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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/103755] {has,use}_facet() and iostream constructor
 performance
Date: Fri, 17 Dec 2021 17:22:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103755

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Created attachment 52024
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52024&action=3Dedit
Alternative implementation

This seems like a much simpler approach.

This causes 22_locale/ctype/is/string/89728_neg.cc to fail for C++98/11/14
modes, because without 'if constexpr' the body of __try_use_facet creates
dozens of errors, rather than just one from the current definition of
use_facet. That isn't the end of the world, but it's a regression in diagno=
stic
quality.=