https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117679
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
```
struct A {
char u, v, w;
};
struct X { char x; };
struct B : X {
A y;
};
constexpr A f() {
union U {
A a{ 1, 2, 3 };
B b;
} u;
u.b.y = u.a; // when does the life time of u.b start, during the statement?
return u.b.y;
}
// ok in GCC and MSVC, fails in Clang
static_assert( f().w == 3 );
int main() {
return f().w; //2 in GCC with -O0
}
```
So I think this is similar as the above. This produces similar results as GCC,
clang, and MSVC for the original testcase.
EDG also accepts this code and produces 3 for main.
Note I think only GCC -O0 code generation is wrong for main.
basic.life/1 says:
```
The lifetime of an object o of type T ends when:
...
the storage which the object occupies is released, or is reused by an object
that is not nested within o (6.7.2 [intro.object]).
```
But it is not obvious.
