https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117426
Bug ID: 117426
Summary: Miscompile with different optimization flags
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: yunboni at smail dot nju.edu.cn
Target Milestone: ---
When I compiled this code with -O0/1/2, its output is 1. While with -O3, its
output is 0:
```c
int printf(const char *, ...);
int a[6];
int b, d, i, j, l, m, n;
char *c;
int f[8][8][4];
int *g = &d;
char p[11];
int main() {
short q[6];
int k = 0;
for (; k < 2; k++) {
{
char o[3];
int e = 53;
char *h = o;
c = p;
while (e)
*c++ = e /= 10;
while (c != p)
*h++ = *--c;
*h++ = '\0';
n = h - o;
}
q[n - 2] = 1;
}
*g = q[1];
printf("%d\n", d);
l = 0;
for (; l < 10; l++)
if (m)
printf("index = \n");
i = 0;
for (; i < 7; i++) {
j = 0;
for (; j < 7; j++)
b = a[b];
}
j = 0;
for (; j < 8; j++) {
l = 0;
for (; l < 4; l++)
b = a[b ^ f[i][j][l]];
}
}
```
This bug can be reproduced by 14.1 and later versions. I've checked the code
with -Wall and -Wextra.
The details can be found here: https://godbolt.org/z/1a9EbfoP6
