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From: "de34 at live dot cn" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/108974] std::barrier except completion function which
 is not manifestly noexcept
Date: Thu, 02 Mar 2023 02:27:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108974

Jiang An <de34 at live dot cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |de34 at live dot cn

--- Comment #3 from Jiang An <de34 at live dot cn> ---
> 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...=