https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103552
Bug ID: 103552
Summary: Compile-time comparison of subobject and parent class
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
This program:
```
struct A{};
struct B : A { A a; };
int main() {
constexpr B b{};
static_assert( &static_cast<const A&>(b) < &b.a );
}
```
is accepted by GCC, but Clang rejects it with the error:
```
comparison of address of base class subobject 'A' of class 'B' to field 'a' has
unspecified value
```
Demo: https://gcc.godbolt.org/z/9G8szToPz
It looks like Clang is right here, and this indeed must be rejected.
