I'm using an IBM compiler running in AIX 5.3.
Compilation of Python 2.6 fails (see explanation below).
Compilation of Python 2.5.2 is ok.

/home/xyz/python/Python-2.6$ lslpp -L | grep vac
  vac.C                     10.1.0.0    C     F    IBM XL C Compiler
  vac.aix53.lib             10.1.0.0    C     F    XL C for AIX
Libraries for AIX
  vac.include               10.1.0.0    C     F    IBM XL C Compiler Include
  vac.lib                   10.1.0.0    C     F    XL C for AIX Libraries
  vac.lic                   10.1.0.0    C     F    XL C for AIX Licence
Files
  vacpp.cmp.rte             10.1.0.0    C     F    IBM XL C/C++ Compiler
  vacpp.cmp.tools           10.1.0.0    C     F    IBM XL C/C++ Tools
  vacpp.licAgreement        10.1.0.0    C     F    IBM XL C++ Electronic
License
  vacpp.memdbg.aix53.rte    10.1.0.0    C     F    IBM XL C/C++ User
Heap/Memory
  vacpp.memdbg.rte          10.1.0.0    C     F    IBM XL C/C++ User
Heap and

Configure --prefix <some path> 
runs ok.
Then, make fails:

/home/xyz/python/Python-2.6$ make
        cc_r -qlanglvl=extc89 -c  -DNDEBUG -O  -I. -IInclude -I./Include
-I/usr/local/include/  -DPy_BUILD_CORE -o Objects/frameobject.o
Objects/frameobject.c
"Objects/frameobject.c", line 520.9: 1506-046 (S) Syntax error.
"Objects/frameobject.c", line 520.12: 1506-045 (S) Undeclared identifier
subtract.
make: The error code from the last command is 1.