test_capi crash and produce core dumps on FreeBSD 13

[vstinner]

Examples:

[vstinner@freebsd ~/python/main]$ ./python -m test test_capi -m test_no_FatalError_infinite_loop -v
...
Warning -- files was modified by test_capi
Warning --   Before: []
Warning --   After:  ['python.core'] 

and

[vstinner@freebsd ~/python/main]$ ./python -m test -v test_capi -m test_get_set_optimizer 
...
test_get_set_optimizer (test.test_capi.test_misc.TestOptimizerAPI.test_get_set_optimizer) ... Fatal Python error: Segmentation fault

Current thread 0x0000000827265000 (most recent call first):
  File "/usr/home/vstinner/python/main/Lib/unittest/case.py", line 589 in _callTestMethod
  File "/usr/home/vstinner/python/main/Lib/unittest/case.py", line 634 in run
  File "/usr/home/vstinner/python/main/Lib/unittest/case.py", line 690 in __call__
  File "/usr/home/vstinner/python/main/Lib/unittest/suite.py", line 122 in run

• FreeBSD 13.2-RELEASE-p1
• clang 14.0.5
• Python configured with: ./configure --cache-file=../config.cache --with-pydebug CFLAGS="-O0"

Linked PRs

• gh-106714: Fix test_capi to not write a coredump #107007
• [3.12] gh-106714: Fix test_capi to not write a coredump (GH-107007) #107009

[vstinner]

Oh, AArch64 Fedora Rawhide buildbot has the same failure: it also produces a coredump.

This issue affects operating systems configured to write a coredump in the current directory if a process does crash. Example on the AArch64 Fedora Rawhide machine:

$ cat /proc/sys/kernel/core_pattern 
[vstinner@python-builder-fedora-rawhide-aarch64 ~]$ file /proc/sys/kernel/core_pattern 
/proc/sys/kernel/core_pattern: empty
[vstinner@python-builder-fedora-rawhide-aarch64 test]$ cat /proc/sys/kernel/core_uses_pid 
1

[vstinner@python-builder-fedora-rawhide-aarch64 test]$ ulimit -c
unlimited

[vstinner@python-builder-fedora-rawhide-aarch64 ~]$ mkdir test
[vstinner@python-builder-fedora-rawhide-aarch64 ~]$ cd test
[vstinner@python-builder-fedora-rawhide-aarch64 test]$ python
Python 3.11.3 (main, Apr  5 2023, 00:00:00) [GCC 13.0.1 20230404 (Red Hat 13.0.1-0)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ctypes
>>> ctypes.string_at(0)
Segmentation fault (core dumped)

[vstinner@python-builder-fedora-rawhide-aarch64 test]$ ls -la
(...)
-rw-------.  1 vstinner vstinner 9465856 Jul 22 13:45 .2755244

A core dump named .2755244 was created in the current directory.

[vstinner]

Oh, this bug is a recent regression introduced by #102729

[vstinner]

Python 3.11 is not affected:

    @support.requires_subprocess()
    def test_no_FatalError_infinite_loop(self):
        with support.SuppressCrashReport():
            p = subprocess.Popen([sys.executable, "-c",
                                  'import _testcapi;'
                                  '_testcapi.crash_no_current_thread()'],
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE)
        (out, err) = p.communicate()