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libstdc++: Fix ambiguous comparisons in __gnu_debug::bitset [PR 96303]

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With -pedantic the debug mode bitset has an ambiguous equality
comparison operator, because it tries to compare the non-debug base to
the debug object. The base object can be converted to another debug
bitset, making the same operator== a candidate again.

The fix is to do the comparison on both base objects, so the operator
for the derived type isn't a candidate.

For the inequality operator the same change should be done, but that
operator can be removed entirely for C++20 because it can be synthesized
by the compiler.

I don't think either equality or inequality operators are really needed,
because the public _GLIBCXX_STD_C::bitset base class cam always be
compared using its own comparison operators. I'm not changing that here
though.

libstdc++-v3/ChangeLog:

	PR libstdc++/96303
	* include/debug/bitset (bitset::operator==): Call _M_base() on
	right operand.
	(bitset::operator!=): Likewise, but don't define it at all when
	default comparisons are supported by the compiler.
	* testsuite/23_containers/bitset/operations/96303.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-08-07 20:29:11 +01:00
parent a1ee6d507b
commit de1e3b8795
2 changed files with 35 additions and 2 deletions
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6
libstdc++-v3/include/debug/bitset
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@ -353,11 +353,13 @@ namespace __debug
bool
operator==(const bitset<_Nb>& __rhs) const _GLIBCXX_NOEXCEPT
{ return _M_base() == __rhs; }
{ return _M_base() == __rhs._M_base(); }
#if __cpp_impl_three_way_comparison < 201907L
bool
operator!=(const bitset<_Nb>& __rhs) const _GLIBCXX_NOEXCEPT
{ return _M_base() != __rhs; }
{ return _M_base() != __rhs._M_base(); }
#endif
using _Base::test;
using _Base::all;

31
libstdc++-v3/testsuite/23_containers/bitset/operations/96303.cc Normal file
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@ -0,0 +1,31 @@
// 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-options "-std=gnu++2a -pedantic" }
// { dg-do compile { target c++2a } }
#include <debug/bitset>
bool
test01()
{
__gnu_debug::bitset<1> b;
// PR libstdc++/96303
bool eq = b == b;
bool ne = b != b;
return eq && !ne;
}