https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127964
Bug ID: 127964
Summary: Wrong code at -O2 with infinite recursive jump and
hang
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: ---
#include <stdio.h>
#include <stdint.h>
__attribute__((noinline))
static uint32_t crc32_bytes(uint32_t crc, const unsigned char *p, unsigned n)
{
for (unsigned k = 0; k < n; k++) {
crc ^= p[k];
unsigned j = 0;
for (;;) {
if (crc & 1)
crc = (crc >> 1) ^ 0xEDB88320u;
else
crc = crc >> 1;
j++;
if (j == 8)
break;
}
}
return crc;
}
int main(void)
{
const unsigned char msg[] = "123456789";
uint32_t c = crc32_bytes(0xFFFFFFFFu, msg, 9);
printf("%08x\n", c ^ 0xFFFFFFFFu);
return 0;
}
godbolt: https://gcc.godbolt.org/z/x5WvT8eE3
With -O2, the executable hangs due to a jump to itself; it did not happen on
-O{0,1,3}.
O2 assembly:
"crc32_bytes.constprop.0":
.L2:
jmp .L2
"main":
sub rsp, 16
lea rdi, [rsp+6]
call "crc32_bytes.constprop.0"
