https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108481
Bug ID: 108481
Summary: UBsan missed a signed integer overflow
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: shaohua.li at inf dot ethz.ch
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
For the following code, UBsan at -O1 and above missed the signed integer
overflow, while -O0 found it. I checked the assembly and the buggy code was not
optimized away.
Clang detected it at all optimization levels.
Compiler explorer: https://godbolt.org/z/rK6sad1WG
%cat a.c
int a, d;
short b;
short *c = &b;
int *const e = &d;
static char f(int *g, short h, long i) {
d = 2;
for (;; d--) {
int j = *e;
*g = (0 || h) / h;
*c = 3;
if ((i * (unsigned long)7 <= 1) << j)
;
else {
i = i - 6822162149299574294;
if (j) {
if (*g)
break;
continue;
}
return 8;
}
}
return h;
}
int main() {
int *k = &a;
f(k, 4, 8289379813243698614);
}
%
%gcc-tk -fsanitize=undefined -O1 && ./a.out
%
%gcc-tk -fsanitize=undefined -O0 && ./a.out
/a.c:14:9: runtime error: signed integer overflow: -5354944485355449974 -
6822162149299574294 cannot be represented in type 'long int'
%
