With gcc 4.2.3, I see a whole bunch of warnings:

Objects/exceptions.c: In function ‘UnicodeDecodeError_init’:
Objects/exceptions.c:1472: warning: dereferencing type-punned pointer
will break strict-aliasing rules

Objects/frameobject.c: In function ‘frame_setlineno’:
Objects/frameobject.c:151: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicode_DecodeUTF7Stateful’:
Objects/unicodeobject.c:1804: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:1815: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:1827: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeUTF8Stateful’:
Objects/unicodeobject.c:2140: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2147: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeUTF32Stateful’:
Objects/unicodeobject.c:2419: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2419: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2420: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2431: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeUTF16Stateful’:
Objects/unicodeobject.c:2693: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2693: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2694: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2705: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeUnicodeEscape’:
Objects/unicodeobject.c:2911: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2923: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:2962: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3004: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3018: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3030: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeRawUnicodeEscape’:
Objects/unicodeobject.c:3295: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3327: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3333: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘_PyUnicode_DecodeUnicodeInternal’:
Objects/unicodeobject.c:3502: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3512: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeASCII’:
Objects/unicodeobject.c:3875: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:3880: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_DecodeCharmap’:
Objects/unicodeobject.c:4176: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:4226: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:4249: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:4276: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_Join’:
Objects/unicodeobject.c:5724: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:5745: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c: In function ‘PyUnicodeUCS2_Format’:
Objects/unicodeobject.c:8841: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:9158: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Objects/unicodeobject.c:9223: warning: dereferencing type-punned pointer
will break strict-aliasing rules
Python/bltinmodule.c: In function ‘source_as_string’:
Python/bltinmodule.c:513: warning: dereferencing type-punned pointer
will break strict-aliasing rules
./Modules/_codecsmodule.c: In function ‘unicode_internal_decode’:
./Modules/_codecsmodule.c:243: warning: dereferencing type-punned
pointer will break strict-aliasing rules
./Modules/_codecsmodule.c: In function ‘unicode_internal_encode’:
./Modules/_codecsmodule.c:700: warning: dereferencing type-punned
pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/_struct.c: In function ‘s_pack_into’:
/home/alex/src/python.org/py3k/Modules/_struct.c:1782: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/audioop.c: In function
‘audioop_findfit’:
/home/alex/src/python.org/py3k/Modules/audioop.c:480: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/audioop.c:480: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/audioop.c: In function
‘audioop_findfactor’:
/home/alex/src/python.org/py3k/Modules/audioop.c:537: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/audioop.c:537: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/audioop.c: In function
‘audioop_findmax’:
/home/alex/src/python.org/py3k/Modules/audioop.c:570: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/nismodule.c: In function
‘nis_xdr_ypmaplist’:
/home/alex/src/python.org/py3k/Modules/nismodule.c:293: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/nismodule.c: In function
‘nis_xdr_ypresp_maplist’:
/home/alex/src/python.org/py3k/Modules/nismodule.c:319: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/_cursesmodule.c: In function
‘PyCurses_UngetMouse’:
/home/alex/src/python.org/py3k/Modules/_cursesmodule.c:1846: warning:
dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_hk.c: In
function ‘big5hkscs_codec_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_hk.c:23:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_hk.c:23:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c: In
function ‘ksx1001_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:573:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:574:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c: In
function ‘jisx0208_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:609:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:610:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c: In
function ‘jisx0212_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:650:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:651:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c: In
function ‘jisx0213_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:688:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:690:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:692:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:694:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:696:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:698:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:700:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:700:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c: In
function ‘gb2312_init’:
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:957:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/alex/src/python.org/py3k/Modules/cjkcodecs/_codecs_iso2022.c:958:
warning: dereferencing type-punned pointer will break strict-aliasing rules