple_build_version__" not in compilerMacros(cfg)
+_isAppleClang = lambda cfg: "__apple_build_version__" in compilerMacros(cfg)
+_isGCC = lambda cfg: "__GNUC__" in compilerMacros(
+    cfg
+) and "__clang__" not in compilerMacros(cfg)
+_isMSVC = lambda cfg: "_MSC_VER" in compilerMacros(cfg)
+_msvcVersion = lambda cfg: (
+    int(compilerMacros(cfg)["_MSC_VER"]) // 100,
+    int(compilerMacros(cfg)["_MSC_VER"]) % 100,
+)
 
-def _getSuitableClangTidy(cfg):
-  try:
-    # If we didn't build the libcxx-tidy plugin via CMake, we can't run the clang-tidy tests.
-    if runScriptExitCode(cfg, ['stat %{test-tools}/clang_tidy_checks/libcxx-tidy.plugin']) != 0:
-      return None
-
-    # TODO This should be the last stable release.
-    if runScriptExitCode(cfg, ['clang-tidy-16 --version']) == 0:
-      return 'clang-tidy-16'
 
-    if int(re.search('[0-9]+', commandOutput(cfg, ['clang-tidy --version'])).group()) >= 16:
-      return 'clang-tidy'
+def _getSuitableClangTidy(cfg):
+    try:
+        # If we didn't build the libcxx-tidy plugin via CMake, we can't run the clang-tidy tests.
+        if (
+            runScriptExitCode(
+                cfg, ["stat %{test-tools}/clang_tidy_checks/libcxx-tidy.plugin"]
+            )
+            != 0
+        ):
+            return None
+
+        # TODO This should be the last stable release.
+        if runScriptExitCode(cfg, ["clang-tidy-16 --version"]) == 0:
+            return "clang-tidy-16"
+
+        if (
+            int(
+                re.search(
+                    "[0-9]+", commandOutput(cfg, ["clang-tidy --version"])
+                ).group()
+            )
+            >= 16
+        ):
+            return "clang-tidy"
+
+    except ConfigurationRuntimeError:
+        return None
 
-  except ConfigurationRuntimeError:
-    return None
 
 DEFAULT_FEATURES = [
-  Feature(name='thread-safety',
-          when=lambda cfg: hasCompileFlag(cfg, '-Werror=thread-safety'),
-          actions=[AddCompileFlag('-Werror=thread-safety')]),
-
-  Feature(name='diagnose-if-support',
-          when=lambda cfg: hasCompileFlag(cfg, '-Wuser-defined-warnings'),
-          actions=[AddCompileFlag('-Wuser-defined-warnings')]),
-
-  # Tests to validate whether the compiler has a way to set the maximum number
-  # of steps during constant evaluation. Since the flag differs per compiler
-  # store the "valid" flag as a feature. This allows passing the proper compile
-  # flag to the compiler:
-  # // ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=12345678
-  # // ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-ops-limit): -fconstexpr-ops-limit=12345678
-  Feature(name='has-fconstexpr-steps',
-          when=lambda cfg: hasCompileFlag(cfg, '-fconstexpr-steps=1')),
-
-  Feature(name='has-fconstexpr-ops-limit',
-          when=lambda cfg: hasCompileFlag(cfg, '-fconstexpr-ops-limit=1')),
-
-  Feature(name='has-fblocks',                   when=lambda cfg: hasCompileFlag(cfg, '-fblocks')),
-  Feature(name='-fsized-deallocation',          when=lambda cfg: hasCompileFlag(cfg, '-fsized-deallocation')),
-  Feature(name='-faligned-allocation',          when=lambda cfg: hasCompileFlag(cfg, '-faligned-allocation')),
-  Feature(name='fdelayed-template-parsing',     when=lambda cfg: hasCompileFlag(cfg, '-fdelayed-template-parsing')),
-  Feature(name='libcpp-no-coroutines',          when=lambda cfg: featureTestMacros(cfg).get('__cpp_impl_coroutine', 0) < 201902),
-  Feature(name='has-fobjc-arc',                 when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc') and
-                                                                 sys.platform.lower().strip() == 'darwin'), # TODO: this doesn't handle cross-compiling to Apple platforms.
-  Feature(name='objective-c++',                 when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc')),
-  Feature(name='verify-support',                when=lambda cfg: hasCompileFlag(cfg, '-Xclang -verify-ignore-unexpected')),
-
-  Feature(name='non-lockfree-atomics',
-          when=lambda cfg: sourceBuilds(cfg, """
+    Feature(
+        name="thread-safety",
+        when=lambda cfg: hasCompileFlag(cfg, "-Werror=thread-safety"),
+        actions=[AddCompileFlag("-Werror=thread-safety")],
+    ),
+    Feature(
+        name="diagnose-if-support",
+        when=lambda cfg: hasCompileFlag(cfg, "-Wuser-defined-warnings"),
+        actions=[AddCompileFlag("-Wuser-defined-warnings")],
+    ),
+    # Tests to validate whether the compiler has a way to set the maximum number
+    # of steps during constant evaluation. Since the flag differs per compiler
+    # store the "valid" flag as a feature. This allows passing the proper compile
+    # flag to the compiler:
+    # // ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=12345678
+    # // ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-ops-limit): -fconstexpr-ops-limit=12345678
+    Feature(
+        name="has-fconstexpr-steps",
+        when=lambda cfg: hasCompileFlag(cfg, "-fconstexpr-steps=1"),
+    ),
+    Feature(
+        name="has-fconstexpr-ops-limit",
+        when=lambda cfg: hasCompileFlag(cfg, "-fconstexpr-ops-limit=1"),
+    ),
+    Feature(name="has-fblocks", when=lambda cfg: hasCompileFlag(cfg, "-fblocks")),
+    Feature(
+        name="-fsized-deallocation",
+        when=lambda cfg: hasCompileFlag(cfg, "-fsized-deallocation"),
+    ),
+    Feature(
+        name="-faligned-allocation",
+        when=lambda cfg: hasCompileFlag(cfg, "-faligned-allocation"),
+    ),
+    Feature(
+        name="fdelayed-template-parsing",
+        when=lambda cfg: hasCompileFlag(cfg, "-fdelayed-template-parsing"),
+    ),
+    Feature(
+        name="libcpp-no-coroutines",
+        when=lambda cfg: featureTestMacros(cfg).get("__cpp_impl_coroutine", 0) < 201902,
+    ),
+    Feature(
+        name="has-fobjc-arc",
+        when=lambda cfg: hasCompileFlag(cfg, "-xobjective-c++ -fobjc-arc")
+        and sys.platform.lower().strip() == "darwin",
+    ),  # TODO: this doesn't handle cross-compiling to Apple platforms.
+    Feature(
+        name="objective-c++",
+        when=lambda cfg: hasCompileFlag(cfg, "-xobjective-c++ -fobjc-arc"),
+    ),
+    Feature(
+        name="verify-support",
+        when=lambda cfg: hasCompileFlag(cfg, "-Xclang -verify-ignore-unexpected"),
+    ),
+    Feature(
+        name="non-lockfree-atomics",
+        when=lambda cfg: sourceBuilds(
+            cfg,
+            """
             #include <atomic>
             struct Large { int storage[100]; };
             std::atomic<Large> x;
             int main(int, char**) { (void)x.load(); return 0; }
-          """)),
-  # TODO: Remove this feature once compiler-rt includes __atomic_is_lockfree()
-  # on all supported platforms.
-  Feature(name='is-lockfree-runtime-function',
-          when=lambda cfg: sourceBuilds(cfg, """
+          """,
+        ),
+    ),
+    # TODO: Remove this feature once compiler-rt includes __atomic_is_lockfree()
+    # on all supported platforms.
+    Feature(
+        name="is-lockfree-runtime-function",
+        when=lambda cfg: sourceBuilds(
+            cfg,
+            """
             #include <atomic>
             struct Large { int storage[100]; };
             std::atomic<Large> x;
             int main(int, char**) { return x.is_lock_free(); }
-          """)),
-
-  # Some tests rely on creating shared libraries which link in the C++ Standard Library. In some
-  # cases, this doesn't work (e.g. if the library was built as a static archive and wasn't compiled
-  # as position independent). This feature informs the test suite of whether it's possible to create
-  # a shared library in a shell test by using the '-shared' compiler flag.
-  #
-  # Note: To implement this check properly, we need to make sure that we use something inside the
-  # compiled library, not only in the headers. It should be safe to assume that all implementations
-  # define `operator new` in the compiled library.
-  Feature(name='cant-build-shared-library',
-          when=lambda cfg: not sourceBuilds(cfg, """
+          """,
+        ),
+    ),
+    # Some tests rely on creating shared libraries which link in the C++ Standard Library. In some
+    # cases, this doesn't work (e.g. if the library was built as a static archive and wasn't compiled
+    # as position independent). This feature informs the test suite of whether it's possible to create
+    # a shared library in a shell test by using the '-shared' compiler flag.
+    #
+    # Note: To implement this check properly, we need to make sure that we use something inside the
+    # compiled library, not only in the headers. It should be safe to assume that all implementations
+    # define `operator new` in the compiled library.
+    Feature(
+        name="cant-build-shared-library",
+        when=lambda cfg: not sourceBuilds(
+            cfg,
+            """
             void f() { new int(3); }
-          """, ['-shared'])),
-
-  # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.20348.0):
-  # https://developercommunity.visualstudio.com/t/utf-8-locales-break-ctype-functions-for-wchar-type/1653678
-  Feature(name='win32-broken-utf8-wchar-ctype',
-          when=lambda cfg: not '_LIBCPP_HAS_NO_LOCALIZATION' in compilerMacros(cfg) and '_WIN32' in compilerMacros(cfg) and not programSucceeds(cfg, """
+          """,
+            ["-shared"],
+        ),
+    ),
+    # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.20348.0):
+    # https://developercommunity.visualstudio.com/t/utf-8-locales-break-ctype-functions-for-wchar-type/1653678
+    Feature(
+        name="win32-broken-utf8-wchar-ctype",
+        when=lambda cfg: not "_LIBCPP_HAS_NO_LOCALIZATION" in compilerMacros(cfg)
+        and "_WIN32" in compilerMacros(cfg)
+        and not programSucceeds(
+            cfg,
+            """
             #include <locale.h>
             #include <wctype.h>
             int main(int, char**) {
               setlocale(LC_ALL, "en_US.UTF-8");
               return towlower(L'\\xDA') != L'\\xFA';
             }
-          """)),
-
-  # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.19041.0).
-  # https://developercommunity.visualstudio.com/t/printf-formatting-with-g-outputs-too/1660837
-  Feature(name='win32-broken-printf-g-precision',
-          when=lambda cfg: '_WIN32' in compilerMacros(cfg) and not programSucceeds(cfg, """
+          """,
+        ),
+    ),
+    # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.19041.0).
+    # https://developercommunity.visualstudio.com/t/printf-formatting-with-g-outputs-too/1660837
+    Feature(
+        name="win32-broken-printf-g-precision",
+        when=lambda cfg: "_WIN32" in compilerMacros(cfg)
+        and not programSucceeds(
+            cfg,
+            """
             #include <stdio.h>
             #include <string.h>
             int main(int, char**) {
@@ -119,70 +188,126 @@
               snprintf(buf, sizeof(buf), "%#.*g", 0, 0.0);
               return strcmp(buf, "0.");
             }
-          """)),
-
-  # Check for Glibc < 2.27, where the ru_RU.UTF-8 locale had
-  # mon_decimal_point == ".", which our tests don't handle.
-  Feature(name='glibc-old-ru_RU-decimal-point',
-          when=lambda cfg: not '_LIBCPP_HAS_NO_LOCALIZATION' in compilerMacros(cfg) and not programSucceeds(cfg, """
+          """,
+        ),
+    ),
+    # Check for Glibc < 2.27, where the ru_RU.UTF-8 locale had
+    # mon_decimal_point == ".", which our tests don't handle.
+    Feature(
+        name="glibc-old-ru_RU-decimal-point",
+        when=lambda cfg: not "_LIBCPP_HAS_NO_LOCALIZATION" in compilerMacros(cfg)
+        and not programSucceeds(
+            cfg,
+            """
             #include <locale.h>
             #include <string.h>
             int main(int, char**) {
               setlocale(LC_ALL, "ru_RU.UTF-8");
               return strcmp(localeconv()->mon_decimal_point, ",");
             }
-          """)),
-
-  Feature(name='has-unix-headers',
-          when=lambda cfg: sourceBuilds(cfg, """
+          """,
+        ),
+    ),
+    Feature(
+        name="has-unix-headers",
+        when=lambda cfg: sourceBuilds(
+            cfg,
+            """
             #include <unistd.h>
             #include <sys/wait.h>
             int main(int, char**) {
               return 0;
             }
-          """)),
-
-  # Whether Bash can run on the executor.
-  # This is not always the case, for example when running on embedded systems.
-  #
-  # For the corner case of bash existing, but it being missing in the path
-  # set in %{exec} as "--env PATH=one-single-dir", the executor does find
-  # and executes bash, but bash then can't find any other common shell
-  # utilities. Test executing "bash -c 'bash --version'" to see if bash
-  # manages to find binaries to execute.
-  Feature(name='executor-has-no-bash',
-          when=lambda cfg: runScriptExitCode(cfg, ['%{exec} bash -c \'bash --version\'']) != 0),
-  Feature(name='has-clang-tidy',
-          when=lambda cfg: _getSuitableClangTidy(cfg) is not None,
-          actions=[AddSubstitution('%{clang-tidy}', lambda cfg: _getSuitableClangTidy(cfg))]),
-
-  Feature(name='apple-clang',                                                                                                      when=_isAppleClang),
-  Feature(name=lambda cfg: 'apple-clang-{__clang_major__}'.format(**compilerMacros(cfg)),                                          when=_isAppleClang),
-  Feature(name=lambda cfg: 'apple-clang-{__clang_major__}.{__clang_minor__}'.format(**compilerMacros(cfg)),                        when=_isAppleClang),
-  Feature(name=lambda cfg: 'apple-clang-{__clang_major__}.{__clang_minor__}.{__clang_patchlevel__}'.format(**compilerMacros(cfg)), when=_isAppleClang),
-
-  Feature(name='clang',                                                                                                            when=_isClang),
-  Feature(name=lambda cfg: 'clang-{__clang_major__}'.format(**compilerMacros(cfg)),                                                when=_isClang),
-  Feature(name=lambda cfg: 'clang-{__clang_major__}.{__clang_minor__}'.format(**compilerMacros(cfg)),                              when=_isClang),
-  Feature(name=lambda cfg: 'clang-{__clang_major__}.{__clang_minor__}.{__clang_patchlevel__}'.format(**compilerMacros(cfg)),       when=_isClang),
-
-  # Note: Due to a GCC bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104760), we must disable deprecation warnings
-  #       on GCC or spurious diagnostics are issued.
-  #
-  # TODO:
-  # - Enable -Wplacement-new with GCC.
-  # - Enable -Wclass-memaccess with GCC.
-  Feature(name='gcc',                                                                                                              when=_isGCC,
-          actions=[AddCompileFlag('-D_LIBCPP_DISABLE_DEPRECATION_WARNINGS'),
-                   AddCompileFlag('-Wno-placement-new'),
-                   AddCompileFlag('-Wno-class-memaccess')]),
-  Feature(name=lambda cfg: 'gcc-{__GNUC__}'.format(**compilerMacros(cfg)),                                                         when=_isGCC),
-  Feature(name=lambda cfg: 'gcc-{__GNUC__}.{__GNUC_MINOR__}'.format(**compilerMacros(cfg)),                                        when=_isGCC),
-  Feature(name=lambda cfg: 'gcc-{__GNUC__}.{__GNUC_MINOR__}.{__GNUC_PATCHLEVEL__}'.format(**compilerMacros(cfg)),                  when=_isGCC),
-
-  Feature(name='msvc',                                                                                                             when=_isMSVC),
-  Feature(name=lambda cfg: 'msvc-{}'.format(*_msvcVersion(cfg)),                                                                   when=_isMSVC),
-  Feature(name=lambda cfg: 'msvc-{}.{}'.format(*_msvcVersion(cfg)),                                                                when=_isMSVC),
+          """,
+        ),
+    ),
+    # Whether Bash can run on the executor.
+    # This is not always the case, for example when running on embedded systems.
+    #
+    # For the corner case of bash existing, but it being missing in the path
+    # set in %{exec} as "--env PATH=one-single-dir", the executor does find
+    # and executes bash, but bash then can't find any other common shell
+    # utilities. Test executing "bash -c 'bash --version'" to see if bash
+    # manages to find binaries to execute.
+    Feature(
+        name="executor-has-no-bash",
+        when=lambda cfg: runScriptExitCode(cfg, ["%{exec} bash -c 'bash --version'"])
+        != 0,
+    ),
+    Feature(
+        name="has-clang-tidy",
+        when=lambda cfg: _getSuitableClangTidy(cfg) is not None,
+        actions=[
+            AddSubstitution("%{clang-tidy}", lambda cfg: _getSuitableClangTidy(cfg))
+        ],
+    ),
+    Feature(name="apple-clang", when=_isAppleClang),
+    Feature(
+        name=lambda cfg: "apple-clang-{__clang_major__}".format(**compilerMacros(cfg)),
+        when=_isAppleClang,
+    ),
+    Feature(
+        name=lambda cfg: "apple-clang-{__clang_major__}.{__clang_minor__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isAppleClang,
+    ),
+    Feature(
+        name=lambda cfg: "apple-clang-{__clang_major__}.{__clang_minor__}.{__clang_patchlevel__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isAppleClang,
+    ),
+    Feature(name="clang", when=_isClang),
+    Feature(
+        name=lambda cfg: "clang-{__clang_major__}".format(**compilerMacros(cfg)),
+        when=_isClang,
+    ),
+    Feature(
+        name=lambda cfg: "clang-{__clang_major__}.{__clang_minor__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isClang,
+    ),
+    Feature(
+        name=lambda cfg: "clang-{__clang_major__}.{__clang_minor__}.{__clang_patchlevel__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isClang,
+    ),
+    # Note: Due to a GCC bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104760), we must disable deprecation warnings
+    #       on GCC or spurious diagnostics are issued.
+    #
+    # TODO:
+    # - Enable -Wplacement-new with GCC.
+    # - Enable -Wclass-memaccess with GCC.
+    Feature(
+        name="gcc",
+        when=_isGCC,
+        actions=[
+            AddCompileFlag("-D_LIBCPP_DISABLE_DEPRECATION_WARNINGS"),
+            AddCompileFlag("-Wno-placement-new"),
+            AddCompileFlag("-Wno-class-memaccess"),
+        ],
+    ),
+    Feature(
+        name=lambda cfg: "gcc-{__GNUC__}".format(**compilerMacros(cfg)), when=_isGCC
+    ),
+    Feature(
+        name=lambda cfg: "gcc-{__GNUC__}.{__GNUC_MINOR__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isGCC,
+    ),
+    Feature(
+        name=lambda cfg: "gcc-{__GNUC__}.{__GNUC_MINOR__}.{__GNUC_PATCHLEVEL__}".format(
+            **compilerMacros(cfg)
+        ),
+        when=_isGCC,
+    ),
+    Feature(name="msvc", when=_isMSVC),
+    Feature(name=lambda cfg: "msvc-{}".format(*_msvcVersion(cfg)), when=_isMSVC),
+    Feature(name=lambda cfg: "msvc-{}.{}".format(*_msvcVersion(cfg)), when=_isMSVC),
 ]
 
 # Deduce and add the test features that that are implied by the #defines in
@@ -196,54 +321,70 @@
 # Note that features that are more strongly tied to libc++ are named libcpp-foo,
 # while features that are more general in nature are not prefixed with 'libcpp-'.
 macros = {
-  '_LIBCPP_HAS_NO_MONOTONIC_CLOCK': 'no-monotonic-clock',
-  '_LIBCPP_HAS_NO_THREADS': 'no-threads',
-  '_LIBCPP_HAS_THREAD_API_EXTERNAL': 'libcpp-has-thread-api-external',
-  '_LIBCPP_HAS_THREAD_API_PTHREAD': 'libcpp-has-thread-api-pthread',
-  '_LIBCPP_NO_VCRUNTIME': 'libcpp-no-vcruntime',
-  '_LIBCPP_ABI_VERSION': 'libcpp-abi-version',
-  '_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY': 'no-filesystem',
-  '_LIBCPP_HAS_NO_RANDOM_DEVICE': 'no-random-device',
-  '_LIBCPP_HAS_NO_LOCALIZATION': 'no-localization',
-  '_LIBCPP_HAS_NO_FSTREAM': 'no-fstream',
-  '_LIBCPP_HAS_NO_WIDE_CHARACTERS': 'no-wide-characters',
-  '_LIBCPP_HAS_NO_UNICODE': 'libcpp-has-no-unicode',
-  '_LIBCPP_ENABLE_DEBUG_MODE': 'libcpp-has-debug-mode',
+    "_LIBCPP_HAS_NO_MONOTONIC_CLOCK": "no-monotonic-clock",
+    "_LIBCPP_HAS_NO_THREADS": "no-threads",
+    "_LIBCPP_HAS_THREAD_API_EXTERNAL": "libcpp-has-thread-api-external",
+    "_LIBCPP_HAS_THREAD_API_PTHREAD": "libcpp-has-thread-api-pthread",
+    "_LIBCPP_NO_VCRUNTIME": "libcpp-no-vcruntime",
+    "_LIBCPP_ABI_VERSION": "libcpp-abi-version",
+    "_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY": "no-filesystem",
+    "_LIBCPP_HAS_NO_RANDOM_DEVICE": "no-random-device",
+    "_LIBCPP_HAS_NO_LOCALIZATION": "no-localization",
+    "_LIBCPP_HAS_NO_FSTREAM": "no-fstream",
+    "_LIBCPP_HAS_NO_WIDE_CHARACTERS": "no-wide-characters",
+    "_LIBCPP_HAS_NO_UNICODE": "libcpp-has-no-unicode",
+    "_LIBCPP_ENABLE_DEBUG_MODE": "libcpp-has-debug-mode",
 }
 for macro, feature in macros.items():
-  DEFAULT_FEATURES.append(
-    Feature(name=lambda cfg, m=macro, f=feature: f + ('={}'.format(compilerMacros(cfg)[m]) if compilerMacros(cfg)[m] else ''),
-            when=lambda cfg, m=macro: m in compilerMacros(cfg))
-  )
+    DEFAULT_FEATURES.append(
+        Feature(
+            name=lambda cfg, m=macro, f=feature: f
+            + ("={}".format(compilerMacros(cfg)[m]) if compilerMacros(cfg)[m] else ""),
+            when=lambda cfg, m=macro: m in compilerMacros(cfg),
+        )
+    )
 
 
 # Mapping from canonical locale names (used in the tests) to possible locale
 # names on various systems. Each locale is considered supported if any of the
 # alternative names is supported.
 locales = {
-  'en_US.UTF-8':     ['en_US.UTF-8', 'en_US.utf8', 'English_United States.1252'],
-  'fr_FR.UTF-8':     ['fr_FR.UTF-8', 'fr_FR.utf8', 'French_France.1252'],
-  'ja_JP.UTF-8':     ['ja_JP.UTF-8', 'ja_JP.utf8', 'Japanese_Japan.923'],
-  'ru_RU.UTF-8':     ['ru_RU.UTF-8', 'ru_RU.utf8', 'Russian_Russia.1251'],
-  'zh_CN.UTF-8':     ['zh_CN.UTF-8', 'zh_CN.utf8', 'Chinese_China.936'],
-  'fr_CA.ISO8859-1': ['fr_CA.ISO8859-1', 'French_Canada.1252'],
-  'cs_CZ.ISO8859-2': ['cs_CZ.ISO8859-2', 'Czech_Czech Republic.1250']
+    "en_US.UTF-8": ["en_US.UTF-8", "en_US.utf8", "English_United States.1252"],
+    "fr_FR.UTF-8": ["fr_FR.UTF-8", "fr_FR.utf8", "French_France.1252"],
+    "ja_JP.UTF-8": ["ja_JP.UTF-8", "ja_JP.utf8", "Japanese_Japan.923"],
+    "ru_RU.UTF-8": ["ru_RU.UTF-8", "ru_RU.utf8", "Russian_Russia.1251"],
+    "zh_CN.UTF-8": ["zh_CN.UTF-8", "zh_CN.utf8", "Chinese_China.936"],
+    "fr_CA.ISO8859-1": ["fr_CA.ISO8859-1", "French_Canada.1252"],
+    "cs_CZ.ISO8859-2": ["cs_CZ.ISO8859-2", "Czech_Czech Republic.1250"],
 }
 for locale, alts in locales.items():
-  # Note: Using alts directly in the lambda body here will bind it to the value at the
-  # end of the loop. Assigning it to a default argument works around this issue.
-  DEFAULT_FEATURES.append(Feature(name='locale.{}'.format(locale),
-                                  when=lambda cfg, alts=alts: hasAnyLocale(cfg, alts)))
+    # Note: Using alts directly in the lambda body here will bind it to the value at the
+    # end of the loop. Assigning it to a default argument works around this issue.
+    DEFAULT_FEATURES.append(
+        Feature(
+            name="locale.{}".format(locale),
+            when=lambda cfg, alts=alts: hasAnyLocale(cfg, alts),
+        )
+    )
 
 
 # Add features representing the target platform name: darwin, linux, windows, etc...
 DEFAULT_FEATURES += [
-  Feature(name='darwin', when=lambda cfg: '__APPLE__' in compilerMacros(cfg)),
-  Feature(name='windows', when=lambda cfg: '_WIN32' in compilerMacros(cfg)),
-  Feature(name='windows-dll', when=lambda cfg: '_WIN32' in compilerMacros(cfg) and sourceBuilds(cfg, """
+    Feature(name="darwin", when=lambda cfg: "__APPLE__" in compilerMacros(cfg)),
+    Feature(name="windows", when=lambda cfg: "_WIN32" in compilerMacros(cfg)),
+    Feature(
+        name="windows-dll",
+        when=lambda cfg: "_WIN32" in compilerMacros(cfg)
+        and sourceBuilds(
+            cfg,
+            """
             #include <iostream>
             int main(int, char**) { return 0; }
-          """) and programSucceeds(cfg, """
+          """,
+        )
+        and programSucceeds(
+            cfg,
+            """
             #include <iostream>
             #include <windows.h>
             #include <winnt.h>
@@ -270,57 +411,76 @@
               // loaded from a DLL.
               return 0;
             }
-          """), actions=[AddCompileFlag('-DTEST_WINDOWS_DLL')]),
-  Feature(name='linux', when=lambda cfg: '__linux__' in compilerMacros(cfg)),
-  Feature(name='netbsd', when=lambda cfg: '__NetBSD__' in compilerMacros(cfg)),
-  Feature(name='freebsd', when=lambda cfg: '__FreeBSD__' in compilerMacros(cfg)),
-  Feature(name='LIBCXX-FREEBSD-FIXME', when=lambda cfg: '__FreeBSD__' in compilerMacros(cfg)),
+          """,
+        ),
+        actions=[AddCompileFlag("-DTEST_WINDOWS_DLL")],
+    ),
+    Feature(name="linux", when=lambda cfg: "__linux__" in compilerMacros(cfg)),
+    Feature(name="netbsd", when=lambda cfg: "__NetBSD__" in compilerMacros(cfg)),
+    Feature(name="freebsd", when=lambda cfg: "__FreeBSD__" in compilerMacros(cfg)),
+    Feature(
+        name="LIBCXX-FREEBSD-FIXME",
+        when=lambda cfg: "__FreeBSD__" in compilerMacros(cfg),
+    ),
 ]
 
 # Add features representing the build host platform name.
 # The build host could differ from the target platform for cross-compilation.
 DEFAULT_FEATURES += [
-  Feature(name='buildhost={}'.format(sys.platform.lower().strip())),
-  # sys.platform can often be represented by a "sub-system", such as 'win32', 'cygwin', 'mingw', freebsd13 & etc.
-  # We define a consolidated feature on a few platforms.
-  Feature(name='buildhost=windows', when=lambda cfg: platform.system().lower().startswith('windows')),
-  Feature(name='buildhost=freebsd', when=lambda cfg: platform.system().lower().startswith('freebsd')),
-  Feature(name='buildhost=aix', when=lambda cfg: platform.system().lower().startswith('aix'))
+    Feature(name="buildhost={}".format(sys.platform.lower().strip())),
+    # sys.platform can often be represented by a "sub-system", such as 'win32', 'cygwin', 'mingw', freebsd13 & etc.
+    # We define a consolidated feature on a few platforms.
+    Feature(
+        name="buildhost=windows",
+        when=lambda cfg: platform.system().lower().startswith("windows"),
+    ),
+    Feature(
+        name="buildhost=freebsd",
+        when=lambda cfg: platform.system().lower().startswith("freebsd"),
+    ),
+    Feature(
+        name="buildhost=aix",
+        when=lambda cfg: platform.system().lower().startswith("aix"),
+    ),
 ]
 
 # Detect whether GDB is on the system, has Python scripting and supports
 # adding breakpoint commands. If so add a substitution to access it.
 def check_gdb(cfg):
-  gdb_path = shutil.which('gdb')
-  if gdb_path is None:
-    return False
-
-  # Check that we can set breakpoint commands, which was added in 8.3.
-  # Using the quit command here means that gdb itself exits, not just
-  # the "python <...>" command.
-  test_src = """\
+    gdb_path = shutil.which("gdb")
+    if gdb_path is None:
+        return False
+
+    # Check that we can set breakpoint commands, which was added in 8.3.
+    # Using the quit command here means that gdb itself exits, not just
+    # the "python <...>" command.
+    test_src = """\
 try:
   gdb.Breakpoint(\"main\").commands=\"foo\"
 except AttributeError:
   gdb.execute(\"quit 1\")
 gdb.execute(\"quit\")"""
 
-  try:
-    stdout = subprocess.check_output(
-              [gdb_path, "-ex", "python " + test_src, "--batch"],
-              stderr=subprocess.DEVNULL, universal_newlines=True)
-  except subprocess.CalledProcessError:
-    # We can't set breakpoint commands
-    return False
+    try:
+        stdout = subprocess.check_output(
+            [gdb_path, "-ex", "python " + test_src, "--batch"],
+            stderr=subprocess.DEVNULL,
+            universal_newlines=True,
+        )
+    except subprocess.CalledProcessError:
+        # We can't set breakpoint commands
+        return False
+
+    # Check we actually ran the Python
+    return not "Python scripting is not supported" in stdout
 
-  # Check we actually ran the Python
-  return not "Python scripting is not supported" in stdout
 
 DEFAULT_FEATURES += [
-  Feature(name='host-has-gdb-with-python',
-    when=check_gdb,
-    actions=[AddSubstitution('%{gdb}', lambda cfg: shutil.which('gdb'))]
-  )
+    Feature(
+        name="host-has-gdb-with-python",
+        when=check_gdb,
+        actions=[AddSubstitution("%{gdb}", lambda cfg: shutil.which("gdb"))],
+    )
 ]
 
 # Define features for back-deployment testing.
@@ -337,48 +497,93 @@
 # be achieved by creating a `.verify.cpp` test that checks for the right errors, and
 # mark that test as requiring `stdlib=<vendor>-libc++ && target=<target>`.
 DEFAULT_FEATURES += [
-  # Tests that require std::to_chars(floating-point) in the built library
-  Feature(name='availability-fp_to_chars-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0|13.0)(.0)?}}', cfg.available_features)),
-
-  # Tests that require https://wg21.link/P0482 support in the built library
-  Feature(name='availability-char8_t_support-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0)(.0)?}}', cfg.available_features)),
-
-  # Tests that require __libcpp_verbose_abort support in the built library
-  Feature(name='availability-verbose_abort-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0|13.0)(.0)?}}', cfg.available_features)),
-
-  # Tests that require std::bad_variant_access in the built library
-  Feature(name='availability-bad_variant_access-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}', cfg.available_features)),
-
-  # Tests that require std::bad_optional_access in the built library
-  Feature(name='availability-bad_optional_access-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}', cfg.available_features)),
-
-  # Tests that require std::bad_any_cast in the built library
-  Feature(name='availability-bad_any_cast-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}', cfg.available_features)),
-
-  # Tests that require std::pmr support in the built library
-  Feature(name='availability-pmr-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0)(.0)?}}', cfg.available_features)),
-
-  # Tests that require std::filesystem support in the built library
-  Feature(name='availability-filesystem-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12|13|14)(.0)?}}', cfg.available_features)),
-
-  # Tests that require the C++20 synchronization library (P1135R6 implemented by https://llvm.org/D68480) in the built library
-  Feature(name='availability-synchronization_library-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12|13|14|15)(.0)?}}', cfg.available_features)),
-
-  # Tests that require support for std::shared_mutex and std::shared_timed_mutex in the built library
-  Feature(name='availability-shared_mutex-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11)(.0)?}}', cfg.available_features)),
-
-  # Tests that require support for aligned allocation in the built library. This is about `operator new(..., std::align_val_t, ...)` specifically,
-  # not other forms of aligned allocation.
-  Feature(name='availability-aligned_allocation-missing',
-    when=lambda cfg: BooleanExpression.evaluate('stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}', cfg.available_features)),
+    # Tests that require std::to_chars(floating-point) in the built library
+    Feature(
+        name="availability-fp_to_chars-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0|13.0)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require https://wg21.link/P0482 support in the built library
+    Feature(
+        name="availability-char8_t_support-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require __libcpp_verbose_abort support in the built library
+    Feature(
+        name="availability-verbose_abort-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0|13.0)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require std::bad_variant_access in the built library
+    Feature(
+        name="availability-bad_variant_access-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require std::bad_optional_access in the built library
+    Feature(
+        name="availability-bad_optional_access-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require std::bad_any_cast in the built library
+    Feature(
+        name="availability-bad_any_cast-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require std::pmr support in the built library
+    Feature(
+        name="availability-pmr-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx{{(10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require std::filesystem support in the built library
+    Feature(
+        name="availability-filesystem-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12|13|14)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require the C++20 synchronization library (P1135R6 implemented by https://llvm.org/D68480) in the built library
+    Feature(
+        name="availability-synchronization_library-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12|13|14|15)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require support for std::shared_mutex and std::shared_timed_mutex in the built library
+    Feature(
+        name="availability-shared_mutex-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
+    # Tests that require support for aligned allocation in the built library. This is about `operator new(..., std::align_val_t, ...)` specifically,
+    # not other forms of aligned allocation.
+    Feature(
+        name="availability-aligned_allocation-missing",
+        when=lambda cfg: BooleanExpression.evaluate(
+            "stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{(9|10|11|12)(.0)?}}",
+            cfg.available_features,
+        ),
+    ),
 ]
diff --git a/libcxx/utils/libcxx/test/format.py b/libcxx/utils/libcxx/test/format.py
--- a/libcxx/utils/libcxx/test/format.py
+++ b/libcxx/utils/libcxx/test/format.py
@@ -1,10 +1,10 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 import lit
 import lit.formats
@@ -13,6 +13,7 @@
 import re
 import shutil
 
+
 def _getTempPaths(test):
     """
     Return the values to use for the %T and %t substitutions, respectively.
@@ -22,15 +23,17 @@
     """
     tmpDir, _ = lit.TestRunner.getTempPaths(test)
     _, testName = os.path.split(test.getExecPath())
-    tmpDir = os.path.join(tmpDir, testName + '.dir')
-    tmpBase = os.path.join(tmpDir, 't')
+    tmpDir = os.path.join(tmpDir, testName + ".dir")
+    tmpBase = os.path.join(tmpDir, "t")
     return tmpDir, tmpBase
 
+
 def _checkBaseSubstitutions(substitutions):
     substitutions = [s for (s, _) in substitutions]
-    for s in ['%{cxx}', '%{compile_flags}', '%{link_flags}', '%{flags}', '%{exec}']:
+    for s in ["%{cxx}", "%{compile_flags}", "%{link_flags}", "%{flags}", "%{exec}"]:
         assert s in substitutions, "Required substitution {} was not provided".format(s)
 
+
 def parseScript(test, preamble):
     """
     Extract the script from a test, with substitutions applied.
@@ -52,32 +55,41 @@
 
     # Check base substitutions and add the %{build} and %{run} convenience substitutions
     _checkBaseSubstitutions(substitutions)
-    substitutions.append(('%{build}', '%{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe'))
-    substitutions.append(('%{run}', '%{exec} %t.exe'))
+    substitutions.append(
+        ("%{build}", "%{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe")
+    )
+    substitutions.append(("%{run}", "%{exec} %t.exe"))
 
     # Parse the test file, including custom directives
     additionalCompileFlags = []
     fileDependencies = []
     parsers = [
-        lit.TestRunner.IntegratedTestKeywordParser('FILE_DEPENDENCIES:',
-                                                   lit.TestRunner.ParserKind.LIST,
-                                                   initial_value=fileDependencies),
-        lit.TestRunner.IntegratedTestKeywordParser('ADDITIONAL_COMPILE_FLAGS:',
-                                                   lit.TestRunner.ParserKind.LIST,
-                                                   initial_value=additionalCompileFlags)
+        lit.TestRunner.IntegratedTestKeywordParser(
+            "FILE_DEPENDENCIES:",
+            lit.TestRunner.ParserKind.LIST,
+            initial_value=fileDependencies,
+        ),
+        lit.TestRunner.IntegratedTestKeywordParser(
+            "ADDITIONAL_COMPILE_FLAGS:",
+            lit.TestRunner.ParserKind.LIST,
+            initial_value=additionalCompileFlags,
+        ),
     ]
 
     # Add conditional parsers for ADDITIONAL_COMPILE_FLAGS. This should be replaced by first
     # class support for conditional keywords in Lit, which would allow evaluating arbitrary
     # Lit boolean expressions instead.
     for feature in test.config.available_features:
-        parser = lit.TestRunner.IntegratedTestKeywordParser('ADDITIONAL_COMPILE_FLAGS({}):'.format(feature),
-                                                            lit.TestRunner.ParserKind.LIST,
-                                                            initial_value=additionalCompileFlags)
+        parser = lit.TestRunner.IntegratedTestKeywordParser(
+            "ADDITIONAL_COMPILE_FLAGS({}):".format(feature),
+            lit.TestRunner.ParserKind.LIST,
+            initial_value=additionalCompileFlags,
+        )
         parsers.append(parser)
 
-    scriptInTest = lit.TestRunner.parseIntegratedTestScript(test, additional_parsers=parsers,
-                                                            require_script=not preamble)
+    scriptInTest = lit.TestRunner.parseIntegratedTestScript(
+        test, additional_parsers=parsers, require_script=not preamble
+    )
     if isinstance(scriptInTest, lit.Test.Result):
         return scriptInTest
 
@@ -87,17 +99,22 @@
     # that file to the execution directory. Execute the copy from %S to allow
     # relative paths from the test directory.
     for dep in fileDependencies:
-        script += ['%dbg(SETUP) cd %S && cp {} %T'.format(dep)]
+        script += ["%dbg(SETUP) cd %S && cp {} %T".format(dep)]
     script += preamble
     script += scriptInTest
 
     # Add compile flags specified with ADDITIONAL_COMPILE_FLAGS.
-    substitutions = [(s, x + ' ' + ' '.join(additionalCompileFlags)) if s == '%{compile_flags}'
-                            else (s, x) for (s, x) in substitutions]
+    substitutions = [
+        (s, x + " " + " ".join(additionalCompileFlags))
+        if s == "%{compile_flags}"
+        else (s, x)
+        for (s, x) in substitutions
+    ]
 
     # Perform substitutions in the script itself.
-    script = lit.TestRunner.applySubstitutions(script, substitutions,
-                                               recursion_limit=test.config.recursiveExpansionLimit)
+    script = lit.TestRunner.applySubstitutions(
+        script, substitutions, recursion_limit=test.config.recursiveExpansionLimit
+    )
 
     return script
 
@@ -187,80 +204,100 @@
             Equivalent to `%{exec} %t.exe`. This is intended to be used
             in conjunction with the %{build} substitution.
     """
+
     def getTestsInDirectory(self, testSuite, pathInSuite, litConfig, localConfig):
-        SUPPORTED_SUFFIXES = ['[.]pass[.]cpp$', '[.]pass[.]mm$',
-                              '[.]compile[.]pass[.]cpp$', '[.]compile[.]pass[.]mm$',
-                              '[.]compile[.]fail[.]cpp$',
-                              '[.]link[.]pass[.]cpp$', '[.]link[.]pass[.]mm$',
-                              '[.]link[.]fail[.]cpp$',
-                              '[.]sh[.][^.]+$',
-                              '[.]verify[.]cpp$',
-                              '[.]fail[.]cpp$']
+        SUPPORTED_SUFFIXES = [
+            "[.]pass[.]cpp$",
+            "[.]pass[.]mm$",
+            "[.]compile[.]pass[.]cpp$",
+            "[.]compile[.]pass[.]mm$",
+            "[.]compile[.]fail[.]cpp$",
+            "[.]link[.]pass[.]cpp$",
+            "[.]link[.]pass[.]mm$",
+            "[.]link[.]fail[.]cpp$",
+            "[.]sh[.][^.]+$",
+            "[.]verify[.]cpp$",
+            "[.]fail[.]cpp$",
+        ]
         sourcePath = testSuite.getSourcePath(pathInSuite)
         for filename in os.listdir(sourcePath):
             # Ignore dot files and excluded tests.
-            if filename.startswith('.') or filename in localConfig.excludes:
+            if filename.startswith(".") or filename in localConfig.excludes:
                 continue
 
             filepath = os.path.join(sourcePath, filename)
             if not os.path.isdir(filepath):
                 if any([re.search(ext, filename) for ext in SUPPORTED_SUFFIXES]):
-                    yield lit.Test.Test(testSuite, pathInSuite + (filename,), localConfig)
+                    yield lit.Test.Test(
+                        testSuite, pathInSuite + (filename,), localConfig
+                    )
 
     def execute(self, test, litConfig):
-        VERIFY_FLAGS = '-Xclang -verify -Xclang -verify-ignore-unexpected=note -ferror-limit=0'
-        supportsVerify = 'verify-support' in test.config.available_features
+        VERIFY_FLAGS = (
+            "-Xclang -verify -Xclang -verify-ignore-unexpected=note -ferror-limit=0"
+        )
+        supportsVerify = "verify-support" in test.config.available_features
         filename = test.path_in_suite[-1]
 
-        if re.search('[.]sh[.][^.]+$', filename):
-            steps = [ ] # The steps are already in the script
+        if re.search("[.]sh[.][^.]+$", filename):
+            steps = []  # The steps are already in the script
             return self._executeShTest(test, litConfig, steps)
-        elif filename.endswith('.compile.pass.cpp') or filename.endswith('.compile.pass.mm'):
+        elif filename.endswith(".compile.pass.cpp") or filename.endswith(
+            ".compile.pass.mm"
+        ):
             steps = [
                 "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} -fsyntax-only"
             ]
             return self._executeShTest(test, litConfig, steps)
-        elif filename.endswith('.compile.fail.cpp'):
+        elif filename.endswith(".compile.fail.cpp"):
             steps = [
                 "%dbg(COMPILED WITH) ! %{cxx} %s %{flags} %{compile_flags} -fsyntax-only"
             ]
             return self._executeShTest(test, litConfig, steps)
-        elif filename.endswith('.link.pass.cpp') or filename.endswith('.link.pass.mm'):
+        elif filename.endswith(".link.pass.cpp") or filename.endswith(".link.pass.mm"):
             steps = [
                 "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe"
             ]
             return self._executeShTest(test, litConfig, steps)
-        elif filename.endswith('.link.fail.cpp'):
+        elif filename.endswith(".link.fail.cpp"):
             steps = [
                 "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} -c -o %t.o",
-                "%dbg(LINKED WITH) ! %{cxx} %t.o %{flags} %{link_flags} -o %t.exe"
+                "%dbg(LINKED WITH) ! %{cxx} %t.o %{flags} %{link_flags} -o %t.exe",
             ]
             return self._executeShTest(test, litConfig, steps)
-        elif filename.endswith('.verify.cpp'):
+        elif filename.endswith(".verify.cpp"):
             if not supportsVerify:
-                return lit.Test.Result(lit.Test.UNSUPPORTED,
-                    "Test {} requires support for Clang-verify, which isn't supported by the compiler".format(test.getFullName()))
+                return lit.Test.Result(
+                    lit.Test.UNSUPPORTED,
+                    "Test {} requires support for Clang-verify, which isn't supported by the compiler".format(
+                        test.getFullName()
+                    ),
+                )
             steps = [
                 # Note: Use -Wno-error to make sure all diagnostics are not treated as errors,
                 #       which doesn't make sense for clang-verify tests.
-                "%dbg(COMPILED WITH) %{{cxx}} %s %{{flags}} %{{compile_flags}} -fsyntax-only -Wno-error {}".format(VERIFY_FLAGS)
+                "%dbg(COMPILED WITH) %{{cxx}} %s %{{flags}} %{{compile_flags}} -fsyntax-only -Wno-error {}".format(
+                    VERIFY_FLAGS
+                )
             ]
             return self._executeShTest(test, litConfig, steps)
         # Make sure to check these ones last, since they will match other
         # suffixes above too.
-        elif filename.endswith('.pass.cpp') or filename.endswith('.pass.mm'):
+        elif filename.endswith(".pass.cpp") or filename.endswith(".pass.mm"):
             steps = [
                 "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe",
-                "%dbg(EXECUTED AS) %{exec} %t.exe"
+                "%dbg(EXECUTED AS) %{exec} %t.exe",
             ]
             return self._executeShTest(test, litConfig, steps)
         # This is like a .verify.cpp test when clang-verify is supported,
         # otherwise it's like a .compile.fail.cpp test. This is only provided
         # for backwards compatibility with the test suite.
-        elif filename.endswith('.fail.cpp'):
+        elif filename.endswith(".fail.cpp"):
             if supportsVerify:
                 steps = [
-                    "%dbg(COMPILED WITH) %{{cxx}} %s %{{flags}} %{{compile_flags}} -fsyntax-only -Wno-error {}".format(VERIFY_FLAGS)
+                    "%dbg(COMPILED WITH) %{{cxx}} %s %{{flags}} %{{compile_flags}} -fsyntax-only -Wno-error {}".format(
+                        VERIFY_FLAGS
+                    )
                 ]
             else:
                 steps = [
@@ -268,19 +305,25 @@
                 ]
             return self._executeShTest(test, litConfig, steps)
         else:
-            return lit.Test.Result(lit.Test.UNRESOLVED, "Unknown test suffix for '{}'".format(filename))
+            return lit.Test.Result(
+                lit.Test.UNRESOLVED, "Unknown test suffix for '{}'".format(filename)
+            )
 
     def _executeShTest(self, test, litConfig, steps):
         if test.config.unsupported:
-            return lit.Test.Result(lit.Test.UNSUPPORTED, 'Test is unsupported')
+            return lit.Test.Result(lit.Test.UNSUPPORTED, "Test is unsupported")
 
         script = parseScript(test, steps)
         if isinstance(script, lit.Test.Result):
             return script
 
         if litConfig.noExecute:
-            return lit.Test.Result(lit.Test.XFAIL if test.isExpectedToFail() else lit.Test.PASS)
+            return lit.Test.Result(
+                lit.Test.XFAIL if test.isExpectedToFail() else lit.Test.PASS
+            )
         else:
             _, tmpBase = _getTempPaths(test)
             useExternalSh = False
-            return lit.TestRunner._runShTest(test, litConfig, useExternalSh, script, tmpBase)
+            return lit.TestRunner._runShTest(
+                test, litConfig, useExternalSh, script, tmpBase
+            )
diff --git a/libcxx/utils/libcxx/test/googlebenchmark.py b/libcxx/utils/libcxx/test/googlebenchmark.py
--- a/libcxx/utils/libcxx/test/googlebenchmark.py
+++ b/libcxx/utils/libcxx/test/googlebenchmark.py
@@ -8,20 +8,21 @@
 import lit.util
 from lit.formats.base import TestFormat
 
-kIsWindows = sys.platform in ['win32', 'cygwin']
+kIsWindows = sys.platform in ["win32", "cygwin"]
+
 
 class GoogleBenchmark(TestFormat):
     def __init__(self, test_sub_dirs, test_suffix, benchmark_args=[]):
         self.benchmark_args = list(benchmark_args)
-        self.test_sub_dirs = os.path.normcase(str(test_sub_dirs)).split(';')
+        self.test_sub_dirs = os.path.normcase(str(test_sub_dirs)).split(";")
 
         # On Windows, assume tests will also end in '.exe'.
         exe_suffix = str(test_suffix)
         if kIsWindows:
-            exe_suffix += '.exe'
+            exe_suffix += ".exe"
 
         # Also check for .py files for testing purposes.
-        self.test_suffixes = {exe_suffix, test_suffix + '.py'}
+        self.test_suffixes = {exe_suffix, test_suffix + ".py"}
 
     def getBenchmarkTests(self, path, litConfig, localConfig):
         """getBenchmarkTests(path) - [name]
@@ -36,14 +37,14 @@
         # TODO: allow splitting tests according to the "benchmark family" so
         # the output for a single family of tests all belongs to the same test
         # target.
-        list_test_cmd = [path, '--benchmark_list_tests']
+        list_test_cmd = [path, "--benchmark_list_tests"]
         try:
-            output = subprocess.check_output(list_test_cmd,
-                                             env=localConfig.environment)
+            output = subprocess.check_output(list_test_cmd, env=localConfig.environment)
         except subprocess.CalledProcessError as exc:
             litConfig.warning(
                 "unable to discover google-benchmarks in %r: %s. Process output: %s"
-                % (path, sys.exc_info()[1], exc.output))
+                % (path, sys.exc_info()[1], exc.output)
+            )
             raise StopIteration
 
         nested_tests = []
@@ -53,69 +54,72 @@
                 continue
 
             index = 0
-            while ln[index*2:index*2+2] == '  ':
+            while ln[index * 2 : index * 2 + 2] == "  ":
                 index += 1
             while len(nested_tests) > index:
                 nested_tests.pop()
 
-            ln = ln[index*2:]
-            if ln.endswith('.'):
+            ln = ln[index * 2 :]
+            if ln.endswith("."):
                 nested_tests.append(ln)
-            elif any([name.startswith('DISABLED_')
-                      for name in nested_tests + [ln]]):
+            elif any([name.startswith("DISABLED_") for name in nested_tests + [ln]]):
                 # Gtest will internally skip these tests. No need to launch a
                 # child process for it.
                 continue
             else:
-                yield ''.join(nested_tests) + ln
+                yield "".join(nested_tests) + ln
 
-    def getTestsInDirectory(self, testSuite, path_in_suite,
-                            litConfig, localConfig):
+    def getTestsInDirectory(self, testSuite, path_in_suite, litConfig, localConfig):
         source_path = testSuite.getSourcePath(path_in_suite)
         for subdir in self.test_sub_dirs:
             dir_path = os.path.join(source_path, subdir)
             if not os.path.isdir(dir_path):
                 continue
-            for fn in lit.util.listdir_files(dir_path,
-                                             suffixes=self.test_suffixes):
+            for fn in lit.util.listdir_files(dir_path, suffixes=self.test_suffixes):
                 # Discover the tests in this executable.
                 execpath = os.path.join(source_path, subdir, fn)
                 testnames = self.getBenchmarkTests(execpath, litConfig, localConfig)
                 for testname in testnames:
                     testPath = path_in_suite + (subdir, fn, testname)
-                    yield lit.Test.Test(testSuite, testPath, localConfig,
-                                        file_path=execpath)
+                    yield lit.Test.Test(
+                        testSuite, testPath, localConfig, file_path=execpath
+                    )
 
     def execute(self, test, litConfig):
-        testPath,testName = os.path.split(test.getSourcePath())
+        testPath, testName = os.path.split(test.getSourcePath())
         while not os.path.exists(testPath):
             # Handle GTest parametrized and typed tests, whose name includes
             # some '/'s.
             testPath, namePrefix = os.path.split(testPath)
-            testName = namePrefix + '/' + testName
+            testName = namePrefix + "/" + testName
 
-        cmd = [testPath, '--benchmark_filter=%s$' % testName ] + self.benchmark_args
+        cmd = [testPath, "--benchmark_filter=%s$" % testName] + self.benchmark_args
 
         if litConfig.noExecute:
-            return lit.Test.PASS, ''
+            return lit.Test.PASS, ""
 
         try:
             out, err, exitCode = lit.util.executeCommand(
-                cmd, env=test.config.environment,
-                timeout=litConfig.maxIndividualTestTime)
+                cmd,
+                env=test.config.environment,
+                timeout=litConfig.maxIndividualTestTime,
+            )
         except lit.util.ExecuteCommandTimeoutException:
-            return (lit.Test.TIMEOUT,
-                    'Reached timeout of {} seconds'.format(
-                        litConfig.maxIndividualTestTime)
-                   )
+            return (
+                lit.Test.TIMEOUT,
+                "Reached timeout of {} seconds".format(litConfig.maxIndividualTestTime),
+            )
 
         if exitCode:
-            return lit.Test.FAIL, ('exit code: %d\n' % exitCode) + out + err
+            return lit.Test.FAIL, ("exit code: %d\n" % exitCode) + out + err
 
         passing_test_line = testName
         if passing_test_line not in out:
-            msg = ('Unable to find %r in google benchmark output:\n\n%s%s' %
-                   (passing_test_line, out, err))
+            msg = "Unable to find %r in google benchmark output:\n\n%s%s" % (
+                passing_test_line,
+                out,
+                err,
+            )
             return lit.Test.UNRESOLVED, msg
 
         return lit.Test.PASS, err + out
diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -1,122 +1,154 @@
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 from libcxx.test.dsl import *
 from libcxx.test.features import _isMSVC
 import re
 
 _warningFlags = [
-  '-Werror',
-  '-Wall',
-  '-Wctad-maybe-unsupported',
-  '-Wextra',
-  '-Wshadow',
-  '-Wundef',
-  '-Wunused-template',
-  '-Wno-unused-command-line-argument',
-  '-Wno-attributes',
-  '-Wno-pessimizing-move',
-  '-Wno-c++11-extensions',
-  '-Wno-noexcept-type',
-  '-Wno-aligned-allocation-unavailable',
-  '-Wno-atomic-alignment',
-
-  # GCC warns about places where we might want to add sized allocation/deallocation
-  # functions, but we know better what we're doing/testing in the test suite.
-  '-Wno-sized-deallocation',
-
-  # Turn off warnings about user-defined literals with reserved suffixes. Those are
-  # just noise since we are testing the Standard Library itself.
-  '-Wno-literal-suffix', # GCC
-  '-Wno-user-defined-literals', # Clang
-
-  # GCC warns about this when TEST_IS_CONSTANT_EVALUATED is used on a non-constexpr
-  # function. (This mostely happens in C++11 mode.)
-  # TODO(mordante) investigate a solution for this issue.
-  '-Wno-tautological-compare',
-
-  # -Wstringop-overread and -Wstringop-overflow seem to be a bit buggy currently
-  '-Wno-stringop-overread',
-  '-Wno-stringop-overflow',
-
-  # These warnings should be enabled in order to support the MSVC
-  # team using the test suite; They enable the warnings below and
-  # expect the test suite to be clean.
-  '-Wsign-compare',
-  '-Wunused-variable',
-  '-Wunused-parameter',
-  '-Wunreachable-code',
-  '-Wno-unused-local-typedef',
+    "-Werror",
+    "-Wall",
+    "-Wctad-maybe-unsupported",
+    "-Wextra",
+    "-Wshadow",
+    "-Wundef",
+    "-Wunused-template",
+    "-Wno-unused-command-line-argument",
+    "-Wno-attributes",
+    "-Wno-pessimizing-move",
+    "-Wno-c++11-extensions",
+    "-Wno-noexcept-type",
+    "-Wno-aligned-allocation-unavailable",
+    "-Wno-atomic-alignment",
+    # GCC warns about places where we might want to add sized allocation/deallocation
+    # functions, but we know better what we're doing/testing in the test suite.
+    "-Wno-sized-deallocation",
+    # Turn off warnings about user-defined literals with reserved suffixes. Those are
+    # just noise since we are testing the Standard Library itself.
+    "-Wno-literal-suffix",  # GCC
+    "-Wno-user-defined-literals",  # Clang
+    # GCC warns about this when TEST_IS_CONSTANT_EVALUATED is used on a non-constexpr
+    # function. (This mostely happens in C++11 mode.)
+    # TODO(mordante) investigate a solution for this issue.
+    "-Wno-tautological-compare",
+    # -Wstringop-overread and -Wstringop-overflow seem to be a bit buggy currently
+    "-Wno-stringop-overread",
+    "-Wno-stringop-overflow",
+    # These warnings should be enabled in order to support the MSVC
+    # team using the test suite; They enable the warnings below and
+    # expect the test suite to be clean.
+    "-Wsign-compare",
+    "-Wunused-variable",
+    "-Wunused-parameter",
+    "-Wunreachable-code",
+    "-Wno-unused-local-typedef",
 ]
 
-_allStandards = ['c++03', 'c++11', 'c++14', 'c++17', 'c++20', 'c++2b']
-def getStdFlag(cfg, std):
-  fallbacks = {
-    'c++11': 'c++0x',
-    'c++14': 'c++1y',
-    'c++17': 'c++1z',
-    'c++20': 'c++2a',
-  }
-  if hasCompileFlag(cfg, '-std='+std):
-    return '-std='+std
-  if std in fallbacks and hasCompileFlag(cfg, '-std='+fallbacks[std]):
-    return '-std='+fallbacks[std]
-  return None
+_allStandards = ["c++03", "c++11", "c++14", "c++17", "c++20", "c++2b"]
 
-DEFAULT_PARAMETERS = [
-  Parameter(name='target_triple', type=str,
-            help="The target triple to compile the test suite for. This must be "
-                 "compatible with the target that the tests will be run on.",
-            actions=lambda triple: filter(None, [
-              AddFeature('target={}'.format(triple)),
-              AddFlagIfSupported('--target={}'.format(triple)),
-              AddSubstitution('%{triple}', triple)
-            ])),
 
-  Parameter(name='std', choices=_allStandards, type=str,
-            help="The version of the standard to compile the test suite with.",
-            default=lambda cfg: next(s for s in reversed(_allStandards) if getStdFlag(cfg, s)),
-            actions=lambda std: [
-              AddFeature(std),
-              AddSubstitution('%{cxx_std}', re.sub('\+','x', std)),
-              AddCompileFlag(lambda cfg: getStdFlag(cfg, std)),
-            ]),
-
-  Parameter(name='enable_modules', choices=[True, False], type=bool, default=False,
-            help="Whether to build the test suite with Clang modules enabled.",
-            actions=lambda modules: [
-              AddFeature('modules-build'),
-              AddCompileFlag('-fmodules'),
-              AddCompileFlag('-fcxx-modules'), # AppleClang disregards -fmodules entirely when compiling C++. This enables modules for C++.
-            ] if modules else []),
-
-  Parameter(name='enable_modules_lsv', choices=[True, False], type=bool, default=False,
-          help="Whether to enable Local Submodule Visibility in the Modules build.",
-          actions=lambda lsv: [
-            AddCompileFlag('-Xclang -fmodules-local-submodule-visibility'),
-          ] if lsv else []),
-
-  Parameter(name='enable_exceptions', choices=[True, False], type=bool, default=True,
-            help="Whether to enable exceptions when compiling the test suite.",
-            actions=lambda exceptions: [] if exceptions else [
-              AddFeature('no-exceptions'),
-              AddCompileFlag('-fno-exceptions')
-            ]),
+def getStdFlag(cfg, std):
+    fallbacks = {
+        "c++11": "c++0x",
+        "c++14": "c++1y",
+        "c++17": "c++1z",
+        "c++20": "c++2a",
+    }
+    if hasCompileFlag(cfg, "-std=" + std):
+        return "-std=" + std
+    if std in fallbacks and hasCompileFlag(cfg, "-std=" + fallbacks[std]):
+        return "-std=" + fallbacks[std]
+    return None
 
-  Parameter(name='enable_rtti', choices=[True, False], type=bool, default=True,
-            help="Whether to enable RTTI when compiling the test suite.",
-            actions=lambda rtti: [] if rtti else [
-              AddFeature('no-rtti'),
-              AddCompileFlag('-fno-rtti')
-            ]),
 
-  Parameter(name='stdlib', choices=['llvm-libc++', 'apple-libc++', 'libstdc++', 'msvc'], type=str, default='llvm-libc++',
-            help="""The C++ Standard Library implementation being tested.
+DEFAULT_PARAMETERS = [
+    Parameter(
+        name="target_triple",
+        type=str,
+        help="The target triple to compile the test suite for. This must be "
+        "compatible with the target that the tests will be run on.",
+        actions=lambda triple: filter(
+            None,
+            [
+                AddFeature("target={}".format(triple)),
+                AddFlagIfSupported("--target={}".format(triple)),
+                AddSubstitution("%{triple}", triple),
+            ],
+        ),
+    ),
+    Parameter(
+        name="std",
+        choices=_allStandards,
+        type=str,
+        help="The version of the standard to compile the test suite with.",
+        default=lambda cfg: next(
+            s for s in reversed(_allStandards) if getStdFlag(cfg, s)
+        ),
+        actions=lambda std: [
+            AddFeature(std),
+            AddSubstitution("%{cxx_std}", re.sub("\+", "x", std)),
+            AddCompileFlag(lambda cfg: getStdFlag(cfg, std)),
+        ],
+    ),
+    Parameter(
+        name="enable_modules",
+        choices=[True, False],
+        type=bool,
+        default=False,
+        help="Whether to build the test suite with Clang modules enabled.",
+        actions=lambda modules: [
+            AddFeature("modules-build"),
+            AddCompileFlag("-fmodules"),
+            AddCompileFlag(
+                "-fcxx-modules"
+            ),  # AppleClang disregards -fmodules entirely when compiling C++. This enables modules for C++.
+        ]
+        if modules
+        else [],
+    ),
+    Parameter(
+        name="enable_modules_lsv",
+        choices=[True, False],
+        type=bool,
+        default=False,
+        help="Whether to enable Local Submodule Visibility in the Modules build.",
+        actions=lambda lsv: [
+            AddCompileFlag("-Xclang -fmodules-local-submodule-visibility"),
+        ]
+        if lsv
+        else [],
+    ),
+    Parameter(
+        name="enable_exceptions",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable exceptions when compiling the test suite.",
+        actions=lambda exceptions: []
+        if exceptions
+        else [AddFeature("no-exceptions"), AddCompileFlag("-fno-exceptions")],
+    ),
+    Parameter(
+        name="enable_rtti",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable RTTI when compiling the test suite.",
+        actions=lambda rtti: []
+        if rtti
+        else [AddFeature("no-rtti"), AddCompileFlag("-fno-rtti")],
+    ),
+    Parameter(
+        name="stdlib",
+        choices=["llvm-libc++", "apple-libc++", "libstdc++", "msvc"],
+        type=str,
+        default="llvm-libc++",
+        help="""The C++ Standard Library implementation being tested.
 
                  Note that this parameter can also be used to encode different 'flavors' of the same
                  standard library, such as libc++ as shipped by a different vendor, if it has different
@@ -130,89 +162,149 @@
                  - libstdc++: The GNU C++ library typically shipped with GCC.
                  - msvc: The Microsoft implementation of the C++ Standard Library.
                 """,
-            actions=lambda stdlib: filter(None, [
-              AddFeature('stdlib={}'.format(stdlib)),
-              # Also add an umbrella feature 'stdlib=libc++' for all flavors of libc++, to simplify
-              # the test suite.
-              AddFeature('stdlib=libc++') if re.match('.+-libc\+\+', stdlib) else None
-            ])),
-
-  Parameter(name='enable_warnings', choices=[True, False], type=bool, default=True,
-            help="Whether to enable warnings when compiling the test suite.",
-            actions=lambda warnings: [] if not warnings else
-              [AddOptionalWarningFlag(w) for w in _warningFlags] +
-              [AddCompileFlag('-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER')]
+        actions=lambda stdlib: filter(
+            None,
+            [
+                AddFeature("stdlib={}".format(stdlib)),
+                # Also add an umbrella feature 'stdlib=libc++' for all flavors of libc++, to simplify
+                # the test suite.
+                AddFeature("stdlib=libc++")
+                if re.match(".+-libc\+\+", stdlib)
+                else None,
+            ],
+        ),
+    ),
+    Parameter(
+        name="enable_warnings",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable warnings when compiling the test suite.",
+        actions=lambda warnings: []
+        if not warnings
+        else [AddOptionalWarningFlag(w) for w in _warningFlags]
+        + [AddCompileFlag("-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER")],
+    ),
+    Parameter(
+        name="use_sanitizer",
+        choices=[
+            "",
+            "Address",
+            "HWAddress",
+            "Undefined",
+            "Memory",
+            "MemoryWithOrigins",
+            "Thread",
+            "DataFlow",
+            "Leaks",
+        ],
+        type=str,
+        default="",
+        help="An optional sanitizer to enable when building and running the test suite.",
+        actions=lambda sanitizer: filter(
+            None,
+            [
+                AddFlag("-g -fno-omit-frame-pointer") if sanitizer else None,
+                AddFlag(
+                    "-fsanitize=undefined -fno-sanitize=float-divide-by-zero -fno-sanitize-recover=all"
+                )
+                if sanitizer == "Undefined"
+                else None,
+                AddFeature("ubsan") if sanitizer == "Undefined" else None,
+                AddFlag("-fsanitize=address") if sanitizer == "Address" else None,
+                AddFeature("asan") if sanitizer == "Address" else None,
+                AddFlag("-fsanitize=hwaddress") if sanitizer == "HWAddress" else None,
+                AddFeature("hwasan") if sanitizer == "HWAddress" else None,
+                AddFlag("-fsanitize=memory")
+                if sanitizer in ["Memory", "MemoryWithOrigins"]
+                else None,
+                AddFeature("msan")
+                if sanitizer in ["Memory", "MemoryWithOrigins"]
+                else None,
+                AddFlag("-fsanitize-memory-track-origins")
+                if sanitizer == "MemoryWithOrigins"
+                else None,
+                AddFlag("-fsanitize=thread") if sanitizer == "Thread" else None,
+                AddFeature("tsan") if sanitizer == "Thread" else None,
+                AddFlag("-fsanitize=dataflow") if sanitizer == "DataFlow" else None,
+                AddFlag("-fsanitize=leaks") if sanitizer == "Leaks" else None,
+                AddFeature("sanitizer-new-delete")
+                if sanitizer
+                in ["Address", "HWAddress", "Memory", "MemoryWithOrigins", "Thread"]
+                else None,
+            ],
+        ),
+    ),
+    Parameter(
+        name="enable_experimental",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable tests for experimental C++ Library features.",
+        actions=lambda experimental: [
+            # When linking in MSVC mode via the Clang driver, a -l<foo>
+            # maps to <foo>.lib, so we need to use -llibc++experimental here
+            # to make it link against the static libc++experimental.lib.
+            # We can't check for the feature 'msvc' in available_features
+            # as those features are added after processing parameters.
+            AddFeature("c++experimental"),
+            PrependLinkFlag(
+                lambda cfg: "-llibc++experimental"
+                if _isMSVC(cfg)
+                else "-lc++experimental"
             ),
-
-  Parameter(name='use_sanitizer', choices=['', 'Address', 'HWAddress', 'Undefined', 'Memory', 'MemoryWithOrigins', 'Thread', 'DataFlow', 'Leaks'], type=str, default='',
-            help="An optional sanitizer to enable when building and running the test suite.",
-            actions=lambda sanitizer: filter(None, [
-              AddFlag('-g -fno-omit-frame-pointer') if sanitizer else None,
-
-              AddFlag('-fsanitize=undefined -fno-sanitize=float-divide-by-zero -fno-sanitize-recover=all') if sanitizer == 'Undefined' else None,
-              AddFeature('ubsan')                                                                          if sanitizer == 'Undefined' else None,
-
-              AddFlag('-fsanitize=address') if sanitizer == 'Address' else None,
-              AddFeature('asan')            if sanitizer == 'Address' else None,
-
-              AddFlag('-fsanitize=hwaddress') if sanitizer == 'HWAddress' else None,
-              AddFeature('hwasan')            if sanitizer == 'HWAddress' else None,
-
-              AddFlag('-fsanitize=memory')               if sanitizer in ['Memory', 'MemoryWithOrigins'] else None,
-              AddFeature('msan')                         if sanitizer in ['Memory', 'MemoryWithOrigins'] else None,
-              AddFlag('-fsanitize-memory-track-origins') if sanitizer == 'MemoryWithOrigins' else None,
-
-              AddFlag('-fsanitize=thread') if sanitizer == 'Thread' else None,
-              AddFeature('tsan')           if sanitizer == 'Thread' else None,
-
-              AddFlag('-fsanitize=dataflow') if sanitizer == 'DataFlow' else None,
-              AddFlag('-fsanitize=leaks') if sanitizer == 'Leaks' else None,
-
-              AddFeature('sanitizer-new-delete') if sanitizer in ['Address', 'HWAddress', 'Memory', 'MemoryWithOrigins', 'Thread'] else None,
-            ])),
-
-  Parameter(name='enable_experimental', choices=[True, False], type=bool, default=True,
-            help="Whether to enable tests for experimental C++ Library features.",
-            actions=lambda experimental: [
-              # When linking in MSVC mode via the Clang driver, a -l<foo>
-              # maps to <foo>.lib, so we need to use -llibc++experimental here
-              # to make it link against the static libc++experimental.lib.
-              # We can't check for the feature 'msvc' in available_features
-              # as those features are added after processing parameters.
-              AddFeature('c++experimental'),
-              PrependLinkFlag(lambda cfg: '-llibc++experimental' if _isMSVC(cfg) else '-lc++experimental'),
-              AddCompileFlag('-D_LIBCPP_ENABLE_EXPERIMENTAL'),
-            ] if experimental else [
-              AddFeature('libcpp-has-no-incomplete-format'),
-              AddFeature('libcpp-has-no-incomplete-pstl'),
-            ]),
-
-  Parameter(name='long_tests', choices=[True, False], type=bool, default=True,
-            help="Whether to enable tests that take longer to run. This can be useful when running on a very slow device.",
-            actions=lambda enabled: [] if not enabled else [
-              AddFeature('long_tests')
-            ]),
-
-  Parameter(name='enable_assertions', choices=[True, False], type=bool, default=False,
-            help="Whether to enable assertions when compiling the test suite. This is only meaningful when "
-                 "running the tests against libc++.",
-            actions=lambda assertions: [
-              AddCompileFlag('-D_LIBCPP_ENABLE_ASSERTIONS=1'),
-              AddFeature('libcpp-has-assertions')
-            ] if assertions else []),
-
-  Parameter(name='additional_features', type=list, default=[],
-            help="A comma-delimited list of additional features that will be enabled when running the tests. "
-                 "This should be used sparingly since specifying ad-hoc features manually is error-prone and "
-                 "brittle in the long run as changes are made to the test suite.",
-            actions=lambda features: [AddFeature(f) for f in features]),
-
-  Parameter(name='enable_transitive_includes', choices=[True, False], type=bool, default=True,
-            help="Whether to enable backwards-compatibility transitive includes when running the tests. This "
-                 "is provided to ensure that the trimmed-down version of libc++ does not bit-rot in between "
-                 "points at which we bulk-remove transitive includes.",
-            actions=lambda enabled: [] if enabled else [
-              AddFeature('transitive-includes-disabled'),
-              AddCompileFlag('-D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES')
-            ]),
+            AddCompileFlag("-D_LIBCPP_ENABLE_EXPERIMENTAL"),
+        ]
+        if experimental
+        else [
+            AddFeature("libcpp-has-no-incomplete-format"),
+            AddFeature("libcpp-has-no-incomplete-pstl"),
+        ],
+    ),
+    Parameter(
+        name="long_tests",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable tests that take longer to run. This can be useful when running on a very slow device.",
+        actions=lambda enabled: [] if not enabled else [AddFeature("long_tests")],
+    ),
+    Parameter(
+        name="enable_assertions",
+        choices=[True, False],
+        type=bool,
+        default=False,
+        help="Whether to enable assertions when compiling the test suite. This is only meaningful when "
+        "running the tests against libc++.",
+        actions=lambda assertions: [
+            AddCompileFlag("-D_LIBCPP_ENABLE_ASSERTIONS=1"),
+            AddFeature("libcpp-has-assertions"),
+        ]
+        if assertions
+        else [],
+    ),
+    Parameter(
+        name="additional_features",
+        type=list,
+        default=[],
+        help="A comma-delimited list of additional features that will be enabled when running the tests. "
+        "This should be used sparingly since specifying ad-hoc features manually is error-prone and "
+        "brittle in the long run as changes are made to the test suite.",
+        actions=lambda features: [AddFeature(f) for f in features],
+    ),
+    Parameter(
+        name="enable_transitive_includes",
+        choices=[True, False],
+        type=bool,
+        default=True,
+        help="Whether to enable backwards-compatibility transitive includes when running the tests. This "
+        "is provided to ensure that the trimmed-down version of libc++ does not bit-rot in between "
+        "points at which we bulk-remove transitive includes.",
+        actions=lambda enabled: []
+        if enabled
+        else [
+            AddFeature("transitive-includes-disabled"),
+            AddCompileFlag("-D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES"),
+        ],
+    ),
 ]
diff --git a/libcxx/utils/run.py b/libcxx/utils/run.py
--- a/libcxx/utils/run.py
+++ b/libcxx/utils/run.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 """run.py is a utility for running a program.
 
@@ -21,10 +21,12 @@
 
 def main():
     parser = argparse.ArgumentParser()
-    parser.add_argument('--execdir', type=str, required=True)
-    parser.add_argument('--codesign_identity', type=str, required=False, default=None)
-    parser.add_argument('--env', type=str, nargs='*', required=False, default=[])
-    parser.add_argument('--prepend_env', type=str, nargs='*', required=False, default=[])
+    parser.add_argument("--execdir", type=str, required=True)
+    parser.add_argument("--codesign_identity", type=str, required=False, default=None)
+    parser.add_argument("--env", type=str, nargs="*", required=False, default=[])
+    parser.add_argument(
+        "--prepend_env", type=str, nargs="*", required=False, default=[]
+    )
     parser.add_argument("command", nargs=argparse.ONE_OR_MORE)
     args = parser.parse_args()
     commandLine = args.command
@@ -35,35 +37,37 @@
     # below. This allows us to do custom processing like codesigning test-executables.
     # It's also possible for there to be no such executable, for example in the case
     # of a .sh.cpp test.
-    isTestExe = lambda exe: exe.endswith('.tmp.exe') and os.path.exists(exe)
+    isTestExe = lambda exe: exe.endswith(".tmp.exe") and os.path.exists(exe)
 
     # Do any necessary codesigning of test-executables found in the command line.
     if args.codesign_identity:
         for exe in filter(isTestExe, commandLine):
-            subprocess.check_call(['xcrun', 'codesign', '-f', '-s', args.codesign_identity, exe], env={})
+            subprocess.check_call(
+                ["xcrun", "codesign", "-f", "-s", args.codesign_identity, exe], env={}
+            )
 
     # Extract environment variables into a dictionary
-    env = {k : v  for (k, v) in map(lambda s: s.split('=', 1), args.env)}
+    env = {k: v for (k, v) in map(lambda s: s.split("=", 1), args.env)}
 
     # Set environment variables where we prepend the given value to the
     # existing environment variable.
-    for (k, v) in map(lambda s: s.split('=', 1), args.prepend_env):
+    for (k, v) in map(lambda s: s.split("=", 1), args.prepend_env):
         if k in os.environ:
             v = v + os.pathsep + os.environ[k]
         env[k] = v
 
-    if platform.system() == 'Windows':
+    if platform.system() == "Windows":
         # Pass some extra variables through on Windows:
         # COMSPEC is needed for running subprocesses via std::system().
-        if 'COMSPEC' in os.environ:
-            env['COMSPEC'] = os.environ.get('COMSPEC')
+        if "COMSPEC" in os.environ:
+            env["COMSPEC"] = os.environ.get("COMSPEC")
         # TEMP is needed for placing temp files in a sensible directory.
-        if 'TEMP' in os.environ:
-            env['TEMP'] = os.environ.get('TEMP')
+        if "TEMP" in os.environ:
+            env["TEMP"] = os.environ.get("TEMP")
 
     # Run the command line with the given environment in the execution directory.
     return subprocess.call(commandLine, cwd=args.execdir, env=env, shell=False)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     exit(main())
diff --git a/libcxx/utils/ssh.py b/libcxx/utils/ssh.py
--- a/libcxx/utils/ssh.py
+++ b/libcxx/utils/ssh.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 
 """
 Runs an executable on a remote host.
@@ -25,37 +25,43 @@
 
 from shlex import quote as cmd_quote
 
+
 def ssh(args, command):
-    cmd = ['ssh', '-oBatchMode=yes']
+    cmd = ["ssh", "-oBatchMode=yes"]
     if args.extra_ssh_args is not None:
         cmd.extend(shlex.split(args.extra_ssh_args))
     return cmd + [args.host, command]
 
 
 def scp(args, src, dst):
-    cmd = ['scp', '-q', '-oBatchMode=yes']
+    cmd = ["scp", "-q", "-oBatchMode=yes"]
     if args.extra_scp_args is not None:
         cmd.extend(shlex.split(args.extra_scp_args))
-    return cmd + [src, '{}:{}'.format(args.host, dst)]
+    return cmd + [src, "{}:{}".format(args.host, dst)]
 
 
 def main():
     parser = argparse.ArgumentParser()
-    parser.add_argument('--host', type=str, required=True)
-    parser.add_argument('--execdir', type=str, required=True)
-    parser.add_argument('--tempdir', type=str, required=False, default='/tmp')
-    parser.add_argument('--extra-ssh-args', type=str, required=False)
-    parser.add_argument('--extra-scp-args', type=str, required=False)
-    parser.add_argument('--codesign_identity', type=str, required=False, default=None)
-    parser.add_argument('--env', type=str, nargs='*', required=False, default=[])
-    parser.add_argument('--prepend_env', type=str, nargs='*', required=False, default=[])
+    parser.add_argument("--host", type=str, required=True)
+    parser.add_argument("--execdir", type=str, required=True)
+    parser.add_argument("--tempdir", type=str, required=False, default="/tmp")
+    parser.add_argument("--extra-ssh-args", type=str, required=False)
+    parser.add_argument("--extra-scp-args", type=str, required=False)
+    parser.add_argument("--codesign_identity", type=str, required=False, default=None)
+    parser.add_argument("--env", type=str, nargs="*", required=False, default=[])
+    parser.add_argument(
+        "--prepend_env", type=str, nargs="*", required=False, default=[]
+    )
     parser.add_argument("command", nargs=argparse.ONE_OR_MORE)
     args = parser.parse_args()
     commandLine = args.command
 
     # Create a temporary directory where the test will be run.
     # That is effectively the value of %T on the remote host.
-    tmp = subprocess.check_output(ssh(args, 'mktemp -d {}/libcxx.XXXXXXXXXX'.format(args.tempdir)), universal_newlines=True).strip()
+    tmp = subprocess.check_output(
+        ssh(args, "mktemp -d {}/libcxx.XXXXXXXXXX".format(args.tempdir)),
+        universal_newlines=True,
+    ).strip()
 
     # HACK:
     # If an argument is a file that ends in `.tmp.exe`, assume it is the name
@@ -64,20 +70,23 @@
     # and changing their path when running on the remote host. It's also possible
     # for there to be no such executable, for example in the case of a .sh.cpp
     # test.
-    isTestExe = lambda exe: exe.endswith('.tmp.exe') and os.path.exists(exe)
+    isTestExe = lambda exe: exe.endswith(".tmp.exe") and os.path.exists(exe)
     pathOnRemote = lambda file: posixpath.join(tmp, os.path.basename(file))
 
     try:
         # Do any necessary codesigning of test-executables found in the command line.
         if args.codesign_identity:
             for exe in filter(isTestExe, commandLine):
-                subprocess.check_call(['xcrun', 'codesign', '-f', '-s', args.codesign_identity, exe], env={})
+                subprocess.check_call(
+                    ["xcrun", "codesign", "-f", "-s", args.codesign_identity, exe],
+                    env={},
+                )
 
         # tar up the execution directory (which contains everything that's needed
         # to run the test), and copy the tarball over to the remote host.
         try:
-            tmpTar = tempfile.NamedTemporaryFile(suffix='.tar', delete=False)
-            with tarfile.open(fileobj=tmpTar, mode='w') as tarball:
+            tmpTar = tempfile.NamedTemporaryFile(suffix=".tar", delete=False)
+            with tarfile.open(fileobj=tmpTar, mode="w") as tarball:
                 tarball.add(args.execdir, arcname=os.path.basename(args.execdir))
 
             # Make sure we close the file before we scp it, because accessing
@@ -93,22 +102,22 @@
 
         # Untar the dependencies in the temporary directory and remove the tarball.
         remoteCommands = [
-            'tar -xf {} -C {} --strip-components 1'.format(remoteTarball, tmp),
-            'rm {}'.format(remoteTarball)
+            "tar -xf {} -C {} --strip-components 1".format(remoteTarball, tmp),
+            "rm {}".format(remoteTarball),
         ]
 
         # Make sure all test-executables in the remote command line have 'execute'
         # permissions on the remote host. The host that compiled the test-executable
         # might not have a notion of 'executable' permissions.
         for exe in map(pathOnRemote, filter(isTestExe, commandLine)):
-            remoteCommands.append('chmod +x {}'.format(exe))
+            remoteCommands.append("chmod +x {}".format(exe))
 
         # Execute the command through SSH in the temporary directory, with the
         # correct environment. We tweak the command line to run it on the remote
         # host by transforming the path of test-executables to their path in the
         # temporary directory on the remote host.
         commandLine = (pathOnRemote(x) if isTestExe(x) else x for x in commandLine)
-        remoteCommands.append('cd {}'.format(tmp))
+        remoteCommands.append("cd {}".format(tmp))
 
         if args.prepend_env:
             # We can't sensibly know the original value of the env vars
@@ -117,17 +126,17 @@
 
         if args.env:
             env = list(map(cmd_quote, args.env))
-            remoteCommands.append('export {}'.format(' '.join(args.env)))
+            remoteCommands.append("export {}".format(" ".join(args.env)))
         remoteCommands.append(subprocess.list2cmdline(commandLine))
 
         # Finally, SSH to the remote host and execute all the commands.
-        rc = subprocess.call(ssh(args, ' && '.join(remoteCommands)))
+        rc = subprocess.call(ssh(args, " && ".join(remoteCommands)))
         return rc
 
     finally:
         # Make sure the temporary directory is removed when we're done.
-        subprocess.check_call(ssh(args, 'rm -r {}'.format(tmp)))
+        subprocess.check_call(ssh(args, "rm -r {}".format(tmp)))
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     exit(main())
diff --git a/libcxx/utils/sym_diff.py b/libcxx/utils/sym_diff.py
--- a/libcxx/utils/sym_diff.py
+++ b/libcxx/utils/sym_diff.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
-#===----------------------------------------------------------------------===##
+# ===----------------------------------------------------------------------===##
 """
 sym_diff - Compare two symbol lists and output the differences.
 """
@@ -17,34 +17,60 @@
 
 def main():
     parser = ArgumentParser(
-        description='Extract a list of symbols from a shared library.')
+        description="Extract a list of symbols from a shared library."
+    )
     parser.add_argument(
-        '--names-only', dest='names_only',
-        help='Only print symbol names',
-        action='store_true', default=False)
+        "--names-only",
+        dest="names_only",
+        help="Only print symbol names",
+        action="store_true",
+        default=False,
+    )
     parser.add_argument(
-        '--removed-only', dest='removed_only',
-        help='Only print removed symbols',
-        action='store_true', default=False)
-    parser.add_argument('--only-stdlib-symbols', dest='only_stdlib',
-                        help="Filter all symbols not related to the stdlib",
-                        action='store_true', default=False)
-    parser.add_argument('--strict', dest='strict',
-                        help="Exit with a non-zero status if any symbols "
-                             "differ",
-                        action='store_true', default=False)
+        "--removed-only",
+        dest="removed_only",
+        help="Only print removed symbols",
+        action="store_true",
+        default=False,
+    )
     parser.add_argument(
-        '-o', '--output', dest='output',
-        help='The output file. stdout is used if not given',
-        type=str, action='store', default=None)
+        "--only-stdlib-symbols",
+        dest="only_stdlib",
+        help="Filter all symbols not related to the stdlib",
+        action="store_true",
+        default=False,
+    )
     parser.add_argument(
-        '--demangle', dest='demangle', action='store_true', default=False)
+        "--strict",
+        dest="strict",
+        help="Exit with a non-zero status if any symbols " "differ",
+        action="store_true",
+        default=False,
+    )
     parser.add_argument(
-        'old_syms', metavar='old-syms', type=str,
-        help='The file containing the old symbol list or a library')
+        "-o",
+        "--output",
+        dest="output",
+        help="The output file. stdout is used if not given",
+        type=str,
+        action="store",
+        default=None,
+    )
     parser.add_argument(
-        'new_syms', metavar='new-syms', type=str,
-        help='The file containing the new symbol list or a library')
+        "--demangle", dest="demangle", action="store_true", default=False
+    )
+    parser.add_argument(
+        "old_syms",
+        metavar="old-syms",
+        type=str,
+        help="The file containing the old symbol list or a library",
+    )
+    parser.add_argument(
+        "new_syms",
+        metavar="new-syms",
+        type=str,
+        help="The file containing the new symbol list or a library",
+    )
     args = parser.parse_args()
 
     old_syms_list = util.extract_or_load(args.old_syms)
@@ -58,15 +84,16 @@
     if args.removed_only:
         added = {}
     report, is_break, is_different = diff.report_diff(
-        added, removed, changed, names_only=args.names_only,
-        demangle=args.demangle)
+        added, removed, changed, names_only=args.names_only, demangle=args.demangle
+    )
     if args.output is None:
         print(report)
     else:
-        with open(args.output, 'w') as f:
-            f.write(report + '\n')
+        with open(args.output, "w") as f:
+            f.write(report + "\n")
     exit_code = 1 if is_break or (args.strict and is_different) else 0
     sys.exit(exit_code)
 
-if __name__ == '__main__':
+
+if __name__ == "__main__":
     main()
diff --git a/libcxxabi/test/lit.cfg.py b/libcxxabi/test/lit.cfg.py
--- a/libcxxabi/test/lit.cfg.py
+++ b/libcxxabi/test/lit.cfg.py
@@ -7,4 +7,5 @@
 lit_config.fatal(
     "You seem to be running Lit directly -- you should be running Lit through "
     "<build>/bin/llvm-lit, which will ensure that the right Lit configuration "
-    "file is used.")
+    "file is used."
+)
diff --git a/libcxxabi/test/native/arm-linux-eabi/lit.local.cfg b/libcxxabi/test/native/arm-linux-eabi/lit.local.cfg
--- a/libcxxabi/test/native/arm-linux-eabi/lit.local.cfg
+++ b/libcxxabi/test/native/arm-linux-eabi/lit.local.cfg
@@ -1,6 +1,9 @@
 def is_arm_linux_eabi(triple):
-    return ('arm' in triple) and ('linux' in triple) and ('eabi' in triple)
+    return ("arm" in triple) and ("linux" in triple) and ("eabi" in triple)
 
-is_native = hasattr(config.root, 'target_triple') and (config.root.host_triple == config.root.target_triple)
+
+is_native = hasattr(config.root, "target_triple") and (
+    config.root.host_triple == config.root.target_triple
+)
 if not is_native or not is_arm_linux_eabi(config.root.host_triple):
     config.unsupported = True
diff --git a/libunwind/docs/conf.py b/libunwind/docs/conf.py
--- a/libunwind/docs/conf.py
+++ b/libunwind/docs/conf.py
@@ -16,106 +16,106 @@
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
+# sys.path.insert(0, os.path.abspath('.'))
 
 # -- General configuration -----------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
+# needs_sphinx = '1.0'
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.intersphinx', 'sphinx.ext.todo']
+extensions = ["sphinx.ext.intersphinx", "sphinx.ext.todo"]
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
+templates_path = ["_templates"]
 
 # The suffix of source filenames.
-source_suffix = '.rst'
+source_suffix = ".rst"
 
 # The encoding of source files.
-#source_encoding = 'utf-8-sig'
+# source_encoding = 'utf-8-sig'
 
 # The master toctree document.
-master_doc = 'index'
+master_doc = "index"
 
 # General information about the project.
-project = u'libunwind'
-copyright = u'2011-%d, LLVM Project' % date.today().year
+project = "libunwind"
+copyright = "2011-%d, LLVM Project" % date.today().year
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = '17.0'
+version = "17.0"
 # The full version, including alpha/beta/rc tags.
-release = '17.0'
+release = "17.0"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
-#language = None
+# language = None
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
-#today = ''
+# today = ''
 # Else, today_fmt is used as the format for a strftime call.
-today_fmt = '%Y-%m-%d'
+today_fmt = "%Y-%m-%d"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
-exclude_patterns = ['_build']
+exclude_patterns = ["_build"]
 
 # The reST default role (used for this markup: `text`) to use for all documents.
-#default_role = None
+# default_role = None
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
+# add_function_parentheses = True
 
 # If true, the current module name will be prepended to all description
 # unit titles (such as .. function::).
-#add_module_names = True
+# add_module_names = True
 
 # If true, sectionauthor and moduleauthor directives will be shown in the
 # output. They are ignored by default.
 show_authors = True
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'friendly'
+pygments_style = "friendly"
 
 # A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
+# modindex_common_prefix = []
 
 
 # -- Options for HTML output ---------------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'haiku'
+html_theme = "haiku"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-#html_theme_options = {}
+# html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
-#html_theme_path = []
+# html_theme_path = []
 
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
-#html_title = None
+# html_title = None
 
 # A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
+# html_short_title = None
 
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-#html_logo = None
+# html_logo = None
 
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
-#html_favicon = None
+# html_favicon = None
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
@@ -124,101 +124,95 @@
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
+# html_last_updated_fmt = '%b %d, %Y'
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
-#html_use_smartypants = True
+# html_use_smartypants = True
 
 # Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
+# html_sidebars = {}
 
 # Additional templates that should be rendered to pages, maps page names to
 # template names.
-#html_additional_pages = {}
+# html_additional_pages = {}
 
 # If false, no module index is generated.
-#html_domain_indices = True
+# html_domain_indices = True
 
 # If false, no index is generated.
-#html_use_index = True
+# html_use_index = True
 
 # If true, the index is split into individual pages for each letter.
-#html_split_index = False
+# html_split_index = False
 
 # If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
+# html_show_sourcelink = True
 
 # If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
+# html_show_sphinx = True
 
 # If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
+# html_show_copyright = True
 
 # If true, an OpenSearch description file will be output, and all pages will
 # contain a <link> tag referring to it.  The value of this option must be the
 # base URL from which the finished HTML is served.
-#html_use_opensearch = ''
+# html_use_opensearch = ''
 
 # This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
+# html_file_suffix = None
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = 'libunwinddoc'
+htmlhelp_basename = "libunwinddoc"
 
 
 # -- Options for LaTeX output --------------------------------------------------
 
 latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
+    # The paper size ('letterpaper' or 'a4paper').
+    #'papersize': 'letterpaper',
+    # The font size ('10pt', '11pt' or '12pt').
+    #'pointsize': '10pt',
+    # Additional stuff for the LaTeX preamble.
+    #'preamble': '',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto/manual]).
 latex_documents = [
-  ('contents', 'libunwind.tex', u'libunwind Documentation',
-   u'LLVM project', 'manual'),
+    ("contents", "libunwind.tex", "libunwind Documentation", "LLVM project", "manual"),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
-#latex_logo = None
+# latex_logo = None
 
 # For "manual" documents, if this is true, then toplevel headings are parts,
 # not chapters.
-#latex_use_parts = False
+# latex_use_parts = False
 
 # If true, show page references after internal links.
-#latex_show_pagerefs = False
+# latex_show_pagerefs = False
 
 # If true, show URL addresses after external links.
-#latex_show_urls = False
+# latex_show_urls = False
 
 # Documents to append as an appendix to all manuals.
-#latex_appendices = []
+# latex_appendices = []
 
 # If false, no module index is generated.
-#latex_domain_indices = True
+# latex_domain_indices = True
 
 
 # -- Options for manual page output --------------------------------------------
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [
-    ('contents', 'libunwind', u'libunwind Documentation',
-     [u'LLVM project'], 1)
-]
+man_pages = [("contents", "libunwind", "libunwind Documentation", ["LLVM project"], 1)]
 
 # If true, show URL addresses after external links.
-#man_show_urls = False
+# man_show_urls = False
 
 
 # -- Options for Texinfo output ------------------------------------------------
@@ -227,19 +221,25 @@
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
-  ('contents', 'libunwind', u'libunwind Documentation',
-   u'LLVM project', 'libunwind', 'LLVM Unwinder',
-   'Miscellaneous'),
+    (
+        "contents",
+        "libunwind",
+        "libunwind Documentation",
+        "LLVM project",
+        "libunwind",
+        "LLVM Unwinder",
+        "Miscellaneous",
+    ),
 ]
 
 # Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
+# texinfo_appendices = []
 
 # If false, no module index is generated.
-#texinfo_domain_indices = True
+# texinfo_domain_indices = True
 
 # How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
+# texinfo_show_urls = 'footnote'
 
 
 # FIXME: Define intersphinx configuration.
diff --git a/libunwind/test/lit.cfg.py b/libunwind/test/lit.cfg.py
--- a/libunwind/test/lit.cfg.py
+++ b/libunwind/test/lit.cfg.py
@@ -7,4 +7,5 @@
 lit_config.fatal(
     "You seem to be running Lit directly -- you should be running Lit through "
     "<build>/bin/llvm-lit, which will ensure that the right Lit configuration "
-    "file is used.")
+    "file is used."
+)