https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108377
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So we have:
const __SIZE_TYPE__ n = calc_n(259);
#if 1
haystack = __builtin_malloc(n + 1);
if (!haystack)
__builtin_abort();
for (__SIZE_TYPE__ i = 0; i < n + 1; ++i)
haystack[i] = '0';
#endif
needle = __builtin_malloc(n);
If calc_n(259) returns (__SIZE_TYPE__)-1 (aka 18446744073709551615). n+1 would
be 0 which will is fine for malloc. and then the for is skipped if n+1 == 0 and
a jump threading happens so you get two copies of the second malloc and then
you get a malloc which has 18446744073709551615.
So the warning is correct (and code produced) in some sense of correctness.
Maybe the best thing is add an assume after the call to calc_n that it will be
small or smaller than the n or so.
