gh-145335: Fix os functions when passing fd -1 as path

[vstinner]

os.listdir(-1) and os.scandir(-1) now fail with OSError(errno.EBADF) rather than listing the current directory.

os.listxattr(-1) now fails with OSError(errno.EBADF) rather than listing extended attributes of the current directory.

• Issue: Segfault from running os.pathconf(-1, 1) #145335

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @vstinner for commit a894262 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F145439%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[vstinner]

Tests failed on 5 buildbots, but failures are unrelated to this change.

buildbot/AMD64 CentOS9 NoGIL Refleaks PR

FAIL: test_free_reference (test.test_concurrent_futures.test_thread_pool.ThreadPoolExecutorTest.test_free_reference)

buildbot/AMD64 Fedora Stable Clang Installed PR
buildbot/PPC64LE Fedora Stable Clang Installed PR
buildbot/s390x Fedora Stable Clang Installed PR
buildbot/x86 Debian Installed with X PR

3 tests failed: test_datetime test_import test_interpreters. It should be fixed by commit 46c5c57.

[vstinner]

The PR is now ready for review.

cc @picnixz@aisk

[picnixz]

LGTM! Are there actually other places where we use the path converter and that would be useful? (that is, do you plan to look at other modules as follow-up?)

[vstinner]

Merged. Thanks for the review!

[vstinner]

@picnixz:

Are there actually other places where we use the path converter and that would be useful? (that is, do you plan to look at other modules as follow-up?)

I had a look and I didn't find other places with the same bug.

• path_converter() and path_t are specific to posixmodule.c.
• PyObject_AsFileDescriptor() fails with ValueError if the file descriptor is negative, so check for errors using fd == -1 or fd < 0 is correct.
• _PyLong_FileDescriptor_Converter() calls PyObject_AsFileDescriptor().
• Argument Clinic generates PyObject_AsFileDescriptor() calls when using fildes type.
• open() calls FileIO() which also explicitly rejects negative file descriptors.

[freakboy3742]

This appears to have broken Emscripten builds; not sure if the fix is a test skip, or if there's some additional handling required.

/cc @hoodmane

[hoodmane]

I'll look into it, thanks for the ping @freakboy3742.

[hoodmane]

Problem seems to be that on Emscripten execve is "supported" but always returns ENOEXEC.

[hoodmane]

Fix here: #145528

[vstinner]

This appears to have broken Emscripten builds; not sure if the fix is a test skip, or if there's some additional handling required.

Oh, I missed this buildbot failure since it's still classified as Unstable. I propose to promote it to Stable: python/buildmaster-config#678.