[Bug c++/71675] __atomic_compare_exchange_n returns wrong type for typed enum

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71675

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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           Keywords|documentation               |rejects-valid

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
You're right.  I was mistaken in comment #1 about the return value: the
function does return a true/false result, but it appears to be of the wrong
type.  So the documentation is correct (it matches C11 atomic_compare_exchange)
and the bug is in the compiler.

The root cause seems to be the resolve_overloaded_builtin function in
builtins.c calling sync_resolve_return to convert the bool result to the enum,
which the C++ front end then rejects.