https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92695
Bug ID: 92695
Summary: [10, 9] P1064R0 - virtual constexpr fails if object
taken from array
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
The following code fails with:
-> error: expression 'A::get' is not a constant expression
Compiled with `-std=c++2a` under GCC-9.2 and GCC-trunk. It works under
Clang-trunk.
```
struct A {
constexpr virtual int get() = 0;
};
struct B : A {
constexpr int get() override {
return 10;
}
};
struct Foo {
B b[1] = {};
constexpr A * get_a() {
// Seems to be the problem.
return &(b[0]);
}
};
constexpr int get() {
Foo f;
return f.get_a()->get();
}
constexpr auto a = get();
int main() {
return a;
}
```
The dereferencing of the array seems to be the problem.
See online here: https://gcc.godbolt.org/z/ZSXAfb
