Here's a patch that fixes this by making both Python's malloc and
realloc return NULL if (0 <= size <= PY_SSIZE_T_MAX).

A side effect of this is that strings on 32bit platforms can no longer
be allocated up to 2**31-1 in length as the malloc includes the internal
python object structure overhead.  The maximum string size becomes
2147483609 with an optimized build on this system.

I do not think that is a problem.  A 32-bit process by definition can
only ever have one such object allocated at a time anyways. ;)

any objections?