Continuation of bpo 39825, this time for FreeBSD and AIX. As commented there, the test added in the fix to 39825 fails on FreeBSD and AIX:

FAIL: test_EXT_SUFFIX_in_vars (test.test_sysconfig.TestSysConfig)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-564d/build/Lib/test/test_sysconfig.py", line 368, in test_EXT_SUFFIX_in_vars
    self.assertEqual(vars['EXT_SUFFIX'], _imp.extension_suffixes()[0])
AssertionError: '.so' != '.cpython-310d.so'
- .so
+ .cpython-310d.so

So somehow EXT_SUFFIX is being set to .so rather than .cpython-310d.so.

It seems the difference in EXT_SUFFIX comes from this stanza in configure:

case $ac_sys_system in
    Linux*|GNU*|Darwin|VxWorks)
	EXT_SUFFIX=.${SOABI}${SHLIB_SUFFIX};;
    *)
	EXT_SUFFIX=${SHLIB_SUFFIX};;
esac

where $ac_sys_system is `uname -s`. On FREEBSD, this is "FreeBSD", and I think on AIX it is "AIX". My preference would be to always set EXT_SUFFIX to ${SOABI}${SHLIB_SUFFIX}, with no option for setting it to a different value. Does that seem right?