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From: "arthur.j.odwyer at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/115497] [15 Regression] __is_pointer doesn't compile
 with clang since 014879ea4c86b3b8ab6b61a1226ee5b31e816c8b
Date: Sat, 15 Jun 2024 12:58:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115497

Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |arthur.j.odwyer at gmail d=
ot com

--- Comment #8 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
FWIW, I also ran into this, this morning.
Reduced: https://godbolt.org/z/rxYKTqKd4
Organically in Abseil: https://godbolt.org/z/9eoqKzYjc
(This happens because Abseil #includes <algorithm> before <type_traits>
(alphabetically). If you switch the order of those two includes, it Just
Works.)

IMVHO libstdc++ should do jwakely's idea of #include <type_traits> from the
offending header file; that's the most foolproof O(1) solution, rather than=
 the
O(N) solution of being really careful to always write `bool(__is_foo(T))`
instead of `__is_foo(T)`. Also, there are definitely third-party libraries
(like Abseil) out there who legitimately want to use `__is_pointer(T)` in t=
heir
own code, and right now they have no idea that they ought to write all their
uses with an extra `bool` cast just to work around a problematic interaction
between Clang and libstdc++ (a mode they probably don't even build in their
CI). So fixing the problem once and for all on libstdc++'s side of the fence
would be really helpful.=