I don’t know anything about AIX specific stuff, but I left some general comments in the code review.

Is there any chance that AIX people would be relying on the current behaviour that I understand uses _findSoname_ldconfig() and _findLib_gcc()?

Is this new functionality covered by the test suite? E.g. in /Lib/ctypes/test/test_find.py, there are tests that call find_library() for GL, GLU, and gle. Are those libraries common on AIX?

As discussed in Issue 9998, it seems a lot of people use find_library() to help convert a build-time library name to a run-time shared library name that can be passed to CDLL() or LoadLibrary(). E.g. on Linux:

>>> find_library("python2.7")  # As used in cc . . . -lpython2.7
'libpython2.7.so.1.0'
>>> cdll.LoadLibrary("libpython2.7.so.1.0")
<CDLL 'libpython2.7.so.1.0', handle 7f58e7495000 at 7f58e573ac90>

Does your patch support this kind of use case?