https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114537
--- Comment #1 from Fedor Chelnokov <fchelnokov at gmail dot com> ---
Probably related:
```
#include <bit>
struct A { int a: 7; };
static_assert( 1 == std::bit_cast<A>(std::bit_cast<int>(A{1})).a );
```
It looks valid and accepted by MSVC, but GCC prints:
error: '__builtin_bit_cast' accessing uninitialized byte at offset 0
Online demo: https://gcc.godbolt.org/z/3W5onY955
