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PR libstdc++/86751 default assignment operators for std::pair

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The solution for PR 77537 causes ambiguities due to the extra copy
assignment operator taking a __nonesuch_no_braces parameter. By making
the base class non-assignable we don't need the extra deleted overload
in std::pair. The copy assignment operator will be implicitly deleted
(and the move assignment operator not declared) as needed. Without the
additional user-provided operator in std::pair the ambiguity is avoided.

	PR libstdc++/86751
	* include/bits/stl_pair.h (__pair_base): New class with deleted copy
	assignment operator.
	(pair): Derive from __pair_base.
	(pair::operator=): Remove deleted overload.
	* python/libstdcxx/v6/printers.py (StdPairPrinter): New pretty printer
	so that new base class isn't shown in GDB.
	* testsuite/20_util/pair/86751.cc: New test.
	* testsuite/20_util/pair/ref_assign.cc: New test.

From-SVN: r263185
This commit is contained in:
Jonathan Wakely 2018-07-31 23:31:20 +01:00 • committed by Jonathan Wakely
parent ff27340046
commit e182158261
5 changed files with 164 additions and 8 deletions
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10
libstdc++-v3/ChangeLog
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@ -1,5 +1,15 @@
2018-07-31 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/86751
* include/bits/stl_pair.h (__pair_base): New class with deleted copy
assignment operator.
(pair): Derive from __pair_base.
(pair::operator=): Remove deleted overload.
* python/libstdcxx/v6/printers.py (StdPairPrinter): New pretty printer
so that new base class isn't shown in GDB.
* testsuite/20_util/pair/86751.cc: New test.
* testsuite/20_util/pair/ref_assign.cc: New test.
* include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP)
(_GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE): Move definitions here.
(_GLIBCXX_HAVE_BUILTIN_LAUNDER): Likewise. Use !__is_identifier

21
libstdc++-v3/include/bits/stl_pair.h
View file

@ -185,8 +185,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __nonesuch_no_braces : std::__nonesuch {
explicit __nonesuch_no_braces(const __nonesuch&) = delete;
};
#endif // C++11
#endif
class __pair_base
{
#if __cplusplus >= 201103L
template<typename _T1, typename _T2> friend struct pair;
__pair_base() = default;
~__pair_base() = default;
__pair_base(const __pair_base&) = default;
__pair_base& operator=(const __pair_base&) = delete;
#endif // C++11
};
/**
* @brief Struct holding two objects of arbitrary type.
@ -196,6 +206,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
template<typename _T1, typename _T2>
struct pair
: private __pair_base
{
typedef _T1 first_type; /// @c first_type is the first bound type
typedef _T2 second_type; /// @c second_type is the second bound type
@ -374,19 +385,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
pair&
operator=(typename conditional<
__not_<__and_<is_copy_assignable<_T1>,
is_copy_assignable<_T2>>>::value,
const pair&, const __nonesuch_no_braces&>::type __p) = delete;
pair&
operator=(typename conditional<
__and_<is_move_assignable<_T1>,
is_move_assignable<_T2>>::value,
pair&&, __nonesuch_no_braces&&>::type __p)
noexcept(__and_<is_nothrow_move_assignable<_T1>,
is_nothrow_move_assignable<_T2>>::value)
is_nothrow_move_assignable<_T2>>::value)
{
first = std::forward<first_type>(__p.first);
second = std::forward<second_type>(__p.second);

34
libstdc++-v3/python/libstdcxx/v6/printers.py
View file

@ -1229,6 +1229,39 @@ class StdExpPathPrinter:
return self._iterator(self.val['_M_cmpts'])
class StdPairPrinter:
"Print a std::pair object, with 'first' and 'second' as children"
def __init__(self, typename, val):
self.val = val
class _iter(Iterator):
"An iterator for std::pair types. Returns 'first' then 'second'."
def __init__(self, val):
self.val = val
self.which = 'first'
def __iter__(self):
return self
def __next__(self):
if self.which is None:
raise StopIteration
which = self.which
if which == 'first':
self.which = 'second'
else:
self.which = None
return (which, self.val[which])
def children(self):
return self._iter(self.val)
def to_string(self):
return None
# A "regular expression" printer which conforms to the
# "SubPrettyPrinter" protocol from gdb.printing.
class RxPrinter(object):
@ -1629,6 +1662,7 @@ def build_libstdcxx_dictionary ():
libstdcxx_printer.add_container('std::', 'map', StdMapPrinter)
libstdcxx_printer.add_container('std::', 'multimap', StdMapPrinter)
libstdcxx_printer.add_container('std::', 'multiset', StdSetPrinter)
libstdcxx_printer.add_version('std::', 'pair', StdPairPrinter)
libstdcxx_printer.add_version('std::', 'priority_queue',
StdStackOrQueuePrinter)
libstdcxx_printer.add_version('std::', 'queue', StdStackOrQueuePrinter)

33
libstdc++-v3/testsuite/20_util/pair/86751.cc Normal file
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@ -0,0 +1,33 @@
// Copyright (C) 2018 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++11 } }
#include <utility>
struct X {
template<typename T> operator T() const;
};
void
test01()
{
std::pair<int, int> p;
X x;
p = x; // PR libstdc++/86751
}

74
libstdc++-v3/testsuite/20_util/pair/ref_assign.cc Normal file
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@ -0,0 +1,74 @@
// Copyright (C) 2018 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 run { target c++11 } }
#include <utility>
#include <testsuite_hooks.h>
void
test01()
{
typedef std::pair<int&, int> pair_type;
int i = 1;
int j = 2;
pair_type p(i, 3);
const pair_type q(j, 4);
p = q;
VERIFY( p.first == q.first );
VERIFY( p.second == q.second );
VERIFY( i == j );
}
void
test02()
{
typedef std::pair<int, int&> pair_type;
int i = 1;
int j = 2;
pair_type p(3, i);
const pair_type q(4, j);
p = q;
VERIFY( p.first == q.first );
VERIFY( p.second == q.second );
VERIFY( i == j );
}
void
test03()
{
typedef std::pair<int&, int&> pair_type;
int i = 1;
int j = 2;
int k = 3;
int l = 4;
pair_type p(i, j);
const pair_type q(k, l);
p = q;
VERIFY( p.first == q.first );
VERIFY( p.second == q.second );
VERIFY( i == k );
VERIFY( j == l );
}
int
main()
{
test01();
test02();
test03();
}