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Add [[nodiscard]] attribute to std::launder

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* libsupc++/new (launder): Add nodiscard attribute.
	* testsuite/18_support/launder/nodiscard.cc: New test.

From-SVN: r255127
This commit is contained in:
Jonathan Wakely 2017-11-24 00:00:46 +00:00 • committed by Jonathan Wakely
parent 117e6b50b6
commit a8541d9021
3 changed files with 34 additions and 2 deletions
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3
libstdc++-v3/ChangeLog
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@ -1,5 +1,8 @@
2017-11-23 Jonathan Wakely <jwakely@redhat.com>
* libsupc++/new (launder): Add nodiscard attribute.
* testsuite/18_support/launder/nodiscard.cc: New test.
* include/bits/fs_path.h (path::empty): Add nodiscard attribute.
* include/bits/range_access.h (empty): Likewise.
* include/std/string_view (basic_string_view::empty): Likewise.

4
libstdc++-v3/libsupc++/new
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@ -176,7 +176,7 @@ inline void operator delete[](void*, void*) _GLIBCXX_USE_NOEXCEPT { }
//@}
} // extern "C++"
#if __cplusplus > 201402L
#if __cplusplus >= 201703L
#if __GNUC__ >= 7
# define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
#elif defined __has_builtin
@ -192,7 +192,7 @@ namespace std
#define __cpp_lib_launder 201606
/// Pointer optimization barrier [ptr.launder]
template<typename _Tp>
constexpr _Tp*
[[nodiscard]] constexpr _Tp*
launder(_Tp* __p) noexcept
{ return __builtin_launder(__p); }

29
libstdc++-v3/testsuite/18_support/launder/nodiscard.cc Normal file
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@ -0,0 +1,29 @@
// Copyright (C) 2017 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-options "-std=gnu++17" }
// { dg-do compile { target c++17 } }
#include <new>
struct A { const int i; };
void
test01(A* a)
{
std::launder(a); // { dg-warning "ignoring return value" }
}