PY_SSIZE_T_MAX is currently defined in Include/pyport.h as: 

#define PY_SSIZE_T_MAX ((Py_ssize_t)(((size_t)-1)>>1))

This is not an integer constant expression, which means it can't be used in preprocessor conditionals.  For example: 

#if PY_SSIZE_T_MAX > UINT32_MAX

will fail to compile.  This was touched upon and ignored a long time ago: 

https://mail.python.org/archives/list/python-dev@python.org/thread/27X7LINL4UO7DAJE6J3IFQEZGUKAO4VL/

I think the best fix is to move the definition of PY_SSIZE_T_MAX (and PY_SSIZE_T_MIN) next to the definition of Py_ssize_t, and use the proper corresponding limit macro.  If Py_ssize_t is a typedef for ssize_t, then PY_SSIZE_T_MAX should be SSIZE_MAX.  If Py_ssize_t is a typedef for Py_intptr_t, then PY_SSIZE_T_MAX should be INTPTR_MAX.  There's a minor complication because Py_ssize_t can be defined in PC/pyconfig.h.  I'm not so familiar with the various Windows compilers, so I'm not sure what's best to do here.  I think __int64 has a corresponding _I64_MAX macro, and int obviously has INT_MAX.