Igor Bukanov <igor@xxxxxxxx> writes:
> is it possible to tell GCC that a pointer cannot be NULL at a
> particular point so the compiler can optimize the control flaw better
> and avoid redundant NULL checks on the fast paths?
As of gcc 4.5 you can do this using __builtin_unreachable.
In your example:
if (n != a->end) {
a->start += 16; /* size of the thing to allocate. */
if (n == 0)
__builtin_unreachable();
return n; /* n cannot be NULL here */
}
Use this with care. If you get it wrong, the results will be wholly
unpredictable.
Ian
