[lldb/Test] Fix ASan/TSan workaround for Xcode Python 3

[JDevlieghere]

Summary

The Python 3 interpreter in Xcode has a relative RPATH and dyld fails to load it when we copy it into the build directory. Provide a workaround for the workaround...

dyld: Library not loaded: @executable_path/../../../../Python3
  Referenced from: /Users/jonas/llvm/build-tsan/lldb-test-build.noindex/copied-python
  Reason: image not found

[JDevlieghere]

Avoid a race that would result in another test finding the copied python before it has been tested.

[JDevlieghere]

Fix typo

[JDevlieghere]

Move work out of LLDBTest so we only have to compute it once.

[vsk]

lldb/test/API/lit.cfg.py

56 ↗

(On Diff #270262)

This isn't relevant for the unit or shell tests because the API tests are the only ones that are executed within a python process, right?

58 ↗

(On Diff #270262)

Is the part about synchronization still applicable? Maybe it is, if you run llvm-lit test/API from two different directories?

102 ↗

(On Diff #270262)

What does setting python_executable do? I looked this up in llvm and found:

test/lit.cfg.py:    ('%llvm-locstats', "'%s' %s" % (config.python_executable, llvm_locstats_tool)))
test/lit.site.cfg.py.in:config.python_executable = "@PYTHON_EXECUTABLE@"
test/tools/UpdateTestChecks/lit.local.cfg:            config.python_executable, script_path, extra_args)))

Am I missing something, or does something here translate into a lit directive to run python files under python_interpreter?

[JDevlieghere]

lldb/test/API/lit.cfg.py

56 ↗

(On Diff #270262)

Correct.

58 ↗

(On Diff #270262)

I guess it is, but not something I'd optimize for. I'll remove the comment.

102 ↗

(On Diff #270262)

test/lit.site.cfg.py.in will be configured with the path to the real python executable in the build dir.

[vsk]

Lgtm, thanks.

lldb/test/API/lit.cfg.py

102 ↗

(On Diff #270262)

This is what I was missing: lldb/test/API/lldbtest.py: executable = test.config.python_executable.

lldb/test/API/lldbtest.py

113

.. so by the time this is reached, executable should point to a known-good python binary.

[JDevlieghere]

lldb/test/API/lldbtest.py

113

Yep!

lldb/test/API/lldbtest.py

def mkdir_p(path):
     try:
         os.makedirs(path)
     except OSError as e:
         if e.errno != errno.EEXIST:
             raise
     if not os.path.isdir(path):
         raise OSError(errno.ENOTDIR, "%s is not a directory"%path)
 
+# On macOS, we can't do the DYLD_INSERT_LIBRARIES trick with a shim python
+# binary as the ASan interceptors get loaded too late. Also, when SIP is
+# enabled, we can't inject libraries into system binaries at all, so we need a
+# copy of the "real" python to work with.
+def get_darwin_python_interpreter(builddir, executable):
+    # Avoid doing any work if we already copied the binary. This serves as
+    # synchronization between multiple API tests.
+    copied_python = os.path.join(builddir, 'copied-python')
+    if os.path.isfile(copied_python):
+        return copied_python
+
+    # Find the "real" python binary.
+    import shutil, subprocess
+    real_python = subprocess.check_output([
+        executable,
+        os.path.join(os.path.dirname(os.path.realpath(__file__)),
+                     'get_darwin_real_python.py')
+    ]).decode('utf-8').strip()
+
+    # Copy over the real python to a temporary python. We can't put it in the
+    # right place yet, because that might race with other tests running
+    # concurrently.
+    temp_python = os.path.join(builddir, 'copied-python')
+    shutil.copy(real_python, temp_python)
+
+    # Now make sure the copied Python works. The Python in Xcode has a relative
+    # RPATH and cannot be copied.
+    try:
+        # We don't care about the output, just make sure it runs.
+        subprocess.check_output([temp_python, '-V'],
+                                stderr=subprocess.STDOUT)
+    except subprocess.CalledProcessError:
+        # The copied Python didn't work. Assume we're dealing with the Python
+        # interpreter in Xcode. Given that this is not a system binary SIP
+        # won't prevent us form injecting the interceptors so we get away
+        # without using the copy.
+        return real_python
+
+    # The copied Python works. Time to put it in place and start using it from
+    # now on.
+    shutil.copy(temp_python, copied_python)
+    return copied_python
+
+
 class LLDBTest(TestFormat):
     def __init__(self, dotest_cmd):
         self.dotest_cmd = dotest_cmd
 
     def getTestsInDirectory(self, testSuite, path_in_suite, litConfig,
                             localConfig):
         source_path = testSuite.getSourcePath(path_in_suite)
         for filename in os.listdir(source_path):
def execute(self, test, litConfig):
 
         if test.config.unsupported:
             return (lit.Test.UNSUPPORTED, 'Test is unsupported')
 
         testPath, testFile = os.path.split(test.getSourcePath())
 
         # The Python used to run lit can be different from the Python LLDB was
         # build with.
         executable = test.config.python_executable
 
         # On Windows, the system does not always correctly interpret
         # shebang lines.  To make sure we can execute the tests, add
         # python exe as the first parameter of the command.
         cmd = [executable] + self.dotest_cmd + [testPath, '-p', testFile]
 
         builddir = getBuildDir(cmd)
         mkdir_p(builddir)
-
-        # On macOS, we can't do the DYLD_INSERT_LIBRARIES trick with a shim
-        # python binary as the ASan interceptors get loaded too late. Also,
-        # when SIP is enabled, we can't inject libraries into system binaries
-        # at all, so we need a copy of the "real" python to work with.
-        #
-        # Find the "real" python binary, copy it, and invoke it.
         if 'DYLD_INSERT_LIBRARIES' in test.config.environment and \
                 platform.system() == 'Darwin':
-            copied_python = os.path.join(builddir, 'copied-system-python')
-            if not os.path.isfile(copied_python):
-                import shutil, subprocess
-                python = subprocess.check_output([
-                    executable,
-                    os.path.join(os.path.dirname(os.path.realpath(__file__)),
-                        'get_darwin_real_python.py')
-                ]).decode('utf-8').strip()
-                shutil.copy(python, copied_python)
-            cmd[0] = copied_python
+            cmd[0] = get_darwin_python_interpreter(builddir, executable)
 
         if 'lldb-repro-capture' in test.config.available_features or \
            'lldb-repro-replay' in test.config.available_features:
             reproducer_root = os.path.join(builddir, 'reproducers')
             mkdir_p(reproducer_root)
             reproducer_path = os.path.join(reproducer_root, testFile)
             if 'lldb-repro-capture' in test.config.available_features:
                 cmd.extend(['--capture-path', reproducer_path])