https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117341
Bug ID: 117341
Summary: GCC 13.2.0 and 14.2.0 generate wrong code with -O3
Product: gcc
Version: 14.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: newsigma at 163 dot com
Target Milestone: ---
Hi,
It seems GCC 13.2.0 and 14.2.0 generate wrong code in my case, while GCC 9.5.0
works fine.
GCC version: 13.2.0 and 14.2.0 have this bug, while 9.5.0 not
System: Ubuntu 24.04
GCC Build Option: Use gcc installed from apt. Detailed options are lengthy
Here is a minimal reproducer, simply copy them into a main.cpp.
Build command: gcc main.cpp -O3 -o main
```
#include <iostream>
#include <vector>
class Array {
double arr[1];
public:
Array() = default;
Array(const Array&) = default;
Array(Array&&) noexcept = default;
~Array() = default;
/* Operators */
[[nodiscard]] double& operator[](int index) { return arr[index]; }
[[nodiscard]] const double& operator[](int index) const { return
arr[index]; }
/* Operations */
void swap(Array& __restrict array) noexcept {
for (int i = 0; i < 1; ++i)
std::swap(arr[i], array[i]);
}
};
class Vector : public Array {};
int main() {
std::vector<Vector> solution;
solution.resize(4);
solution[0][0] = 1;
auto func = [](const Vector& y) -> Vector { return y; };
for (int i = 0; i < 3; ++i) {
const Vector& v = solution[i];
Vector sum{};
const double delta = func(v)[0] * 0;
sum[0] = v[0] + delta;
solution[i + 1].swap(sum);
}
for (auto e : solution)
std::cout << e[0] << ' ';
std::cout << std::endl;
return 0;
}
```
Expected output(GCC 9.5.0): 1, 1, 1, 1
Wrong output(GCC 13.2.0 and 14.2.0): 1, 1, 0, 0
If I was wrong, please inform me. Thanks you.
