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libstdc++: Make _GLIBCXX_CONCEPT_CHECKS more constexpr-friendly

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Although most of the old-style "concept checks" are only really usable
with C++98 because they enforce the wrong things, this is a simple
change that makes them a bit more useful for C++14 and up.

	* include/bits/boost_concept_check.h (__function_requires): Add
	_GLIBCXX14_CONSTEXPR.
	* testsuite/25_algorithms/min/concept_checks.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-02-27 10:52:28 +00:00
parent d121530468
commit eb8e6a30a4
3 changed files with 30 additions and 1 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2020-02-27 Jonathan Wakely <jwakely@redhat.com>
* include/bits/boost_concept_check.h (__function_requires): Add
_GLIBCXX14_CONSTEXPR.
* testsuite/25_algorithms/min/concept_checks.cc: New test.
2020-02-26 Patrick Palka <ppalka@redhat.com>
PR libstdc++/93936

2
libstdc++-v3/include/bits/boost_concept_check.h
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@ -57,7 +57,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// as possible at runtime, use as few resources as possible, and hopefully
// be elided out of existence... hmmm.
template <class _Concept>
inline void __function_requires()
_GLIBCXX14_CONSTEXPR inline void __function_requires()
{
void (_Concept::*__x)() _IsUnused = &_Concept::__constraints;
}

23
libstdc++-v3/testsuite/25_algorithms/min/concept_checks.cc Normal file
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@ -0,0 +1,23 @@
// Copyright (C) 2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-do compile { target c++14 } }
#define _GLIBCXX_CONCEPT_CHECKS 1
#include <algorithm>
constexpr int i = std::min(1, 2);