[Bug libstdc++/121148] Should use modular arithmetic for _Atomic_word

[schwab--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121148

--- Comment #12 from Andreas Schwab <sch...@linux-m68k.org> ---
(In reply to Jonathan Wakely from comment #4)
The cpu does not care about overflow, of course, apart from setting the V bit
in the CC.