gh-158893: Make os.strerror() thread-safe

[vstinner]

Make os.strerror() thread-safe: use the reentrant strerror_r() function if available.

• The configure script now checks if strerror_r() is supported.
• Add a stress test to test_free_threading.test_os (new module).
• Add a comment on decode_current_locale() assertion which fails if the input string is mutated.
• Add an assertion to _Py_DecodeLocale() to detect if the input string was mutated during the function call.

• Issue: Calling os.strerror() in parallel is not thread safe on FreeBSD #158893

[vstinner]

The test depends on PR #158926. Without the second PR, the test is always skipped.

[vstinner]

Oh. Build fails on Android. It seems like Android C library (bionic) uses the GNU API for strerror_r().

  ../../Modules/posixmodule.c:13953:9: error: incompatible pointer to integer conversion initializing 'int' with an expression of type 'char * _Nonnull' [-Wint-conversion]
   13953 |     int len = strerror_r(code, small_buffer, buflen);
         |         ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ../../Modules/posixmodule.c:13973:17: error: incompatible pointer to integer conversion assigning to 'int' from 'char * _Nonnull' [-Wint-conversion]
   13973 |             len = strerror_r(code, buffer, buflen);
         |                 ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[vstinner]

I clicked on [Update branch] to retrieve the sysconfig change, to run the test on Free Threaded builds.

[vstinner]

!buildbot FreeBSD15 NoGIL

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @vstinner for commit 7d18e20 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F158927%2Fmerge

The command will test the builders whose names match following regular expression: FreeBSD15 NoGIL

The builders matched are:

• AMD64 FreeBSD15 NoGIL PR

[vstinner]

buildbot/AMD64 FreeBSD15 NoGIL PR

The build https://buildbot.python.org/#/builders/2369/builds/1 failed because of test_free_threading.test_capi which is unrelated to this change, and I wrote #158935 to fix this test.

The test passed successfully! 0:08:38 load avg: 4.04 mem: 453.2 MiB [345/559] test.test_free_threading.test_os passed.

I ran manually test_free_threading.test_os on the main branch on Free Threading on FreeBSD 15: the test crashed as expected. So the test covers well the modified code.

[miss-islington-app]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @vstinner, I could not cleanly backport this to 3.15 due to a conflict.

Please backport manually with cherry_picker, see the devguide for more information.

cherry_picker 6318730aeebdf7282fa9a18aca52af4e87c0c39d 3.15

[miss-islington-app]

Sorry, @vstinner, I could not cleanly backport this to 3.14 due to a conflict.

Please backport manually with cherry_picker, see the devguide for more information.

cherry_picker 6318730aeebdf7282fa9a18aca52af4e87c0c39d 3.14

[vstinner]

I will backport the fix to 3.14 and 3.15 branches once the 3.15 branch will be unblocked (next week). Right now, there are too many backports to 3.15 in the queue.