https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127497
Bug ID: 127497
Summary: Wrong code with -fwrapv-pointer at -O1/2
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kyuwoncho18 at gmail dot com
Target Milestone: ---
fwrapv-pointer allows pointer overflow as defined behavior, but the
optimization generates wrong code when it does.
Reproducer:
#include <stdio.h>
#pragma GCC optimize ("wrapv-pointer") // or -fwrapv-pointer
__attribute__((noinline)) unsigned long
f (char *p, unsigned long len)
{
char *q = p + len;
unsigned long n = 0;
do
{
n++;
p += 4;
}
while (p < q);
return n;
}
int
main (void)
{
printf ("%lu\n", f ((char *) (__UINTPTR_TYPE__) -3, 8));
return 0;
}
Output:
O0/3/g: 2
O1/2/s/z: 1
