https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108974
--- Comment #4 from Thomas Rodgers <rodgertq at gcc dot gnu.org> --- (In reply to Jiang An from comment #3) > > is_nothrow_invocable_v<CompletionFunction&> shall be true. > > If implementation divergence is not intendedly permitted, I don't think it > makes much sense to introduce UB in this way. > > I guess we should either turn it into a mandating requirement: > > Instantiation of barrier<CompletionFunction> is ill-formed > > if is_nothrow_invocable_v<CompletionFunction&> is not true. > > Or relax the preconditions: > > If any invocation to the completion function throws an exception, > > the behavior is undefined. > > I've mailed to LWG Chair for this... LWG Chair has already weighed in on this thread. libstdc++ and libc++ have essentially the same implementation of std::barrier (libstdc++'s implementation is derived from libc++'s). So that they behave consistently and MSVC is different is not surprising. I don't have a strong opinion on whether this should be UB ore mandated. Raising an LWG issue seems reasonable.
