os.getlogin() fails with OSError: [Errno 34] for usernames > 9 characters

[alebcay]

Bug report

Bug description:

import os
print(os.getlogin())

$ python3 -c "import os; print(os.getlogin())"

Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import os; print(os.getlogin())
                     ~~~~~~~~~~~^^
OSError: [Errno -34] Unknown error: -34

It appears that if Python is compiled in an environment without HAVE_MAXLOGNAME but with HAVE_UT_NAMESIZE, getlogin_r will return error 34 if username is >9 characters.

This appears to be a regression introduced in #132751:

https://github.com/duaneg/cpython/blob/675342cf59ffe53337d92af989b97dad687a10ea/configure.ac#L5434

The correct header file to search for is sys/param.h, not sys/params.h. As a result, HAVE_UT_NAMESIZE is satisfied (via utmp.h) but HAVE_MAXLOGNAME is not.

This was originally reported to Homebrew via Homebrew/homebrew-core#226857.

CPython versions tested on:

3.15

Operating systems tested on:

macOS

Linked PRs

• gh-135497: fix MAXLOGNAME detection in configure #135508
• [3.14] gh-135497: fix MAXLOGNAME detection in configure.ac (GH-135508) #135516
• [3.13] gh-135497: fix MAXLOGNAME detection in configure.ac (GH-135508) #135517

[sobolevn]

@alebcay would you like to submit a PR with the fix?

[alebcay]

Sure, I'd be happy to. As far as processes go, should I also regenerate configure, and is there a particular command/script I should use for that? I found https://devguide.python.org/contrib/workflows/regenerate/#regenerate-configure and will use that.