[Bug libstdc++/114865] [13/14/15 Regression] std::atomic::compare_exchange_strong seems to hang under GCC 13 for C++11

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114865

--- Comment #23 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #22)
> I'm not sure how to fix that problem without pessimizing every
> std::atomic<T>::compare_exchange_strong to use the looping implementation

To be clear, not *every* compare exchange, only when T has padding bits.

Which suggests you would get better perf by defining your type to have no
padding bits:

struct state_type
{
    std::uint64_t timestamp;
    std::uint16_t clock_seq;
    char unused[6];
};