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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/114537] bit_cast does not work NSDMI of bitfields
Date: Mon, 01 Apr 2024 13:54:21 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114537

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Fedor Chelnokov from comment #1)
> Probably related:
> ```
> #include <bit>
>=20
> struct A { int a: 7; };
>=20
> static_assert( 1 =3D=3D 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
>=20
> Online demo: https://gcc.godbolt.org/z/3W5onY955

That is unrelated and gcc is actually correct there see pr 99637.=