https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104789
Bug ID: 104789
Summary: [12 Regression] New -Wstringop-overflow false positive
since r12-5863-g9354a7d70caef1c9
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: marxin at gcc dot gnu.org
CC: msebor at gcc dot gnu.org
Target Milestone: ---
It's originally reported here:
https://github.com/godotengine/godot/issues/58747
$ cat godot-stringop.cpp
#include <cstdint>
#include <cstdio>
uint32_t some_func(const uint32_t components) {
uint8_t header[8];
uint32_t header_bytes = 0;
for (uint32_t i = 0; i < components; i++) {
header_bytes += 2;
}
header_bytes += 2;
// This works it around, but shouldn't be needed AFAICT.
//while (header_bytes != 8 && header_bytes % 4 != 0) {
while (header_bytes % 4 != 0) {
header[header_bytes++] = 0;
}
for (uint32_t i = 0; i < header_bytes; i++) {
printf("%d\n", header[i]);
}
return header_bytes;
}
int main() {
some_func(1);
some_func(3);
return 0;
}
$ g++ godot-stringop.cpp -c -Werror=all -O3
godot-stringop.cpp: In function ‘uint32_t some_func(uint32_t)’:
godot-stringop.cpp:14:40: error: writing 1 byte into a region of size 0
[-Werror=stringop-overflow=]
14 | header[header_bytes++] = 0;
| ~~~~~~~~~~~~~~~~~~~~~~~^~~
godot-stringop.cpp:5:17: note: at offset 8 into destination object ‘header’ of
size 8
5 | uint8_t header[8];
| ^~~~~~
cc1plus: some warnings being treated as errors
