Thanks @jaraco for your comment.

To your first point: the changes to distutils.sysconfig are limited to the customize_compiler function, which is not available in the stdlib sysconfig, so although I'm admittedly not very familiar with the internals of distutils.sysconfig and sysconfig, I imagine that this change wouldn't have any impact on the effort involved in migrating from one to the other.

To your second point: I believe this patch was originally authored and published as part of a now 19-year-old bug filed against CPython, and the comments there (and the linked setuptools issue) might provide some insight into the rationale behind it and the issues that people are currently running into. The final suggestion there is to reopen against setuptools/distutils, and I'm not sure if there's been any followup since. The issue I have specifically been running into is probably niche and limited to Darwin platforms (I could do a more detailed writeup if that's helpful), but it seems that there's other scenarios where C++ support is wanted.

That said, while I've looked at the patch and it seems straightforward enough, I can't directly endorse it, and there's certainly improvements that could be made like you suggested. The primary argument I would make in favor of still including it as-is is simply 1) that it fixes a current pain point, and 2) that it is used by the entire nix ecosystem without any apparent problems.

I swear the tests were passing with this change, but after merging it, tests are failing (https://github.com/pypa/distutils/actions/runs/7889130804/job/21528245684). Two of those failures were just style nitpicks, fixed in 0e57a23. The other two are:

>       assert comp.exes['compiler'] == 'env_cc --sc-cflags --env-cflags --env-cppflags'
E       AssertionError: assert 'env_cc --env...-env-cppflags' == 'env_cc --sc-...-env-cppflags'
E         
E         - env_cc --sc-cflags --env-cflags --env-cppflags
E         ?       ------------
E         + env_cc --env-cflags --env-cppflags

distutils/tests/test_sysconfig.py:132: AssertionError

and

>           assert call_args[:4] == expected
E           AssertionError: assert ['my_cxx', 'g...'-o', 'a.out'] == ['my_cxx', '-...namic_lookup']
E             
E             At index 1 diff: 'gcc-4.2' != '-bundle'
E             Use -v to get more diff

distutils/tests/test_unixccompiler.py:276: AssertionError

I've force-pushed main without this merge and re-submitted the PR as #228.