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libstdc++: Fix std::to_address for debug iterators (PR 93960) 

It should be valid to use std::to_address on a past-the-end iterator,
but the debug mode iterators do a check for dereferenceable in their
operator->(). That check is generally useful, so rather than remove it
this changes std::__to_address to identify a debug mode iterator and
use base().operator->() to skip the check.

Backport from mainline
2020-04-03  Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/93960
	* include/bits/ptr_traits.h (__to_address): Add special case for debug
	iterators, to avoid dereferenceable check.
	* testsuite/20_util/to_address/1_neg.cc: Adjust dg-error line number.
	* testsuite/20_util/to_address/debug.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-04-03 12:00:07 +01:00
parent 69df6742cb
commit b20b7f7e88
4 changed files with 58 additions and 2 deletions
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11
libstdc++-v3/ChangeLog
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@ -1,3 +1,14 @@
2020-04-03 Jonathan Wakely <jwakely@redhat.com>
Backport from mainline
2020-04-03 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/93960
* include/bits/ptr_traits.h (__to_address): Add special case for debug
iterators, to avoid dereferenceable check.
* testsuite/20_util/to_address/1_neg.cc: Adjust dg-error line number.
* testsuite/20_util/to_address/debug.cc: New test.
2020-03-16 Jonathan Wakely <jwakely@redhat.com>
Backport from mainline

11
libstdc++-v3/include/bits/ptr_traits.h
View File

@ -34,6 +34,10 @@
#include <bits/move.h>
#if __cplusplus > 201703L
namespace __gnu_debug { struct _Safe_iterator_base; }
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@ -169,7 +173,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Ptr, typename... _None>
constexpr auto
__to_address(const _Ptr& __ptr, _None...) noexcept
{ return std::__to_address(__ptr.operator->()); }
{
if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>)
return std::__to_address(__ptr.base().operator->());
else
return std::__to_address(__ptr.operator->());
}
/**
* @brief Obtain address referenced by a pointer to an object

2
libstdc++-v3/testsuite/20_util/to_address/1_neg.cc
View File

@ -17,7 +17,7 @@
// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }
// { dg-error "not a function pointer" "" { target *-*-* } 153 }
// { dg-error "not a function pointer" "" { target *-*-* } 157 }
#include <memory>

36
libstdc++-v3/testsuite/20_util/to_address/debug.cc Normal file
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@ -0,0 +1,36 @@
// 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" }
// { dg-do run { target c++2a } }
#include <debug/vector>
#include <testsuite_hooks.h>
void
test01()
{
__gnu_debug::vector<int> v{1, 2, 3};
auto p = std::to_address(v.end());
VERIFY( p == v.data() + v.size() );
}
int
main()
{
test01();
}