[libc++][format] Adds bool formatter.

[Mordante]

Summary

Implements the formatter for Boolean types.
[format.formatter.spec]/2.3
For each charT, for each cv-unqualified arithmetic type ArithmeticT other
than char, wchar_t, char8_t, char16_t, or char32_t, a specialization

template<> struct formatter<ArithmeticT, charT>;

This removes the stub implemented in D96664.

Implements parts of:

• P0645 Text Formatting
• P1652 Printf corner cases in std::format

Completes:

• P1868 width: clarifying units of width and precision in std::format

[Mordante]

This patch will be updated due to changes in other patches in the series.

[Mordante]

Rebased and updated:

• Address some changes from previous patches
• Minor cleanups and comment improvements
• Added a module map

[Mordante]

libcxx/test/std/utilities/format/format.functions/tests.inc

493

Remove this replacement with the method @Quuxplusone suggested in D96664.

[Mordante]

Rebase.
Use the method for '\0' in the tests as suggested in D96664.

[vitaut]

libcxx/test/std/utilities/format/format.functions/tests.inc

455–456

As in D103466: . alone is not a prevision field.

[Mordante]

libcxx/test/std/utilities/format/format.functions/tests.inc

455–456

Like there the message has changed.

[Mordante]

Rebase
Use private module headers
Guard unit tests for implementation details

[Mordante]

libcxx/include/__format/formatter_bool.h

52

https://reviews.llvm.org/D103413#inline-991405

[Mordante]

Needs updates due to changes in D103368.

[Mordante]

Rebased and adjusted for chandges in main
Retarget for LLVM 14.
s/_LIBCPP_INLINE_VISIBILITY/_LIBCPP_HIDE_FROM_ABI/
Generate private module tests

[vitaut]

Two minor comments inline, otherwise LGTM.

libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp

257

This line is the same as above. Did you mean to test false here?

273–275

Maybe also test that the default alignment is left?

[Mordante]

Thanks for the review!

libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp

257

Indeed, seems a copy-paste error.

[Mordante]

Addresses review comments.

[Mordante]

Rebased and adjusted for changes in main
s/_LIBCPP_INLINE_VISIBILITY/_LIBCPP_HIDE_FROM_ABI/

[Mordante]

Remove the unneeded _LIBCPP_PUSH_MACROS.
Updated code to changes earlier in the patch series.

libcxx/docs/Status/Cxx20Papers.csv

 "","","","","",""
 "`P0586 <https://wg21.link/P0586>`__","LWG","Safe integral comparisons","Prague","|Complete|","13.0"
 "`P0593 <https://wg21.link/P0593>`__","CWG","Implicit creation of objects for low-level object manipulation","Prague","* *",""
 "`P1115 <https://wg21.link/P1115>`__","LWG","Improving the Return Value of Erase-Like Algorithms II: Free erase/erase if","Prague","|Complete|","11.0"
 "`P1243 <https://wg21.link/P1243>`__","LWG","Rangify New Algorithms","Prague","* *",""
 "`P1460 <https://wg21.link/P1460>`__","LWG","Mandating the Standard Library: Clause 20 - Utilities library","Prague","* *",""
 "`P1739 <https://wg21.link/P1739>`__","LWG","Avoid template bloat for safe_ranges in combination with ""subrange-y"" view adaptors","Prague","* *",""
 "`P1831 <https://wg21.link/P1831>`__","LWG","Deprecating volatile: library","Prague","* *",""
-"`P1868 <https://wg21.link/P1868>`__","LWG","width: clarifying units of width and precision in std::format","Prague","|In Progress|",""
+"`P1868 <https://wg21.link/P1868>`__","LWG","width: clarifying units of width and precision in std::format","Prague","|Complete|","14.0"
 "`P1908 <https://wg21.link/P1908>`__","CWG","Reserving Attribute Namespaces for Future Use","Prague","* *",""
 "`P1937 <https://wg21.link/P1937>`__","CWG","Fixing inconsistencies between constexpr and consteval functions","Prague","* *",""
 "`P1956 <https://wg21.link/P1956>`__","LWG","On the names of low-level bit manipulation functions","Prague","|Complete|","12.0"
 "`P1957 <https://wg21.link/P1957>`__","CWG","Converting from ``T*``\  to bool should be considered narrowing (re: US 212)","Prague","* *",""
 "`P1963 <https://wg21.link/P1963>`__","LWG","Fixing US 313","Prague","* *",""
 "`P1964 <https://wg21.link/P1964>`__","LWG","Wording for boolean-testable","Prague","|Complete|","13.0"
 "`P1970 <https://wg21.link/P1970>`__","LWG","Consistency for size() functions: Add ranges::ssize","Prague","* *",""
 "`P1973 <https://wg21.link/P1973>`__","LWG","Rename ""_default_init"" Functions, Rev1","Prague","* *",""

libcxx/include/CMakeLists.txt

set(files
   __format/format_arg.h
   __format/format_args.h
   __format/format_context.h
   __format/format_error.h
   __format/format_fwd.h
   __format/format_parse_context.h
   __format/format_string.h
   __format/formatter.h
+  __format/formatter_bool.h
   __format/formatter_char.h
   __format/formatter_integer.h
   __format/formatter_integral.h
   __format/formatter_string.h
   __format/parser_std_format_spec.h
   __function_like.h
   __functional_base
   __functional/binary_function.h

libcxx/include/__format/formatter_bool.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FORMAT_FORMATTER_BOOL_H
+#define _LIBCPP___FORMAT_FORMATTER_BOOL_H
+
+#include <__availability>
+#include <__config>
+#include <__format/format_error.h>
+#include <__format/format_fwd.h>
+#include <__format/formatter.h>
+#include <__format/formatter_integral.h>
+#include <__format/parser_std_format_spec.h>
+#include <string_view>
+
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#include <locale>
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+// TODO FMT Remove this once we require compilers with proper C++20 support.
+// If the compiler has no concepts support, the format header will be disabled.
+// Without concepts support enable_if needs to be used and that too much effort
+// to support compilers with partial C++20 support.
+#if !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+namespace __format_spec {
+
+template <class _CharT>
+class _LIBCPP_TEMPLATE_VIS __parser_bool : public __parser_integral<_CharT> {
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(auto& __parse_ctx)
+      -> decltype(__parse_ctx.begin()) {
+    auto __it = __parser_integral<_CharT>::__parse(__parse_ctx);
+
+    switch (this->__type) {
+    case _Flags::_Type::__default:
+      this->__type = _Flags::_Type::__string;
+      [[fallthrough]];
+    case _Flags::_Type::__string:
+      this->__handle_bool();
+      break;
+
+    case _Flags::_Type::__char:
+      this->__handle_char();
+      break;
+
+    case _Flags::_Type::__binary_lower_case:
+    case _Flags::_Type::__binary_upper_case:
+    case _Flags::_Type::__octal:
+    case _Flags::_Type::__decimal:
+    case _Flags::_Type::__hexadecimal_lower_case:
+    case _Flags::_Type::__hexadecimal_upper_case:
+      this->__handle_integer();
+      break;
+
+    default:
+      __throw_format_error(
+          "The format-spec type has a type not supported for a bool argument");
+    }
+
+    return __it;
+  }
+};
+
+template <class _CharT>
+struct _LIBCPP_TEMPLATE_VIS __bool_strings;
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS __bool_strings<char> {
+  static constexpr string_view __true{"true"};
+  static constexpr string_view __false{"false"};
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS __bool_strings<wchar_t> {
+  static constexpr wstring_view __true{L"true"};
+  static constexpr wstring_view __false{L"false"};
+};
+
+template <class _CharT>
+using __formatter_bool = __formatter_integral<__parser_bool<_CharT>>;
+
+} //namespace __format_spec
+
+// [format.formatter.spec]/2.3
+// For each charT, for each cv-unqualified arithmetic type ArithmeticT other
+// than char, wchar_t, char8_t, char16_t, or char32_t, a specialization
+
+template <class _CharT>
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<bool, _CharT>
+    : public __format_spec::__formatter_bool<_CharT> {
+  using _Base = __format_spec::__formatter_bool<_CharT>;
+
+  _LIBCPP_HIDE_FROM_ABI auto format(bool __value, auto& __ctx)
+      -> decltype(__ctx.out()) {
+    if (this->__type != __format_spec::_Flags::_Type::__string)
+      return _Base::format(static_cast<unsigned char>(__value), __ctx);
+
+    if (this->__width_needs_substitution())
+      this->__substitute_width_arg_id(__ctx.arg(this->__width));
+
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+    if (this->__locale_specific_form) {
+      const auto& __np = use_facet<numpunct<_CharT>>(__ctx.locale());
+      basic_string<_CharT> __str = __value ? __np.truename() : __np.falsename();
+      return __formatter::__write_unicode(
+          __ctx.out(), basic_string_view<_CharT>{__str}, this->__width, -1,
+          this->__fill, this->__alignment);
+    }
+#endif
+    basic_string_view<_CharT> __str =
+        __value ? __format_spec::__bool_strings<_CharT>::__true
+                : __format_spec::__bool_strings<_CharT>::__false;
+
+    // The output only uses ASCII so every character is one column.
+    unsigned __size = __str.size();
+    if (__size >= this->__width)
+      return _VSTD::copy(__str.begin(), __str.end(), __ctx.out());
+
+    return __formatter::__write(__ctx.out(), __str.begin(), __str.end(), __size,
+                                this->__width, this->__fill, this->__alignment);
+  }
+};
+
+#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+#endif //_LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___FORMAT_FORMATTER_BOOL_H

libcxx/include/format

 #include <__format/format_arg.h>
 #include <__format/format_args.h>
 #include <__format/format_context.h>
 #include <__format/format_error.h>
 #include <__format/format_fwd.h>
 #include <__format/format_parse_context.h>
 #include <__format/format_string.h>
 #include <__format/formatter.h>
+#include <__format/formatter_bool.h>
 #include <__format/formatter_char.h>
 #include <__format/formatter_integer.h>
 #include <__format/formatter_string.h>
 #include <__format/parser_std_format_spec.h>
 #include <__variant/monostate.h>
 #include <array>
 #include <concepts>
 #include <string>
_LIBCPP_HIDDEN auto __handle_format(_Uv __value, auto& __ctx)
     return __out_it;
   }
 };
 } // namespace __format
 
 // These specializations are helper stubs and not proper formatters.
 // TODO FMT Implement the proper formatter specializations.
 
-// [format.formatter.spec]/2.3
-// For each charT, for each cv-unqualified arithmetic type ArithmeticT other
-// than char, wchar_t, char8_t, char16_t, or char32_t, a specialization
-
-// Boolean.
-template <class _CharT>
-struct _LIBCPP_TEMPLATE_VIS formatter<bool, _CharT> {
-  _LIBCPP_HIDE_FROM_ABI
-  auto parse(auto& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    // TODO FMT Implement
-    return __parse_ctx.begin();
-  }
-
-  _LIBCPP_HIDE_FROM_ABI
-  auto format(bool __b, auto& __ctx) -> decltype(__ctx.out()) {
-    // TODO FMT Implement using formatting arguments
-    auto __out_it = __ctx.out();
-    *__out_it++ = _CharT('0') + __b;
-    return __out_it;
-  }
-};
-
 // Floating point types.
 // TODO FMT There are no replacements for the floating point stubs due to not
 // having floating point support in std::to_chars yet. These stubs aren't
 // removed since they are useful for developing the real versions.
 // Ultimately the stubs should be implemented properly and this code can be
 // removed.
 #if 0
 template <class _CharT>

libcxx/include/module.modulemap

module __format {
         export optional
         export locale
       }
       module format_error           { private header "__format/format_error.h"           }
       module format_fwd             { private header "__format/format_fwd.h"             }
       module format_parse_context   { private header "__format/format_parse_context.h"   }
       module format_string          { private header "__format/format_string.h"          }
       module formatter              { private header "__format/formatter.h"              }
+      module formatter_bool         { private header "__format/formatter_bool.h"         }
       module formatter_char         { private header "__format/formatter_char.h"         }
       module formatter_integer      { private header "__format/formatter_integer.h"      }
       module formatter_integral     { private header "__format/formatter_integral.h"     }
       module formatter_string       { private header "__format/formatter_string.h"       }
       module parser_std_format_spec { private header "__format/parser_std_format_spec.h" }
     }
   }
   module forward_list {

libcxx/test/libcxx/diagnostics/detail.headers/format/formatter_bool.module.verify.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__format/formatter_bool.h'}}
+#include <__format/formatter_bool.h>

libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_bool.pass.cpp

+//===----------------------------------------------------------------------===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+// UNSUPPORTED: libcpp-has-no-incomplete-format
+
+// <format>
+
+// Tests the parsing of the format string as specified in [format.string.std].
+// It validates whether the std-format-spec is valid for a boolean type.
+
+#include <format>
+#include <cassert>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#include <iostream>
+#endif
+
+#include "concepts_precision.h"
+#include "test_macros.h"
+#include "make_string.h"
+
+#define CSTR(S) MAKE_CSTRING(CharT, S)
+
+using namespace std::__format_spec;
+
+template <class CharT>
+using parser = __parser_bool<CharT>;
+
+#include "test_exception.h" // requires parser
+
+template <class CharT>
+struct Expected {
+  CharT fill = CharT(' ');
+  _Flags::_Alignment alignment = _Flags::_Alignment::__left;
+  _Flags::_Sign sign = _Flags::_Sign::__default;
+  bool alternate_form = false;
+  bool zero_padding = false;
+  uint32_t width = 0;
+  bool width_as_arg = false;
+  bool locale_specific_form = false;
+  _Flags::_Type type = _Flags::_Type::__string;
+};
+
+template <class CharT>
+constexpr void test(Expected<CharT> expected, size_t size,
+                    std::basic_string_view<CharT> fmt) {
+  // Initialize parser with sufficient arguments to avoid the parsing to fail
+  // due to insufficient arguments.
+  std::basic_format_parse_context<CharT> parse_ctx(fmt,
+                                                   std::__format::__number_max);
+  auto begin = parse_ctx.begin();
+  auto end = parse_ctx.end();
+  parser<CharT> parser;
+  auto it = parser.parse(parse_ctx);
+
+  assert(begin == parse_ctx.begin());
+  assert(end == parse_ctx.end());
+
+  assert(begin + size == it);
+  assert(parser.__fill == expected.fill);
+  assert(parser.__alignment == expected.alignment);
+  assert(parser.__sign == expected.sign);
+  assert(parser.__alternate_form == expected.alternate_form);
+  assert(parser.__zero_padding == expected.zero_padding);
+  assert(parser.__width == expected.width);
+  assert(parser.__width_as_arg == expected.width_as_arg);
+  assert(parser.__locale_specific_form == expected.locale_specific_form);
+  assert(parser.__type == expected.type);
+}
+
+template <class CharT>
+constexpr void test(Expected<CharT> expected, size_t size, const CharT* f) {
+  // The format-spec is valid if completely consumed or terminates at a '}'.
+  // The valid inputs all end with a '}'. The test is executed twice:
+  // - first with the terminating '}',
+  // - second consuming the entire input.
+  std::basic_string_view<CharT> fmt{f};
+  assert(fmt.back() == CharT('}') && "Pre-condition failure");
+
+  test(expected, size, fmt);
+  fmt.remove_suffix(1);
+  test(expected, size, fmt);
+}
+
+template <class CharT>
+constexpr void test_as_string() {
+
+  test({}, 1, CSTR("s}"));
+
+  // *** Align-fill ***
+  test({.alignment = _Flags::_Alignment::__left}, 1, CSTR("<}"));
+  test({.alignment = _Flags::_Alignment::__center}, 1, "^}");
+  test({.alignment = _Flags::_Alignment::__right}, 1, ">}");
+
+  test({.alignment = _Flags::_Alignment::__left}, 2, CSTR("<s}"));
+  test({.alignment = _Flags::_Alignment::__center}, 2, "^s}");
+  test({.alignment = _Flags::_Alignment::__right}, 2, ">s}");
+
+  test({.fill = CharT('L'), .alignment = _Flags::_Alignment::__left}, 2,
+       CSTR("L<}"));
+  test({.fill = CharT('#'), .alignment = _Flags::_Alignment::__center}, 2,
+       CSTR("#^}"));
+  test({.fill = CharT('0'), .alignment = _Flags::_Alignment::__right}, 2,
+       CSTR("0>}"));
+
+  test({.fill = CharT('L'), .alignment = _Flags::_Alignment::__left}, 3,
+       CSTR("L<s}"));
+  test({.fill = CharT('#'), .alignment = _Flags::_Alignment::__center}, 3,
+       CSTR("#^s}"));
+  test({.fill = CharT('0'), .alignment = _Flags::_Alignment::__right}, 3,
+       CSTR("0>s}"));
+
+  // *** Sign ***
+  test_exception("A sign field isn't allowed in this format-spec", CSTR("-}"));
+  test_exception("A sign field isn't allowed in this format-spec", CSTR("-s}"));
+
+  // *** Alternate form ***
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 CSTR("#}"));
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 CSTR("#s}"));
+
+  // *** Zero padding ***
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 CSTR("0}"));
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 CSTR("0s}"));
+
+  // *** Width ***
+  test({.width = 0, .width_as_arg = false}, 0, CSTR("}"));
+  test({.width = 1, .width_as_arg = false}, 1, CSTR("1}"));
+  test({.width = 10, .width_as_arg = false}, 2, CSTR("10}"));
+  test({.width = 1000, .width_as_arg = false}, 4, CSTR("1000}"));
+  test({.width = 1000000, .width_as_arg = false}, 7, CSTR("1000000}"));
+
+  test({.width = 0, .width_as_arg = true}, 2, CSTR("{}}"));
+  test({.width = 0, .width_as_arg = true}, 3, CSTR("{0}}"));
+  test({.width = 1, .width_as_arg = true}, 3, CSTR("{1}}"));
+
+  test_exception("A format-spec width field shouldn't have a leading zero",
+                 CSTR("00"));
+
+  static_assert(std::__format::__number_max == 2'147'483'647,
+                "Update the assert and the test.");
+  test({.width = 2'147'483'647, .width_as_arg = false}, 10,
+       CSTR("2147483647}"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("2147483648"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("5000000000"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("10000000000"));
+
+  test_exception("End of input while parsing format-spec arg-id", CSTR("{"));
+  test_exception("A format-spec arg-id should terminate at a '}'", CSTR("{0"));
+  test_exception(
+      "The arg-id of the format-spec starts with an invalid character",
+      CSTR("{a"));
+  test_exception("A format-spec arg-id should terminate at a '}'", CSTR("{1"));
+  test_exception("A format-spec arg-id should terminate at a '}'", CSTR("{9"));
+  test_exception("A format-spec arg-id should terminate at a '}'", CSTR("{9:"));
+  test_exception("A format-spec arg-id should terminate at a '}'", CSTR("{9a"));
+
+  static_assert(std::__format::__number_max == 2'147'483'647,
+                "Update the assert and the test.");
+  // Note the static_assert tests whether the arg-id is valid.
+  // Therefore the following should be true arg-id < __format::__number_max.
+  test({.width = 2'147'483'646, .width_as_arg = true}, 12,
+       CSTR("{2147483646}}"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("{2147483648}"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("{5000000000}"));
+  test_exception("The numeric value of the format-spec is too large",
+                 CSTR("{10000000000}"));
+
+  // *** Precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR("."));
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR(".1"));
+
+  // *** Locale-specific form ***
+  test({.locale_specific_form = true}, 1, CSTR("L}"));
+  test({.locale_specific_form = true}, 2, CSTR("Ls}"));
+}
+
+template <class CharT>
+constexpr void test_as_char() {
+
+  test({.type = _Flags::_Type::__char}, 1, CSTR("c}"));
+
+  // *** Align-fill ***
+  test({.alignment = _Flags::_Alignment::__left, .type = _Flags::_Type::__char},
+       2, CSTR("<c}"));
+  test({.alignment = _Flags::_Alignment::__center,
+        .type = _Flags::_Type::__char},
+       2, "^c}");
+  test(
+      {.alignment = _Flags::_Alignment::__right, .type = _Flags::_Type::__char},
+      2, ">c}");
+
+  test({.fill = CharT('L'),
+        .alignment = _Flags::_Alignment::__left,
+        .type = _Flags::_Type::__char},
+       3, CSTR("L<c}"));
+  test({.fill = CharT('#'),
+        .alignment = _Flags::_Alignment::__center,
+        .type = _Flags::_Type::__char},
+       3, CSTR("#^c}"));
+  test({.fill = CharT('0'),
+        .alignment = _Flags::_Alignment::__right,
+        .type = _Flags::_Type::__char},
+       3, CSTR("0>c}"));
+
+  // *** Sign ***
+  test_exception("A sign field isn't allowed in this format-spec", CSTR("-c}"));
+
+  // *** Alternate form ***
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 CSTR("#c}"));
+
+  // *** Zero padding ***
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 CSTR("0c}"));
+
+  // *** Width ***
+  test({.width = 0, .width_as_arg = false, .type = _Flags::_Type::__char}, 1,
+       CSTR("c}"));
+  test({.width = 1, .width_as_arg = false, .type = _Flags::_Type::__char}, 2,
+       CSTR("1c}"));
+  test({.width = 10, .width_as_arg = false, .type = _Flags::_Type::__char}, 3,
+       CSTR("10c}"));
+  test({.width = 1000, .width_as_arg = false, .type = _Flags::_Type::__char}, 5,
+       CSTR("1000c}"));
+  test({.width = 1000000, .width_as_arg = false, .type = _Flags::_Type::__char},
+       8, CSTR("1000000c}"));
+
+  test({.width = 0, .width_as_arg = true, .type = _Flags::_Type::__char}, 3,
+       CSTR("{}c}"));
+  test({.width = 0, .width_as_arg = true, .type = _Flags::_Type::__char}, 4,
+       CSTR("{0}c}"));
+  test({.width = 1, .width_as_arg = true, .type = _Flags::_Type::__char}, 4,
+       CSTR("{1}c}"));
+
+  // *** Precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR("."));
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR(".1"));
+
+  // *** Locale-specific form ***
+  test({.locale_specific_form = true, .type = _Flags::_Type::__char}, 2,
+       CSTR("Lc}"));
+}
+
+template <class CharT>
+constexpr void test_as_integer() {
+
+  test({.alignment = _Flags::_Alignment::__right,
+        .type = _Flags::_Type::__decimal},
+       1, CSTR("d}"));
+
+  // *** Align-fill ***
+  test({.alignment = _Flags::_Alignment::__left,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("<d}"));
+  test({.alignment = _Flags::_Alignment::__center,
+        .type = _Flags::_Type::__decimal},
+       2, "^d}");
+  test({.alignment = _Flags::_Alignment::__right,
+        .type = _Flags::_Type::__decimal},
+       2, ">d}");
+
+  test({.fill = CharT('L'),
+        .alignment = _Flags::_Alignment::__left,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("L<d}"));
+  test({.fill = CharT('#'),
+        .alignment = _Flags::_Alignment::__center,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("#^d}"));
+  test({.fill = CharT('0'),
+        .alignment = _Flags::_Alignment::__right,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("0>d}"));
+
+  // *** Sign ***
+  test({.alignment = _Flags::_Alignment::__right,
+        .sign = _Flags::_Sign::__minus,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("-d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .sign = _Flags::_Sign::__plus,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("+d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .sign = _Flags::_Sign::__space,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR(" d}"));
+
+  // *** Alternate form ***
+  test({.alignment = _Flags::_Alignment::__right,
+        .alternate_form = true,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("#d}"));
+
+  // *** Zero padding ***
+  test({.alignment = _Flags::_Alignment::__default,
+        .zero_padding = true,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("0d}"));
+  test({.alignment = _Flags::_Alignment::__center,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("^0d}"));
+
+  // *** Width ***
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 0,
+        .width_as_arg = false,
+        .type = _Flags::_Type::__decimal},
+       1, CSTR("d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 1,
+        .width_as_arg = false,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("1d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 10,
+        .width_as_arg = false,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("10d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 1000,
+        .width_as_arg = false,
+        .type = _Flags::_Type::__decimal},
+       5, CSTR("1000d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 1000000,
+        .width_as_arg = false,
+        .type = _Flags::_Type::__decimal},
+       8, CSTR("1000000d}"));
+
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 0,
+        .width_as_arg = true,
+        .type = _Flags::_Type::__decimal},
+       3, CSTR("{}d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 0,
+        .width_as_arg = true,
+        .type = _Flags::_Type::__decimal},
+       4, CSTR("{0}d}"));
+  test({.alignment = _Flags::_Alignment::__right,
+        .width = 1,
+        .width_as_arg = true,
+        .type = _Flags::_Type::__decimal},
+       4, CSTR("{1}d}"));
+
+  // *** Precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR("."));
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR(".1"));
+
+  // *** Locale-specific form ***
+  test({.alignment = _Flags::_Alignment::__right,
+        .locale_specific_form = true,
+        .type = _Flags::_Type::__decimal},
+       2, CSTR("Ld}"));
+}
+
+template <class CharT>
+constexpr void test() {
+  parser<CharT> parser;
+
+  assert(parser.__fill == CharT(' '));
+  assert(parser.__alignment == _Flags::_Alignment::__default);
+  assert(parser.__sign == _Flags::_Sign::__default);
+  assert(parser.__alternate_form == false);
+  assert(parser.__zero_padding == false);
+  assert(parser.__width == 0);
+  assert(parser.__width_as_arg == false);
+  static_assert(!has_precision<decltype(parser)>);
+  static_assert(!has_precision_as_arg<decltype(parser)>);
+  assert(parser.__locale_specific_form == false);
+  assert(parser.__type == _Flags::_Type::__default);
+
+  test({}, 0, CSTR("}"));
+
+  test_as_string<CharT>();
+  test_as_char<CharT>();
+  test_as_integer<CharT>();
+
+  // *** Type ***
+  {
+    const char* expected =
+        "The format-spec type has a type not supported for a bool argument";
+    test_exception(expected, CSTR("A}"));
+    test_exception(expected, CSTR("E}"));
+    test_exception(expected, CSTR("F}"));
+    test_exception(expected, CSTR("G}"));
+    test_exception(expected, CSTR("a}"));
+    test_exception(expected, CSTR("e}"));
+    test_exception(expected, CSTR("f}"));
+    test_exception(expected, CSTR("g}"));
+    test_exception(expected, CSTR("p}"));
+  }
+
+  // **** General ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 CSTR("ss"));
+}
+
+constexpr bool test() {
+  test<char>();
+  test<wchar_t>();
+
+  return true;
+}
+
+int main(int, char**) {
+#ifndef _WIN32
+  // Make sure the parsers match the expectations. The layout of the
+  // subobjects is chosen to minimize the size required.
+  static_assert(sizeof(parser<char>) == 2 * sizeof(uint32_t));
+  static_assert(
+      sizeof(parser<wchar_t>) ==
+      (sizeof(wchar_t) <= 2 ? 2 * sizeof(uint32_t) : 3 * sizeof(uint32_t)));
+#endif
+
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.bool.pass.cpp

void test_termination_condition(StringT expected, StringT f, bool arg) {
 
   test(expected, fmt, arg);
   fmt.remove_suffix(1);
   test(expected, fmt, arg);
 }
 
 template <class CharT>
 void test_boolean() {
-  test_termination_condition(STR("1"), STR("}"), true);
-  test_termination_condition(STR("0"), STR("}"), false);
+  test_termination_condition(STR("true"), STR("}"), true);
+  test_termination_condition(STR("false"), STR("}"), false);
 }
 
 int main(int, char**) {
   test_boolean<char>();
   test_boolean<wchar_t>();
 
   return 0;
 }

libcxx/test/std/utilities/format/format.functions/format_to.locale.pass.cpp

void test(std::basic_string<CharT> expected, std::basic_string<CharT> fmt,
     assert(
         std::equal(out.begin(), out.end(), expected.begin(), expected.end()));
   }
   {
     assert(expected.size() < 4096 && "Update the size of the buffer.");
     CharT out[4096];
     CharT* it = std::format_to(out, std::locale(), fmt, args...);
     assert(std::distance(out, it) == int(expected.size()));
-    *it = '\0';
-    assert(out == expected);
+    // Convert to std::string since output contains '\0' for boolean tests.
+    assert(std::basic_string<CharT>(out, it) == expected);
   }
 }
 
 template <class CharT, class... Args>
 void test_exception(std::string_view what, std::basic_string<CharT>(fmt),
                     const Args&... args) {
 #ifndef _LIBCPP_NO_EXCEPTIONS
   try {

libcxx/test/std/utilities/format/format.functions/format_to.pass.cpp

void test(std::basic_string<CharT> expected, std::basic_string<CharT> fmt,
     assert(
         std::equal(out.begin(), out.end(), expected.begin(), expected.end()));
   }
   {
     assert(expected.size() < 4096 && "Update the size of the buffer.");
     CharT out[4096];
     CharT* it = std::format_to(out, fmt, args...);
     assert(std::distance(out, it) == int(expected.size()));
-    *it = '\0';
-    assert(out == expected);
+    // Convert to std::string since output contains '\0' for boolean tests.
+    assert(std::basic_string<CharT>(out, it) == expected);
   }
 }
 
 template <class CharT, class... Args>
 void test_exception(std::string_view what, std::basic_string<CharT>(fmt),
                     const Args&... args) {
 #ifndef _LIBCPP_NO_EXCEPTIONS
   try {

libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp

void test(std::basic_string<CharT> expected, std::locale loc,
   }
   // *** formatted_size ***
   {
     size_t size = std::formatted_size(loc, fmt, args...);
     assert(size == expected.size());
   }
 }
 
+#ifndef _LIBCPP_HAS_NO_UNICODE
+template <class CharT>
+struct numpunct_unicode;
+
+template <>
+struct numpunct_unicode<char> : std::numpunct<char> {
+  string_type do_truename() const override { return "gültig"; }
+  string_type do_falsename() const override { return "ungültig"; }
+};
+
+template <>
+struct numpunct_unicode<wchar_t> : std::numpunct<wchar_t> {
+  string_type do_truename() const override { return L"gültig"; }
+  string_type do_falsename() const override { return L"ungültig"; }
+};
+#endif
+
+template <class CharT>
+void test_bool() {
+  std::locale loc = std::locale(std::locale(), new numpunct<CharT>());
+
+  std::locale::global(std::locale(LOCALE_en_US_UTF_8));
+  assert(std::locale().name() == LOCALE_en_US_UTF_8);
+  test(STR("true"), STR("{:L}"), true);
+  test(STR("false"), STR("{:L}"), false);
+
+  test(STR("yes"), loc, STR("{:L}"), true);
+  test(STR("yes"), loc, STR("{:L}"), true);
+
+  std::locale::global(loc);
+  test(STR("yes"), STR("{:L}"), true);
+  test(STR("no"), STR("{:L}"), false);
+
+  test(STR("true"), std::locale(LOCALE_en_US_UTF_8), STR("{:L}"), true);
+  test(STR("false"), std::locale(LOCALE_en_US_UTF_8), STR("{:L}"), false);
+
+#ifndef _LIBCPP_HAS_NO_UNICODE
+  std::locale loc_unicode =
+      std::locale(std::locale(), new numpunct_unicode<CharT>());
+
+  test(STR("gültig"), loc_unicode, STR("{:L}"), true);
+  test(STR("ungültig"), loc_unicode, STR("{:L}"), false);
+
+  test(STR("gültig!!!"), loc_unicode, STR("{:!<9L}"), true);
+  test(STR("_gültig__"), loc_unicode, STR("{:_^9L}"), true);
+  test(STR("   gültig"), loc_unicode, STR("{:>9L}"), true);
+#endif
+}
+
 template <class CharT>
 void test_integer() {
   std::locale loc = std::locale(std::locale(), new numpunct<CharT>());
   std::locale en_US = std::locale(LOCALE_en_US_UTF_8);
 
   // *** Decimal ***
   std::locale::global(en_US);
   test(STR("0"), STR("{:L}"), 0);
void test_integer() {
 
   test(STR("-00004_a"), loc, STR("{:08Lx}"), -0x4a);
   test(STR("-0x004_a"), loc, STR("{:#08Lx}"), -0x4a);
   test(STR("-0X004_A"), loc, STR("{:#08LX}"), -0x4a);
 }
 
 template <class CharT>
 void test() {
+  test_bool<CharT>();
   test_integer<CharT>();
 }
 
 int main(int, char**) {
   test<char>();
   test<wchar_t>();
 
   return 0;
 }

libcxx/test/std/utilities/format/format.functions/tests.inc

 //===----------------------------------------------------------------------===//
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 // Contains the test cases for the format functions. The locale-specific form
 // aren't tested in these test cases. They're tested in
 // locale-specific_form.pass.cpp.
 
 #define STR(S) MAKE_STRING(CharT, S)
+#define CSTR(S) MAKE_CSTRING(CharT, S)
 
 template <class CharT>
 std::vector<std::basic_string<CharT>> invalid_types(std::string valid) {
   std::vector<std::basic_string<CharT>> result;
 
 #define CASE(T)                                                                \
   case #T[0]:                                                                  \
     result.push_back(STR("Invalid formatter type {:" #T "}"));                 \
void test_string() {
   test_string<CharT>(world.c_str(), universe.c_str());
   test_string<CharT>(const_cast<CharT*>(world.c_str()),
                      const_cast<CharT*>(universe.c_str()));
   test_string<CharT>(std::basic_string_view<CharT>(world),
                      std::basic_string_view<CharT>(universe));
   test_string<CharT>(world, universe);
   test_string_unicode<CharT>();
 }
+template <class CharT>
+void test_bool() {
+
+  // *** align-fill & width ***
+  test(STR("answer is 'true   '"), STR("answer is '{:7}'"), true);
+  test(STR("answer is '   true'"), STR("answer is '{:>7}'"), true);
+  test(STR("answer is 'true   '"), STR("answer is '{:<7}'"), true);
+  test(STR("answer is ' true  '"), STR("answer is '{:^7}'"), true);
+
+  test(STR("answer is 'false   '"), STR("answer is '{:8s}'"), false);
+  test(STR("answer is '   false'"), STR("answer is '{:>8s}'"), false);
+  test(STR("answer is 'false   '"), STR("answer is '{:<8s}'"), false);
+  test(STR("answer is ' false  '"), STR("answer is '{:^8s}'"), false);
+
+  test(STR("answer is '---true'"), STR("answer is '{:->7}'"), true);
+  test(STR("answer is 'true---'"), STR("answer is '{:-<7}'"), true);
+  test(STR("answer is '-true--'"), STR("answer is '{:-^7}'"), true);
+
+  test(STR("answer is '---false'"), STR("answer is '{:->8s}'"), false);
+  test(STR("answer is 'false---'"), STR("answer is '{:-<8s}'"), false);
+  test(STR("answer is '-false--'"), STR("answer is '{:-^8s}'"), false);
+
+  // *** Sign ***
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:-}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:+}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{: }"),
+                 true);
+
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:-s}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:+s}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{: s}"),
+                 true);
+
+  // *** alternate form ***
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 STR("{:#}"), true);
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 STR("{:#s}"), true);
+
+  // *** zero-padding ***
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 STR("{:0}"), true);
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 STR("{:0s}"), true);
+
+  // *** precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.0}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.42}"), true);
+
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.s}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.0s}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.42s}"), true);
+
+  // *** locale-specific form ***
+  // See locale-specific_form.pass.cpp
+
+  // *** type ***
+  for (const auto& fmt : invalid_types<CharT>("bBcdosxX"))
+    test_exception(
+        "The format-spec type has a type not supported for a bool argument",
+        fmt, true);
+}
+
+template <class CharT>
+void test_bool_as_char() {
+  // *** align-fill & width ***
+  test(STR("answer is '\1     '"), STR("answer is '{:6c}'"), true);
+  test(STR("answer is '     \1'"), STR("answer is '{:>6c}'"), true);
+  test(STR("answer is '\1     '"), STR("answer is '{:<6c}'"), true);
+  test(STR("answer is '  \1   '"), STR("answer is '{:^6c}'"), true);
+
+  test(STR("answer is '-----\1'"), STR("answer is '{:->6c}'"), true);
+  test(STR("answer is '\1-----'"), STR("answer is '{:-<6c}'"), true);
+  test(STR("answer is '--\1---'"), STR("answer is '{:-^6c}'"), true);
+
+  test(std::basic_string<CharT>(CSTR("answer is '\0     '"), 18),
+       STR("answer is '{:6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '\0     '"), 18),
+       STR("answer is '{:6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '     \0'"), 18),
+       STR("answer is '{:>6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '\0     '"), 18),
+       STR("answer is '{:<6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '  \0   '"), 18),
+       STR("answer is '{:^6c}'"), false);
+
+  test(std::basic_string<CharT>(CSTR("answer is '-----\0'"), 18),
+       STR("answer is '{:->6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '\0-----'"), 18),
+       STR("answer is '{:-<6c}'"), false);
+  test(std::basic_string<CharT>(CSTR("answer is '--\0---'"), 18),
+       STR("answer is '{:-^6c}'"), false);
+
+  // *** Sign ***
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:-c}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{:+c}"),
+                 true);
+  test_exception("A sign field isn't allowed in this format-spec", STR("{: c}"),
+                 true);
+
+  // *** alternate form ***
+  test_exception("An alternate form field isn't allowed in this format-spec",
+                 STR("{:#c}"), true);
+
+  // *** zero-padding ***
+  test_exception("A zero-padding field isn't allowed in this format-spec",
+                 STR("{:0c}"), true);
+
+  // *** precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.c}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.0c}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.42c}"), true);
+
+  // *** locale-specific form ***
+  // Note it has no effect but it's allowed.
+  test(STR("answer is '*'"), STR("answer is '{:Lc}'"), '*');
+
+  // *** type ***
+  for (const auto& fmt : invalid_types<CharT>("bBcdosxX"))
+    test_exception(
+        "The format-spec type has a type not supported for a bool argument",
+        fmt, true);
+}
+
+template <class CharT>
+void test_bool_as_integer() {
+  // *** align-fill & width ***
+  test(STR("answer is '1'"), STR("answer is '{:<1d}'"), true);
+  test(STR("answer is '1 '"), STR("answer is '{:<2d}'"), true);
+  test(STR("answer is '0 '"), STR("answer is '{:<2d}'"), false);
+
+  test(STR("answer is '     1'"), STR("answer is '{:6d}'"), true);
+  test(STR("answer is '     1'"), STR("answer is '{:>6d}'"), true);
+  test(STR("answer is '1     '"), STR("answer is '{:<6d}'"), true);
+  test(STR("answer is '  1   '"), STR("answer is '{:^6d}'"), true);
+
+  test(STR("answer is '*****0'"), STR("answer is '{:*>6d}'"), false);
+  test(STR("answer is '0*****'"), STR("answer is '{:*<6d}'"), false);
+  test(STR("answer is '**0***'"), STR("answer is '{:*^6d}'"), false);
+
+  // Test whether zero padding is ignored
+  test(STR("answer is '     1'"), STR("answer is '{:>06d}'"), true);
+  test(STR("answer is '1     '"), STR("answer is '{:<06d}'"), true);
+  test(STR("answer is '  1   '"), STR("answer is '{:^06d}'"), true);
+
+  // *** Sign ***
+  test(STR("answer is 1"), STR("answer is {:d}"), true);
+  test(STR("answer is 0"), STR("answer is {:-d}"), false);
+  test(STR("answer is +1"), STR("answer is {:+d}"), true);
+  test(STR("answer is  0"), STR("answer is {: d}"), false);
+
+  // *** alternate form ***
+  test(STR("answer is +1"), STR("answer is {:+#d}"), true);
+  test(STR("answer is +1"), STR("answer is {:+b}"), true);
+  test(STR("answer is +0b1"), STR("answer is {:+#b}"), true);
+  test(STR("answer is +0B1"), STR("answer is {:+#B}"), true);
+  test(STR("answer is +1"), STR("answer is {:+o}"), true);
+  test(STR("answer is +01"), STR("answer is {:+#o}"), true);
+  test(STR("answer is +1"), STR("answer is {:+x}"), true);
+  test(STR("answer is +0x1"), STR("answer is {:+#x}"), true);
+  test(STR("answer is +1"), STR("answer is {:+X}"), true);
+  test(STR("answer is +0X1"), STR("answer is {:+#X}"), true);
+
+  test(STR("answer is 0"), STR("answer is {:#d}"), false);
+  test(STR("answer is 0"), STR("answer is {:b}"), false);
+  test(STR("answer is 0b0"), STR("answer is {:#b}"), false);
+  test(STR("answer is 0B0"), STR("answer is {:#B}"), false);
+  test(STR("answer is 0"), STR("answer is {:o}"), false);
+  test(STR("answer is 0"), STR("answer is {:#o}"), false);
+  test(STR("answer is 0"), STR("answer is {:x}"), false);
+  test(STR("answer is 0x0"), STR("answer is {:#x}"), false);
+  test(STR("answer is 0"), STR("answer is {:X}"), false);
+  test(STR("answer is 0X0"), STR("answer is {:#X}"), false);
+
+  // *** zero-padding & width ***
+  test(STR("answer is +00000000001"), STR("answer is {:+#012d}"), true);
+  test(STR("answer is +00000000001"), STR("answer is {:+012b}"), true);
+  test(STR("answer is +0b000000001"), STR("answer is {:+#012b}"), true);
+  test(STR("answer is +0B000000001"), STR("answer is {:+#012B}"), true);
+  test(STR("answer is +00000000001"), STR("answer is {:+012o}"), true);
+  test(STR("answer is +00000000001"), STR("answer is {:+#012o}"), true);
+  test(STR("answer is +00000000001"), STR("answer is {:+012x}"), true);
+  test(STR("answer is +0x000000001"), STR("answer is {:+#012x}"), true);
+  test(STR("answer is +00000000001"), STR("answer is {:+012X}"), true);
+  test(STR("answer is +0X000000001"), STR("answer is {:+#012X}"), true);
+
+  test(STR("answer is 000000000000"), STR("answer is {:#012d}"), false);
+  test(STR("answer is 000000000000"), STR("answer is {:012b}"), false);
+  test(STR("answer is 0b0000000000"), STR("answer is {:#012b}"), false);
+  test(STR("answer is 0B0000000000"), STR("answer is {:#012B}"), false);
+  test(STR("answer is 000000000000"), STR("answer is {:012o}"), false);
+  test(STR("answer is 000000000000"), STR("answer is {:#012o}"), false);
+  test(STR("answer is 000000000000"), STR("answer is {:012x}"), false);
+  test(STR("answer is 0x0000000000"), STR("answer is {:#012x}"), false);
+  test(STR("answer is 000000000000"), STR("answer is {:012X}"), false);
+  test(STR("answer is 0X0000000000"), STR("answer is {:#012X}"), false);
+
+  // *** precision ***
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.0}"), true);
+  test_exception("The format-spec should consume the input or end with a '}'",
+                 STR("{:.42}"), true);
+
+  // *** locale-specific form ***
+  // See locale-specific_form.pass.cpp
+
+  // *** type ***
+  for (const auto& fmt : invalid_types<CharT>("bBcdosxX"))
+    test_exception(
+        "The format-spec type has a type not supported for a bool argument",
+        fmt, true);
+}
 
 template <class I, class CharT>
 void test_integer_as_integer() {
   // *** align-fill & width ***
   test(STR("answer is '42'"), STR("answer is '{:<1}'"), I(42));
   test(STR("answer is '42'"), STR("answer is '{:<2}'"), I(42));
   test(STR("answer is '42 '"), STR("answer is '{:<3}'"), I(42));
 

 
 template <class CharT>
 void test() {
   // *** Test escaping  ***
   test(STR("{"), STR("{{"));
   test(STR("}"), STR("}}"));
 
   // *** Test argument ID ***
-  test(STR("hello 01"), STR("hello {0:}{1:}"), false, true);
-  test(STR("hello 10"), STR("hello {1:}{0:}"), false, true);
+  test(STR("hello false true"), STR("hello {0:} {1:}"), false, true);
+  test(STR("hello true false"), STR("hello {1:} {0:}"), false, true);
 
   // ** Test invalid format strings ***
   test_exception("The format string terminates at a '{'", STR("{"));
   test_exception("The replacement field misses a terminating '}'", STR("{:"),
                  42);
 
   test_exception("The format string contains an invalid escape sequence",
                  STR("}"));
void test() {
   {
     std::basic_string<CharT> buffer = STR("world");
     std::basic_string_view<CharT> data = buffer;
     test(STR("hello world"), STR("hello {}"), data);
   }
   test_string<CharT>();
 
   // *** Test Boolean format argument ***
-  test(STR("hello 01"), STR("hello {}{}"), false, true);
+  test(STR("hello false true"), STR("hello {} {}"), false, true);
+
+  test_bool<CharT>();
+  test_bool_as_char<CharT>();
+  test_bool_as_integer<CharT>();
 
   // *** Test signed integral format argument ***
   test(STR("hello 42"), STR("hello {}"), static_cast<signed char>(42));
   test(STR("hello 42"), STR("hello {}"), static_cast<short>(42));
   test(STR("hello 42"), STR("hello {}"), static_cast<int>(42));
   test(STR("hello 42"), STR("hello {}"), static_cast<long>(42));
   test(STR("hello 42"), STR("hello {}"), static_cast<long long>(42));
 #ifndef _LIBCPP_HAS_NO_INT128

libcxx/test/std/utilities/format/format.functions/vformat_to.locale.pass.cpp

void test(std::basic_string<CharT> expected, std::basic_string<CharT> fmt,
   {
     assert(expected.size() < 4096 && "Update the size of the buffer.");
     CharT out[4096];
     CharT* it = std::vformat_to(
         out, std::locale(), fmt,
         std::make_format_args<std::basic_format_context<CharT*, CharT>>(
             args...));
     assert(std::distance(out, it) == int(expected.size()));
-    *it = '\0';
-    assert(out == expected);
+    // Convert to std::string since output contains '\0' for boolean tests.
+    assert(std::basic_string<CharT>(out, it) == expected);
   }
 }
 
 template <class CharT, class... Args>
 void test_exception(std::string_view what, std::basic_string<CharT>(fmt),
                     const Args&... args) {
 #ifndef _LIBCPP_NO_EXCEPTIONS
   try {

libcxx/test/std/utilities/format/format.functions/vformat_to.pass.cpp

void test(std::basic_string<CharT> expected, std::basic_string<CharT> fmt,
   {
     assert(expected.size() < 4096 && "Update the size of the buffer.");
     CharT out[4096];
     CharT* it = std::vformat_to(
         out, fmt,
         std::make_format_args<std::basic_format_context<CharT*, CharT>>(
             args...));
     assert(std::distance(out, it) == int(expected.size()));
-    *it = '\0';
-    assert(out == expected);
+    // Convert to std::string since output contains '\0' for boolean tests.
+    assert(std::basic_string<CharT>(out, it) == expected);
   }
 }
 
 template <class CharT, class... Args>
 void test_exception(std::string_view what, std::basic_string<CharT>(fmt),
                     const Args&... args) {
 #ifndef _LIBCPP_NO_EXCEPTIONS
   try {