MSVC is not happy, here's some build output:

"P:\ath\to\cpython\PCbuild\pcbuild.sln" (Build target) (1) ->
"P:\ath\to\cpython\PCbuild\python.vcxproj" (default target) (2) ->
"P:\ath\to\cpython\PCbuild\pythoncore.vcxproj" (default target) (3) ->
(ClCompile target) ->
  ..\Modules\posixmodule.c(2886): warning C4047: 'initializing' : 'int' differs in levels of indirection from 'void *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(2896): warning C4047: 'return' : 'int' differs in levels of indirection from 'void *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(2900): warning C4047: 'return' : 'int' differs in levels of indirection from 'void *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4865): warning C4047: '=' : 'int' differs in levels of indirection from 'Py_UNICODE *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4866): warning C4047: '==' : 'int' differs in levels of indirection from 'void *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4877): warning C4047: 'function' : 'LPCWSTR' differs in levels of indirection from 'int' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4877): warning C4024: 'CreateFileW' : different types for formal and actual parameter 1 [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(5368): warning C4047: 'function' : 'path_t *' differs in levels of indirection from 'path_t **' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(5368): warning C4024: 'path_error2' : different types for formal and actual parameter 1 [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(5368): warning C4047: 'function' : 'path_t *' differs in levels of indirection from 'path_t **' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(5368): warning C4024: 'path_error2' : different types for formal and actual parameter 2 [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(7010): warning C4031: second formal parameter list longer than the first list [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(9894): warning C4013: 'waitpid' undefined; assuming extern returning int [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(10428): warning C4047: 'function' : 'path_t *' differs in levels of indirection from 'path_t **' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(10428): warning C4024: 'path_error2' : different types for formal and actual parameter 1 [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(10428): warning C4047: 'function' : 'path_t *' differs in levels of indirection from 'path_t **' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(10428): warning C4024: 'path_error2' : different types for formal and actual parameter 2 [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(16433): warning C4047: 'return' : 'int' differs in levels of indirection from 'void *' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]


"P:\ath\to\cpython\PCbuild\pcbuild.sln" (Build target) (1) ->
"P:\ath\to\cpython\PCbuild\python.vcxproj" (default target) (2) ->
"P:\ath\to\cpython\PCbuild\pythoncore.vcxproj" (default target) (3) ->
(ClCompile target) ->
  ..\Modules\posixmodule.c(3324): error C2231: '.wide' : left operand points to 'struct', use '->' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4863): error C2082: redefinition of formal parameter 'path' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4865): error C2065: 'path_wchar' : undeclared identifier [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4866): error C2065: 'path_wchar' : undeclared identifier [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(4877): error C2065: 'path_wchar' : undeclared identifier [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(7004): error C2370: 'os_spawnv__doc__' : redefinition; different storage class [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(7014): error C2084: function 'PyObject *os_spawnv(PyModuleDef *,PyObject *)' already has a body [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(7037): error C2084: function 'PyObject *os_spawnv_impl(PyModuleDef *,int,PyObject *,PyObject *,PyObject *)' already has a body [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(9019): error C2082: redefinition of formal parameter 'pid' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(10936): error C2231: '.wide' : left operand points to 'struct', use '->' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(13997): error C2085: 'win32__getdiskusage' : not informal parameter list [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(13997): error C2143: syntax error : missing ';' before '{' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(16483): error C2085: 'posix_set_handle_inheritable' : not in formal parameter list [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(16483): error C2143: syntax error : missing ';' before '{' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17051): error C2065: 'OS_SPAWNVE_METHODDEF' : undeclared identifier [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17051): error C2099: initializer is not a constant [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17051): error C2059: syntax error : '{' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17051): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17053): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17055): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17056): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17060): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17078): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17084): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17085): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17086): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17087): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17088): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17089): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17091): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17092): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17095): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17102): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17103): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17104): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17115): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17117): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17119): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17136): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17138): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17139): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17141): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17142): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17143): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17145): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17157): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17159): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17160): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17161): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17162): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17163): error C2059: syntax error : ',' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17165): error C2059: syntax error : '}' [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]
  ..\Modules\posixmodule.c(17175): fatal error C1903: unable to recover from previous error(s); stopping compilation [P:\ath\to\cpython\PCbuild\pythoncore.vcxproj]

    18 Warning(s)
    53 Error(s)