gh-91960: Skip test_gdb if gdb cannot retrive Python frames (#108999)

Skip test_gdb if gdb is unable to retrieve Python frame objects: if a
frame is "<optimized out>". When Python is built with "clang -Og",
gdb can fail to retrive the 'frame' parameter of
_PyEval_EvalFrameDefault(). In this case, tests like py_bt() are
likely to fail. Without getting access to Python frames,
python-gdb.py is mostly clueless on retrieving the Python traceback.
Moreover, test_gdb is no longer skipped on macOS if Python is built
with Clang.

Author: vstinner

Lib/test/test_gdb.py

@@ -55,10 +55,6 @@ def get_gdb_version():
 if not sysconfig.is_python_build():
     raise unittest.SkipTest("test_gdb only works on source builds at the moment.")
 
-if 'Clang' in platform.python_compiler() and sys.platform == 'darwin':
-    raise unittest.SkipTest("test_gdb doesn't work correctly when python is"
-                            " built with LLVM clang")
-
 if ((sysconfig.get_config_var('PGO_PROF_USE_FLAG') or 'xxx') in
     (sysconfig.get_config_var('PY_CORE_CFLAGS') or '')):
     raise unittest.SkipTest("test_gdb is not reliable on PGO builds")
@@ -247,6 +243,9 @@ def get_stack_trace(self, source=None, script=None,
         for pattern in (
             '(frame information optimized out)',
             'Unable to read information on python frame',
+            # gh-91960: On Python built with "clang -Og", gdb gets
+            # "frame=<optimized out>" for _PyEval_EvalFrameDefault() parameter
+            '(unable to read python frame information)',
         ):
             if pattern in out:
                 raise unittest.SkipTest(f"{pattern!r} found in gdb output")

Misc/NEWS.d/next/Tests/2023-09-06-15-36-51.gh-issue-91960.P3nD5v.rst

@@ -0,0 +1,7 @@
+Skip ``test_gdb`` if gdb is unable to retrieve Python frame objects: if a
+frame is ``<optimized out>``. When Python is built with "clang -Og", gdb can
+fail to retrive the *frame* parameter of ``_PyEval_EvalFrameDefault()``. In
+this case, tests like ``py_bt()`` are likely to fail. Without getting access
+to Python frames, ``python-gdb.py`` is mostly clueless on retrieving the
+Python traceback. Moreover, ``test_gdb`` is no longer skipped on macOS if
+Python is built with Clang. Patch by Victor Stinner.