python@3.13.5.arm64_sequoia: `os.getlogin()` fails with `OSError: [Errno 34]` for usernames > 9 characters

[rstanevich]

brew gist-logs <formula> link OR brew config AND brew doctor output

brew config
HOMEBREW_VERSION: 4.5.6-71-ge3ae002-dirty
ORIGIN: https://github.com/Homebrew/brew
HEAD: e3ae002054e2069987757ee75baa9a03420a6da5
Last commit: 4 hours ago
Branch: master
Core tap JSON: 13 Jun 21:13 UTC
Core cask tap JSON: 13 Jun 21:13 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_AUTO_UPDATE_SECS: 180
HOMEBREW_CASK_OPTS: []
HOMEBREW_MAKE_JOBS: 10
HOMEBREW_SORBET_RUNTIME: set
Homebrew Ruby: 3.4.4 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.4.4/bin/ruby
CPU: deca-core 64-bit arm_firestorm_icestorm
Clang: 17.0.0 build 1700
Git: 2.39.5 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 15.5-arm64
CLT: 16.4.0.0.1.1747106510
Xcode: N/A
Rosetta 2: false

Verification

• My brew doctor output says Your system is ready to brew. and am still able to reproduce my issue.
• I ran brew update and am still able to reproduce my issue.
• I have resolved all warnings from brew doctor and that did not fix my problem.
• I searched for recent similar issues at https://github.com/Homebrew/homebrew-core/issues?q=is%3Aissue and found no duplicates.

What were you trying to do (and why)?

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

What happened (include all command output)?

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

---

Hypothesys:
This may be due to changes in https://github.com/python/cpython/pull/132751/files
So if python is compiled in an environment without HAVE_GETLOGIN_R but with HAVE_UT_NAMESIZE - getlogin_r will return error 34 if username is >9 characters

What did you expect to happen?

os.getlogin() is functioning

Step-by-step reproduction instructions (by running brew commands)

brew install python@3.13
# On a macOS Sequoia, be logged in as a user with a long name (>9 characters), for example, testuser123
python3 -c "import os; print(os.getlogin())

---

So I'm wondering if this issue can be resolved by changing the build environment settings?

[Bo98]

Looks like that pull request has a typo: https://github.com/python/cpython/blob/6eb6c5dbfb528bd07d77b60fd71fd05d81d45c41/configure.ac#L5545

sys/params.h should instead be sys/param.h

[alebcay]

Thanks for bringing this up, I've opened an issue upstream for this. In the meanwhile, we could possibly consider:

• Setting the configure flag ourselves (-DHAVE_MAXLOGNAME or something like that)
• Patching the configure script directly
• Waiting

[Bo98]

It's HAVE_MAXLOGNAME that's the problem rather than HAVE_GETLOGIN_R, but otherwise yeah ideally we'd apply an (upstreamed) patch.