https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68998
Bug ID: 68998
Summary: Wrong code generated regarding constexpr arrays
Product: gcc
Version: 5.3.1
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: likan_999.student at sina dot com
Target Milestone: ---
The following code generates wrong result:
#include <iostream>
using namespace std;
template <typename T, int N> struct ArrayHolder { T v[N]; };
constexpr ArrayHolder<int, 2> makeArray() {
ArrayHolder<int, 2> a{};
a.v[1] = 1;
a.v[0] = 1;
return a;
}
constexpr ArrayHolder<int, 2> arr = makeArray();
int main() {
cout << arr.v[0] << endl;
for (int i = 0; i < 2; i++) {
for (int j = 0; j < arr.v[i]; j++) {
cout << "i = " << i << ", j = " << j << endl;
}
}
}
Result:
[hidden] g++ -std=c++14 c.cpp && ./a.out
1
i = 1, j = 0
Expected Result:
1
i = 0, j = 0
i = 1, j = 0
I am using priority 'critical' because it generates wrong code, silently, so it
is very bad.
