Antoine, I tested your commit with cc_r and it compiles fine (I have buildbot running now, just need to find a way to make the results publicly browsable).

I still think xlc_r would be a better choice as a default: at the moment ctypes will not compile on AIX, but cc_r will fail as soon as when it compiles _ctypes.c, while xlc_r will compile this file fine but fail later on libffi/src/powerpc/ffi.c

cc_r -qlanglvl=extc89 -DNDEBUG -O -O2 -O2 -Ibuild/temp.aix-6.1-3.2/libffi/include -Ibuild/temp.aix-6.1-3.2/libffi -I/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/libffi/src -I. -I./Include -I/home/cis/buildbot/support-buildbot/include -I/home/cis/buildbot/support-buildbot/include/ncurses -I/usr/local/include -IInclude -I/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build -c /san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c -o build/temp.aix-6.1-3.2/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.o
"build/temp.aix-6.1-3.2/libffi/include/ffi.h", line 133.27: 1506-207 (W) Integer constant 9223372036854775807 out of range.
"build/temp.aix-6.1-3.2/libffi/include/ffi.h", line 134.3: 1506-205 (S) #error "no 64-bit data type supported"
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 3222.27: 1506-068 (W) Operation between types "void*" and "int(*)(void)" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 3766.31: 1506-280 (W) Function argument assignment between types "int(*)(void)" and "void*" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 5386.63: 1506-280 (W) Function argument assignment between types "void*" and "void*(*)(void*,const void*,unsigned long)" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 5387.62: 1506-280 (W) Function argument assignment between types "void*" and "void*(*)(void*,int,unsigned long)" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 5388.65: 1506-280 (W) Function argument assignment between types "void*" and "struct _object*(*)(const char*,int)" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 5389.60: 1506-280 (W) Function argument assignment between types "void*" and "struct _object*(*)(void*,struct _object*,struct _object*)" is not allowed.
"/san_cis/home/cis/buildbot/buildbot-aix6/py3k/build/Modules/_ctypes/_ctypes.c", line 5391.66: 1506-280 (W) Function argument assignment between types "void*" and "struct _object*(*)(const unsigned short*,int)" is not allowed.