A 64-bit build under Windows produces many compilation warnings, mostly related to lossy conversions between different int sizes.
Some of these warnings appear harmless after analysis (are MS 64 bit compilers pickier than their 32 bit counterparts?).
It would probably be spammy to open a separate issue per file.

5>..\Python\pythonrun.c(1210) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data

5>..\Python\Python-ast.c(3403) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3409) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3439) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3445) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3498) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3504) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3608) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3614) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3633) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3639) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3699) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3705) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3724) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3730) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3771) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3777) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3796) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3802) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3855) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3861) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3892) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(3898) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4016) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4022) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4041) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4047) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4092) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4098) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4117) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4123) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4167) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4173) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4192) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4198) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4253) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4259) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4326) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4332) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4351) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4357) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4376) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4382) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4414) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4420) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4439) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4445) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4510) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4516) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4559) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4565) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4607) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4613) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4643) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4649) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4791) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4797) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(4998) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5004) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5023) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5029) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5059) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5065) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5108) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5114) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5157) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5163) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5219) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5225) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5269) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5275) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5341) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5347) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5366) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5372) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5419) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5425) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5444) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5450) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5753) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5759) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5802) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5808) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5979) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(5985) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6356) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6362) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6456) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6462) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6508) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6514) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6555) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6561) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6602) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6608) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6627) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\Python-ast.c(6633) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Python\dtoa.c(1529) : warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data
5>..\Python\dtoa.c(1539) : warning C4244: '-=' : conversion from '__int64' to 'int', possible loss of data
5>..\Python\dtoa.c(1545) : warning C4244: '+=' : conversion from '__int64' to 'int', possible loss of data

5>..\Python\pystrtod.c(902) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\pystrtod.c(1023) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Python\peephole.c(84) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(184) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(237) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(309) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(352) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(403) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(418) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(459) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(544) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(555) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(587) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(601) : warning C4244: '-=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(632) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\peephole.c(661) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data
5>..\Python\peephole.c(671) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data

5>..\Python\getargs.c(390) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(502) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(876) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(931) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(939) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(983) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(1133) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(1476) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\getargs.c(1477) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>z:\py3k\__svn__\python\../Objects/stringlib/formatter.h(984) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\python\../Objects/stringlib/formatter.h(1161) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\python\../Objects/stringlib/formatter.h(1165) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Python\compile.c(339) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Python\compile.c(384) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Python\compile.c(479) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(533) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(947) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Python\compile.c(962) : warning C4244: 'return' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(1254) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(1399) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3678) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3704) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3730) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3898) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3902) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3942) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\compile.c(3949) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Python\ceval.c(3967) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Python\ceval.c(4155) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\PC\winreg.c(769) : warning C4267: '=' : conversion from 'size_t' to 'DWORD', possible loss of data
5>..\PC\winreg.c(801) : warning C4267: '+=' : conversion from 'size_t' to 'DWORD', possible loss of data
5>..\PC\winreg.c(851) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'DWORD', possible loss of data
5>..\PC\winreg.c(1186) : warning C4133: '=' : incompatible types - from 'wchar_t *' to 'BYTE *'

5>..\PC\_subprocess.c(345) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\PC\_subprocess.c(368) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\PC\_subprocess.c(369) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\PC\_subprocess.c(371) : warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data
5>..\PC\_subprocess.c(373) : warning C4244: 'initializing' : conversion from '__int64' to 'int', possible loss of data

5>..\Parser\tokenizer.c(658) : warning C4267: 'initializing' : conversion from 'size_t' to 'int', possible loss of data
5>..\Parser\tokenizer.c(689) : warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data

5>..\Parser\parsetok.c(199) : warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data

5>..\Parser\grammar.c(66) : warning C4244: 'return' : conversion from '__int64' to 'int', possible loss of data
5>..\Parser\grammar.c(108) : warning C4244: 'return' : conversion from '__int64' to 'int', possible loss of data

5>..\Objects\typeobject.c(6173) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Objects\setobject.c(743) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Objects\setobject.c(772) : warning C4244: '*=' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Objects\setobject.c(819) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'long', possible loss of data

5>..\Objects\obmalloc.c(904) : warning C4244: '=' : conversion from '__int64' to 'unsigned int', possible loss of data

5>..\Objects\funcobject.c(633) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\funcobject.c(634) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\funcobject.c(634) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Objects\frameobject.c(480) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\frameobject.c(513) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\frameobject.c(871) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\frameobject.c(872) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\frameobject.c(918) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\frameobject.c(919) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Objects\fileobject.c(401) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned int', possible loss of data

5>..\Objects\descrobject.c(891) : warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data

5>..\Objects\codeobject.c(495) : warning C4244: 'initializing' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\codeobject.c(517) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Objects\bytesobject.c(786) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\bytesobject.c(795) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\bytesobject.c(1755) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\bytesobject.c(1947) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\bytesobject.c(2620) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data
5>..\Objects\bytesobject.c(2641) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data
5>..\Objects\bytesobject.c(2696) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data

5>..\Objects\bytearrayobject.c(1222) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Objects\bytearrayobject.c(1231) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Objects\bytes_methods.c(454) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data

5>..\Modules\_io\fileio.c(483) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned int', possible loss of data
5>..\Modules\_io\fileio.c(566) : warning C4267: 'function' : conversion from 'size_t' to 'unsigned int', possible loss of data
5>..\Modules\_io\fileio.c(622) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned int', possible loss of data
5>..\Modules\_io\fileio.c(662) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned int', possible loss of data

5>..\Modules\zlibmodule.c(127) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\zlibmodule.c(211) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\zlibmodule.c(217) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(271) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(422) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\zlibmodule.c(434) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(451) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(505) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\zlibmodule.c(526) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(556) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(935) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(938) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(963) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data
5>..\Modules\zlibmodule.c(966) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'uInt', possible loss of data

5>..\Modules\sha512module.c(558) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\sha512module.c(710) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\sha512module.c(751) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Modules\sha256module.c(492) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\sha256module.c(644) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\sha256module.c(685) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Modules\sha1module.c(399) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned long', possible loss of data
5>..\Modules\sha1module.c(520) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned long', possible loss of data

5>..\Modules\posixmodule.c(394) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
5>..\Modules\posixmodule.c(3708) : warning C4133: 'function' : incompatible types - from 'int *' to 'Py_ssize_t *'
5>..\Modules\posixmodule.c(4886) : warning C4244: 'function' : conversion from 'Py_intptr_t' to 'long', possible loss of data
5>..\Modules\posixmodule.c(5593) : warning C4267: 'function' : conversion from 'size_t' to 'unsigned int', possible loss of data

5>..\Modules\mmapmodule.c(881) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data

5>..\Modules\md5module.c(423) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned long', possible loss of data
5>..\Modules\md5module.c(544) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'unsigned long', possible loss of data

5>..\Modules\binascii.c(667) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'unsigned char', possible loss of data

5>..\Modules\audioop.c(332) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(354) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(376) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(398) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(423) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(632) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(687) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(737) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(763) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(810) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(868) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(928) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(984) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1018) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1053) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1284) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1316) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1353) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1385) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1424) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\audioop.c(1530) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>z:\py3k\__svn__\modules\_sre.c(1898) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(1901) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(1935) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(1938) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2082) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2085) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2212) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2215) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2364) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(2367) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(3753) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(3756) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(3786) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>z:\py3k\__svn__\modules\_sre.c(3789) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Modules\_pickle.c(284) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(301) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(461) : warning C4244: '+=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(628) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'long', possible loss of data
5>..\Modules\_pickle.c(647) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(1320) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(1558) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_pickle.c(1806) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Modules\_csv.c(971) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_csv.c(1100) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_csv.c(1105) : warning C4244: 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
5>..\Modules\_csv.c(1133) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

5>..\Modules\_collectionsmodule.c(1124) : warning C4244: 'function' : 
conversion from 'Py_ssize_t' to 'long', possible loss of data

This must be a duplicate report - this issue has been known for years, and Kristjan and others (including myself) volunteered to work on it, and did actually work on it.

I don't think it's necessary to have a bug report in the bug tracker for it. If you find a place that you would like to fix, just go ahead and fix it.

Please keep in mind the following principles:
- if a value can reasonably overflow an int, change the data type to something larger (typically Py_ssize_t)
- if the value can overflow in principle, but likely won't, and  it is difficult to fix the data type (e.g. because it's at a system interface), make a range check, raise a Python exception, and then SAFECAST the value.
- if the value "shouldn't" overflow (i.e. you are believe from the data flow or other invariants that it can't happen), use a safecast
- if you are certain that the value can't overflow (e.g. if you are converting the result of a sizeof of some structure), use a regular cast, along with a comment

This leaves us with a number of cases where there are pragmatic Python limitations (such as the data type for line numbers, or the number of values when building a tuple in source) which make it impossible to get overflows in the current implementation. Such limitations should be collected in some place, and then SAFECASTs should be added, along with asserts at startup (e.g. that a certain datatype has no more than 2 bytes).

Created #9611 to report the FileIO 64-bit issue under Windows.

Created #9612 for the mostly harmless warnings in the set implementation.

The zlib warnings are genuine and there's a specific bug for 64-bitness of zlibmodule.c: #8650.

Opened #9613 for 64-bitness of process ids.

Opened #9614 for the _pickle issues (which look quite legitimate).

r87733 fixes some conversions in:

 * Python/pythonrun.c
 * Objects/codeobject.c
 * Objects/typeobject.c
 * Objects/listobject.c
 * Modules/_ctypes/_ctypes.c
 * Modules/sha512module.c
 * Modules/unicodedata.c
 * Modules/selectmodule.c
 * Modules/pyexpat.c
 * Modules/audioop.c
 * Modules/sha1module.c
 * Modules/sha256module.c
 * Modules/_testcapimodule.c
 * Modules/md5module.c

For md5, sha1, sha256 and sha512: a smaller type (int) can be used for the local n variable. I don't know if it impacts performances or not. md5 and sha1 used "unsigned long", sha256 and sha512 used "int".

r87733 in pyexpat.c modified a call to PyErr_Format with a %zi format code.
This format does not seem to be supported. %zd should be used instead.

#10823 has been marked as a duplicate of this issue.

haypo: please avoid introducing explicit casts (such as the one in pyexpat.c). Use SAFECASTs instead. If you are absolutely certain that a cast cannot possibly truncate, add a comment explaining why that is. In the specific case, I think it actually *is* possible that the cast truncates, because the case that read() returned too many bytes is incorrectly handled (it should set len to -1).

amaury> r87733 in pyexpat.c modified a call to PyErr_Format with a %zi
amaury> format code. This format does not seem to be supported. %zd
amaury> should be used instead.

Oh, that's surprising. Why %zd is supported but not %zi?

PyUnicode_FromFormatV() supports %d, %ld, %lld, %zd, %i, but not %li, %lli or %zi. Before fixing PyUnicode_FromFormatV(), I fixed pyexpat.c: r87747.

MvL> If you are absolutely certain that a cast cannot possibly truncate, 
MvL> add a comment explaining why that is.

Ah yes, sorry, I forgot to add a comment: done in r87746.

> Python\pystrtod.c(902) : 'function' : conversion from 'Py_ssize_t' to 'int', possible loss of data
> Python\pystrtod.c(1023) : '=' : conversion from 'Py_ssize_t' to 'int', possible loss of data

I asked dmalcolm on IRC if int or Py_ssize_t should be used:

"this is the number of digits to use in the floating point representation, right? it strikes me that if you're overflowing an int, you're asking for a very very very long string" (yes, INT_MAX is usually 2^31)

"... looking at usage of precision seems to ultimately land in Python/dtoa.c, which uses int..."

> MvL> If you are absolutely certain that a cast cannot possibly truncate, 
> MvL> add a comment explaining why that is.
> 
> Ah yes, sorry, I forgot to add a comment: done in r87746.

But the comment is actually wrong: It says

len <= buf_size <= INT_MAX (see above)

however, len > buf_size may happen, after this code:

    if (len > buf_size) {
        PyErr_Format(PyExc_ValueError,
                     "read() returned too much data: "
                     "%i bytes requested, %zd returned",
                     buf_size, len);
        goto finally;
    }

> But the comment is actually wrong: It says
> 
> len <= buf_size <= INT_MAX (see above)
> 
> however, len > buf_size may happen, after this code:
> 
>     if (len > buf_size) {
>         PyErr_Format(PyExc_ValueError,
>                      "read() returned too much data: "
>                      "%i bytes requested, %zd returned",
>                      buf_size, len);
>         goto finally;
>     }

Oh. Not only is the comment is wrong, but the code is also wrong. It
should return a negative value on error, whereas it returns the string
length which is always positive (except on a unlikely Py_ssize_t => int
overflow?).

> Oh. Not only is the comment is wrong, but the code is also wrong. It
> should return a negative value on error, whereas it returns the string
> length which is always positive (except on a unlikely Py_ssize_t => int
> overflow?).

Right. See msg125367.

pyexpat.patch: new try, does it look better?

> [readinst) should return a negative value on error, whereas it 
> returns the string length which is always positive

Fixed by r87911.

socketmodule_int.patch: Fix similar to the fix for #9611: clamp length to INT_MAX on Windows for recv(), recvfrom(), send() and sendto().

ssl_sock_fd_int.patch: add SOCKET_T_AS_INT(fd) macro to cast a socket descriptor (SOCKET_T) to int. I choosed a macro just to not have to repeat a comment twice :-)

It looks like it is a safe to cast SOCKET_T to int. My comment:

/* On Windows, SOCKET_T is an offset in per-process handle table.
   The per-process limit on kernel handles is 2^24. Kernel Objects:
   http://msdn.microsoft.com/en-us/library/ms724485%28VS.85%29.aspx
*/

> On Windows, SOCKET_T is an offset in per-process handle table.
> The per-process limit on kernel handles is 2^24. Kernel Objects:

Reference: http://www.mail-archive.com/openssl-dev@openssl.org/msg23781.html

ssl_write.patch: always clamp SSL_Write() size to INT_MAX. This patch fixes also an overflow if Py_ssize_t is 32 bits (if the size is bigger than INT_MAX).

hash.patch: continue my fix on md5, sha1, sha256, sha512.

_sre.patch: store sre_match() result in Py_ssize_t instead of int.

... and issue9566.patch: various fixes. Interesting parts:

---
-    id = PyLong_FromLong((Py_uintptr_t) self);
+    id = PyLong_FromVoidPtr(self);
---

---
 LOCAL(PyObject*)
-expat_parse(XMLParserObject* self, char* data, int data_len, int final)
+expat_parse(XMLParserObject* self, char* data, Py_ssize_t data_len, int final)
 {
     int ok;
 
-    ok = EXPAT(Parse)(self->parser, data, data_len, final);
+    if (data_len > INT_MAX) {
+        PyErr_SetString(PyExc_OverflowError, "length doesn't fit in an int");
+        return NULL;
+    }
+
+    ok = EXPAT(Parse)(self->parser, data, (int)data_len, final);
---

---
-        long hash = PyObject_Hash(arg);
+        Py_hash_t hash = PyObject_Hash(arg);
---

New changeset 43fd627cc060 by Victor Stinner in branch 'default':
Issue #9566: cast unsigned int to Py_ssize_t in md5 and sha1 modules
http://hg.python.org/cpython/rev/43fd627cc060