https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102013

            Bug ID: 102013
           Summary: Incorrect aggregate initialization of union
           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: ---

In this program:
```
#include <iostream>

struct A { int x = 1; };
struct B { int x = 0; };

union U {
    A a;
    B b;
};

int main() {
    U u{};
    std::cout << u.a.x;
}
```

GCC prints `0`: https://gcc.godbolt.org/z/8Tj4Y1Pv1
But the correct result is `1`, which is the default initializer of the first
union member `a` (see Clang 's result)

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