cast long into pointer

Question

Can this cast fail and when?

long x=-1;
long y = (long)(void*)x;
assert(x==y);

More specifically, how to detect if the above cast is OK at compile time.

Answer 1

A more portable way (on the C99 standard variant) is to #include <stdint.h> and then cast pointers to intptr_t (and back). This integer type is guaranteed to be the size of a pointer.