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

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Merged
vstinner merged 1 commit into from
Sep 6, 2023
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gh-91960: Skip test_gdb if gdb cannot retrive Python frames #108999

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gh-91960: Skip test_gdb if gdb cannot retrive Python frames 
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.
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@vstinner
vstinner committed Sep 6, 2023
commit 66a5f76ed50a79aa5d1b0ac484ee06491716606b
7 changes: 3 additions & 4 deletions Lib/test/test_gdb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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")
Expand Down Expand Up @@ -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)',

@sorcio sorcio Sep 6, 2023

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Any idea why libpython.py prints this rather than "Unable to read information on python frame"? It's possible that there are just some spots that you missed back in #19081

I'm also afraid that this speaks of a fragility of this approach. When optimizations are enabled, it's not easy to predict exactly what is going to be missing. But I'm happy that this allows to re-enable tests on platforms that were entirely ignored.

@vstinner vstinner Sep 6, 2023

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Any idea why libpython.py prints this rather than "Unable to read information on python frame"? It's possible that there are just some spots that you missed back in #19081

It's likely possible to unify python-gdb.py logs, or use a different regex to match both cases :-) The (unable to read ...) format is for py-bt command. Depending on the command, the log is displayed differently. I took the lazy way of just matching the two strings.

):
if pattern in out:
raise unittest.SkipTest(f"{pattern!r} found in gdb output")
Expand Down
7 changes: 7 additions & 0 deletions Misc/NEWS.d/next/Tests/2023-09-06-15-36-51.gh-issue-91960.P3nD5v.rst
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@@ -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.