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

vstinner · 2023-09-06T13:38:48Z

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.

Issue: Add FreeBSD build and test using Cirrus-CI #91960

vstinner · 2023-09-06T13:48:48Z

Without my PR, test on FreeBSD 13.2 with clang version 14.0.5: FAILURE

git clean -fdx; ./configure --with-pydebug && make clean && make && ./python -m test -v test_gdb -u all
Total tests: run=46 failures=4 skipped=9

Tests with my PR.

Linux, clang 16

Test on Linux, Fedora 38 with clang version 16.0.6 (Fedora 16.0.6-2.fc38):

clang -Og: SUCCESS with... 41 skipped tests on 46 :-)
- git clean -fdx; ./configure --with-pydebug && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=41
clang -O0: SUCCESS with only 1 test skipped!
- git clean -fdx; ./configure --with-pydebug CFLAGS="-O0" && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=1
- test_print_after_up() is skipped because of: "Unable to read information on python frame"

FreeBSD, clang 14

Test on FreeBSD 13.2 with clang version 14.0.5:

clang -Og: SUCCESS with... 41 skipped tests on 46 :-)
- git clean -fdx; ./configure --with-pydebug && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=41
clang -O0: SUCCESS with only 1 test skipped!
git clean -fdx; ./configure --with-pydebug CFLAGS="-O0" && make clean && make && ./python -m test -v test_gdb -u all
Total tests: run=46 skipped=1

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.

vstinner · 2023-09-06T13:51:30Z

UPDATE: Moreover, test_gdb is no longer skipped on macOS if Python is built with Clang.

diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py
index c05a2d387c..ca50574e46 100644
--- a/Lib/test/test_gdb.py
+++ b/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 '')):

vstinner · 2023-09-06T14:10:19Z

Test with my PR and clang -O3.

Test on Linux: SUCCESS with only 18 skipped tests on 46, nice!

git clean -fdx; ./configure --with-pydebug CC=clang && make clean && make && ./python -m test -v test_gdb -u all
Total tests: run=46 skipped=18

Test on FreeBSD: SUCCESS with only 18 skipped tests on 46, nice!

git clean -fdx; ./configure && make clean && make && ./python -m test -v test_gdb -u all
Total tests: run=46 skipped=18

vstinner · 2023-09-06T14:17:03Z

Now I have doubts about my tests on Linux :-( I'm not sure that I passed CC=clang to configure!

I redone my tests on Linux:

clang -O0: SUCCESS
- git clean -fdx; ./configure CC=clang -with-pydebug CFLAGS="-O0" && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=1
- grep -E '^(CC=|OPT=)' Makefile: CC=clang and OPT=-g -Og -Wall
clang -Og: SUCCESS
- git clean -fdx; ./configure CC=clang -with-pydebug && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=41
- grep -E '^(CC=|OPT=)' Makefile: CC=clang and OPT=-g -Og -Wall
clang -O3: SUCCESS
- git clean -fdx; ./configure CC=clang && make clean && make && ./python -m test -v test_gdb -u all
- Total tests: run=46 skipped=18
- grep -E '^(CC=|OPT=)' Makefile: CC=clang and OPT=-DNDEBUG -g -O3 -Wall

Oh ok, we are safe :-)

vstinner · 2023-09-06T14:20:02Z

GitHub Action jobs:

Ubuntu: test_gdb passed, Python is built with gcc -g -Og
Address sanitizer: "test_gdb passed", Python is built with gcc -DNDEBUG -g -O3
macOS: test_gdb skipped -- Couldn't find gdb on the path

emaste · 2023-09-06T14:32:42Z

Clang just treats -Og as an alias for -O1, so it's not surprising that the debuginfo quality is not as good as GCC's.
llvm/llvm-project@d340ccc

sorcio · 2023-09-06T14:40:08Z

Lib/test/test_gdb.py

@@ -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)',


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.

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.

miss-islington · 2023-09-06T14:51:16Z

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington · 2023-09-06T14:51:16Z

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

…thonGH-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. (cherry picked from commit fbce43a) Co-authored-by: Victor Stinner <[email protected]>

bedevere-bot · 2023-09-06T14:51:29Z

GH-109010 is a backport of this pull request to the 3.12 branch.

…thonGH-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. (cherry picked from commit fbce43a) Co-authored-by: Victor Stinner <[email protected]>

bedevere-bot · 2023-09-06T14:51:33Z

GH-109011 is a backport of this pull request to the 3.11 branch.

…H-108999) (#109011) gh-91960: Skip test_gdb if gdb cannot retrive Python frames (GH-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. (cherry picked from commit fbce43a) Co-authored-by: Victor Stinner <[email protected]>

vstinner · 2023-09-07T04:10:58Z

Sadly, this change wasn't enough to fix PPC64LE Fedora Stable Clang 3.x: I created issue #109053.

…H-108999) (#109010) gh-91960: Skip test_gdb if gdb cannot retrive Python frames (GH-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. (cherry picked from commit fbce43a) Co-authored-by: Victor Stinner <[email protected]>

bedevere-bot added awaiting core review tests Tests in the Lib/test dir labels Sep 6, 2023

bedevere-bot mentioned this pull request Sep 6, 2023

Add FreeBSD build and test using Cirrus-CI #91960

Closed

vstinner force-pushed the test_gdb_clang branch from 542c061 to 66a5f76 Compare September 6, 2023 13:50

This was referenced Sep 6, 2023

gh-91960: skip test_gdb when built with clang #108993

Closed

gh-91960: Add FreeBSD build and test using Cirrus-CI #91961

Merged

emaste approved these changes Sep 6, 2023

View reviewed changes

vstinner enabled auto-merge (squash) September 6, 2023 14:24

vstinner merged commit fbce43a into python:main Sep 6, 2023
17 checks passed

vstinner deleted the test_gdb_clang branch September 6, 2023 14:34

bedevere-bot removed the awaiting core review label Sep 6, 2023

sorcio reviewed Sep 6, 2023

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vstinner added needs backport to 3.11 only security fixes needs backport to 3.12 bug and security fixes labels Sep 6, 2023

bedevere-bot removed the needs backport to 3.12 bug and security fixes label Sep 6, 2023

bedevere-bot removed the needs backport to 3.11 only security fixes label Sep 6, 2023

vstinner mentioned this pull request Sep 7, 2023

test_gdb fails on PPC64LE Fedora Stable Clang 3.x buildbot #109053

Closed

sorcio mentioned this pull request Sep 11, 2023

Have debug builds support gdb extension by default #109270

Closed

vstinner mentioned this pull request Sep 13, 2023

PPC64LE Fedora Stable Clang 3.x fails test_gdb #104736

Closed

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

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 #108999

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

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vstinner commented Sep 6, 2023 • edited by bedevere-bot Loading

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Linux, clang 16

FreeBSD, clang 14

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