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Subject: [Bug c++/104386] no_unique_address causes invalid member alignment
 of pod struct
Date: Sun, 06 Feb 2022 10:26:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104386

--- Comment #2 from Artur Ba=C4=87 <gcc at ebasoft dot com.pl> ---
I think it is connected with this case

https://godbolt.org/z/cvfs1KqGW
https://godbolt.org/z/vdzTzo7be

//sizeof(foo) =3D=3D12
struct base
{
uint32_t x{};
std::byte v{};

base() noexcept =3D default;
};

struct foo : public base
{
std::byte z;
};

//sizeof(foo) =3D=3D 8
struct base
{
uint32_t x;
std::byte v;

base() noexcept : x{}, v{} {}
};

struct foo : public base
{
std::byte z;
};

and

https://www.reddit.com/r/cpp/comments/slfugx/comment/hvs4n7j/?utm_source=3D=
share&utm_medium=3Dweb2x&context=3D3

"Som1Lse =C2=B7 5 hr. ago

Interestingly GCC disagrees with itself:

    -std=3Dc++17 it considers base to be a POD and doesn't reuse padding.
    -std=3Dc++20 it considers base to not be a POD and agrees with Clang, r=
eusing
the padding bytes."=