[Bug libstdc++/102567] Missing noexcept specialization of std::function

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102567

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Florian Weimer from comment #3)
> (In reply to Jonathan Wakely from comment #1)
> > This is not a libstdc++ bug, we implement what the standard says.
> > 
> > Maybe it used to compile, but it was meaningless. You could say it was a
> > function of void() noexcept, but you could still store a target function
> > that throwed, and its operator() could still throw.
> 
> Sure, but in my code, I did not do this. The call operator was invoked in a
> noexcept context, and the type was expected to match (but of course the
> compiler did not check this).

Then you need to stop doing it, the C++17 changes make it no longer possible to
use that extra annotation in the type to signify something that wasn't checked,
or even necessarily true.

> Neither paper seems to cover a polymorphic function type that takes
> ownership, though, so I don't quite see how these replace std::function.

They're not supposed to replace it, they supplement it for additional scenarios
(non-owning, or owning a movable but non-copyable target).

My point is just that the newer facilities being added do allow you to use
noexcept the way you want to, but std::function doesn't. And I doubt anybody is
going to propose extending it that way.

Either way, it's not a libstdc++ bug.