summary of compiler errors/warnings i just hit in the same situation
with stock Python-2.6.tgz:

>>>>>>>>>>>>>> c++ style comment used
"Objects/frameobject.c", line 520.9: 1506-046 (S) Syntax error.
"Objects/unicodeobject.c", line 118.1: 1506-046 (S) Syntax error.
"Objects/unicodeobject.c", line 125.1: 1506-046 (S) Syntax error.
"Objects/unicodeobject.c", line 130.1: 1506-046 (S) Syntax error.
"Objects/unicodeobject.c", line 149.1: 1506-046 (S) Syntax error.
"Objects/unicodeobject.c", line 153.1: 1506-046 (S) Syntax error.
& a bunch of other places in unicodeobject.c
"Python/_warnings.c", line 380.19: 1506-046 (S) Syntax error.
"Python/_warnings.c", line 803.5: 1506-046 (S) Syntax error.

>>>>>>>>>>>>>> inline keyword was used
"./Modules/signalmodule.c", line 112.1: 1506-277 (S) Syntax error:
possible missing ';' or ','?

>>>>>>>>>>>>>> other warning
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for M is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for N is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for O is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for P is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for Q is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for R is not valid. Type unsigned assumed.
"/tmp/Python-2.6/Modules/_ctypes/_ctypes_test.c", line 373.9: 1506-159
(E) Bit field type specified for S is not valid. Type unsigned assumed.