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([2a01:e0a:1dc:b1c0:f5e4:e9bf:70b3:4a52]) by smtp.googlemail.com with ESMTPSA id f24sm16292564wmb.32.2021.04.18.06.28.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Apr 2021 06:28:15 -0700 (PDT) Subject: Re: [Bug libstdc++/99402] [10 Regression] std::copy creates _GLIBCXX_DEBUG false positive for attempt to subscript a dereferenceable (start-of-sequence) iterator To: "libstdc++@gcc.gnu.org" , gcc-patches References: From: =?UTF-8?Q?Fran=c3=a7ois_Dumont?= Message-ID: <70f13ddf-8b3a-1a6b-006f-21a9cb3a5db9@gmail.com> Date: Sun, 18 Apr 2021 15:28:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------9034FC4F7E3F1EA5627D768D" Content-Language: fr X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 18 Apr 2021 13:28:21 -0000 This is a multi-part message in MIME format. --------------9034FC4F7E3F1EA5627D768D Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Hi     Ok to backport this to gcc-10 branch ?     Tested under Linux x86_64. François On 13/04/21 10:51 pm, redi at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99402 > > Jonathan Wakely changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > Summary|[10/11 Regression] |[10 Regression] std::copy > |std::copy creates |creates _GLIBCXX_DEBUG > |_GLIBCXX_DEBUG false |false positive for attempt > |positive for attempt to |to subscript a > |subscript a dereferenceable |dereferenceable > |(start-of-sequence) |(start-of-sequence) > |iterator |iterator > > --- Comment #10 from Jonathan Wakely --- > This was fixed on trunk by r11-8100: > > libstdc++: [_GLIBCXX_DEBUG] Fix management of __dp_sign_max_size [PR 99402] > > __dp_sign precision indicates that we found out what iterator comes first or > last in the range. __dp_sign_max_size is the same plus it gives the information > of the max size of the range that is to say the max_size value such that > distance(lhs, rhs) < max_size. > Thanks to this additional information we are able to tell when a copy of n > elements > to that range will fail even if we do not know exactly how large it is. > > This patch makes sure that we are properly using this information. > > libstdc++-v3/ChangeLog: > > PR libstdc++/99402 > * include/debug/helper_functions.h (__can_advance(_InputIterator, > const std::pair<_Diff, _Distance_precision>&, int)): New. > (__can_advance(const _Safe_iterator<>&, > const std::pair<_Diff, _Distance_precision>&, int)): New. > * include/debug/macros.h (__glibcxx_check_can_increment_dist): New, > use latter. > (__glibcxx_check_can_increment_range): Adapt to use latter. > (__glibcxx_check_can_decrement_range): Likewise. > * include/debug/safe_iterator.h > (_Safe_iterator<>::_M_can_advance(const std::pair<_Diff, > _Distance_precision>&, > int)): New. > (__can_advance(const _Safe_iterator<>&, > const std::pair<_Diff, _Distance_precision>&, int)): New. > * include/debug/safe_iterator.tcc > (_Safe_iterator<>::_M_can_advance(const std::pair<_Diff, > _Distance_precision>&, > int)): New. > (_Safe_iterator<>::_M_valid_range(const _Safe_iterator<>&, > std::pair&, bool)): Adapt for > __dp_sign_max_size. > (__copy_move_a): Adapt to use __glibcxx_check_can_increment_dist. > (__copy_move_backward_a): Likewise. > (__equal_aux): Likewise. > * include/debug/stl_iterator.h (__can_advance(const > std::reverse_iterator<>&, > const std::pair<_Diff, _Distance_precision>&, int)): New. > (__can_advance(const std::move_iterator<>&, > const std::pair<_Diff, _Distance_precision>&, int)): New. > * testsuite/25_algorithms/copy/debug/99402.cc: New test. > --------------9034FC4F7E3F1EA5627D768D Content-Type: text/x-patch; charset=UTF-8; name="pr99402.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="pr99402.patch" diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h index 62d5309257f..9e2d206f06c 100644 --- a/libstdc++-v3/include/debug/helper_functions.h +++ b/libstdc++-v3/include/debug/helper_functions.h @@ -64,7 +64,7 @@ namespace __gnu_debug { private: typedef - typename std::iterator_traits<_Iterator>::difference_type _ItDiffType; + typename std::iterator_traits<_Iterator>::difference_type _ItDiffType; template::__type> @@ -287,6 +287,18 @@ namespace __gnu_debug __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&, _Size); + template + _GLIBCXX_CONSTEXPR + inline bool + __can_advance(_InputIterator, const std::pair<_Diff, _Distance_precision>&, int) + { return true; } + + template + bool + __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&, + const std::pair<_Diff, _Distance_precision>&, int); + /** Helper function to extract base iterator of random access safe iterator * in order to reduce performance impact of debug mode. Limited to random * access iterator because it is the only category for which it is possible diff --git a/libstdc++-v3/include/debug/macros.h b/libstdc++-v3/include/debug/macros.h index 73fb50d0cbd..1f45f8e0adc 100644 --- a/libstdc++-v3/include/debug/macros.h +++ b/libstdc++-v3/include/debug/macros.h @@ -104,6 +104,12 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \ ._M_iterator(_First, #_First) \ ._M_integer(_Size, #_Size)) +#define __glibcxx_check_can_increment_dist(_First,_Dist,_Way) \ + _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Dist, _Way), \ + _M_message(__gnu_debug::__msg_iter_subscript_oob) \ + ._M_iterator(_First, #_First) \ + ._M_integer(_Way * _Dist.first, #_Dist)) + #define __glibcxx_check_can_increment_range(_First1,_Last1,_First2) \ do \ { \ @@ -115,7 +121,7 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \ ._M_iterator(_Last1, #_Last1), \ __FILE__,__LINE__,__PRETTY_FUNCTION__); \ _GLIBCXX_DEBUG_VERIFY_COND_AT( \ - __gnu_debug::__can_advance(_First2, __dist.first),\ + __gnu_debug::__can_advance(_First2, __dist, 1), \ _M_message(__gnu_debug::__msg_iter_subscript_oob)\ ._M_iterator(_First2, #_First2) \ ._M_integer(__dist.first), \ @@ -133,7 +139,7 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \ ._M_iterator(_Last1, #_Last1), \ __FILE__,__LINE__,__PRETTY_FUNCTION__); \ _GLIBCXX_DEBUG_VERIFY_COND_AT( \ - __gnu_debug::__can_advance(_First2, -__dist.first),\ + __gnu_debug::__can_advance(_First2, __dist, -1), \ _M_message(__gnu_debug::__msg_iter_subscript_oob)\ ._M_iterator(_First2, #_First2) \ ._M_integer(-__dist.first), \ diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h index 687b844fd75..2f51618dd88 100644 --- a/libstdc++-v3/include/debug/safe_iterator.h +++ b/libstdc++-v3/include/debug/safe_iterator.h @@ -405,6 +405,12 @@ namespace __gnu_debug bool _M_can_advance(difference_type __n, bool __strict = false) const; + // Can we advance the iterator using @p __dist in @p __way direction. + template + bool + _M_can_advance(const std::pair<_Diff, _Distance_precision>& __dist, + int __way) const; + // Is the iterator range [*this, __rhs) valid? bool _M_valid_range(const _Safe_iterator& __rhs, @@ -956,6 +962,14 @@ namespace __gnu_debug _Size __n) { return __it._M_can_advance(__n); } + template + inline bool + __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>& __it, + const std::pair<_Diff, _Distance_precision>& __dist, + int __way) + { return __it._M_can_advance(__dist, __way); } + template _Iterator __base(const _Safe_iterator<_Iterator, _Sequence, diff --git a/libstdc++-v3/include/debug/safe_iterator.tcc b/libstdc++-v3/include/debug/safe_iterator.tcc index 312a88911ee..79a8ee28d97 100644 --- a/libstdc++-v3/include/debug/safe_iterator.tcc +++ b/libstdc++-v3/include/debug/safe_iterator.tcc @@ -92,24 +92,32 @@ namespace __gnu_debug if (__n == 0) return true; + std::pair __dist = __n < 0 + ? _M_get_distance_from_begin() + : _M_get_distance_to_end(); + if (__n < 0) - { - std::pair __dist = - _M_get_distance_from_begin(); - return __dist.second == __dp_exact - ? __dist.first >= -__n - : !__strict && __dist.first > 0; - } - else - { - std::pair __dist = - _M_get_distance_to_end(); - return __dist.second == __dp_exact - ? __dist.first >= __n - : !__strict && __dist.first > 0; - } + __n = -__n; + + return __dist.second > __dp_sign + ? __dist.first >= __n + : !__strict && __dist.first > 0; } + template + template + bool + _Safe_iterator<_Iterator, _Sequence, _Category>:: + _M_can_advance(const std::pair<_Diff, _Distance_precision>& __dist, + int __way) const + { + return __dist.second == __dp_exact + ? _M_can_advance(__way * __dist.first) + : _M_can_advance(__way * (__dist.first == 0 + ? 0 + : __dist.first < 0 ? -1 : 1)); + } + template typename _Distance_traits<_Iterator>::__type _Safe_iterator<_Iterator, _Sequence, _Category>:: @@ -191,19 +199,12 @@ namespace __gnu_debug /* Determine iterators order */ __dist = _M_get_distance_to(__rhs); - switch (__dist.second) + if (__dist.second != __dp_equality) { - case __dp_equality: - if (__dist.first == 0) - return true; - break; - - case __dp_sign: - case __dp_exact: // If range is not empty first iterator must be dereferenceable. - if (__dist.first > 0) - return !__check_dereferenceable || _M_dereferenceable(); - return __dist.first == 0; + return __dist.first == 0 + || (__dist.first > 0 + && (!__check_dereferenceable || _M_dereferenceable())); } // Assume that this is a valid range; we can't check anything else. @@ -224,9 +225,8 @@ namespace __gnu_debug __dist = std::make_pair(__rhs.base() - this->base(), __dp_exact); // If range is not empty first iterator must be dereferenceable. - if (__dist.first > 0) - return this->_M_dereferenceable(); - return __dist.first == 0; + return __dist.first == 0 + || (__dist.first > 0 && this->_M_dereferenceable()); } } // namespace __gnu_debug @@ -244,7 +244,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_Ite>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, __dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_equality) return std::__copy_move_a<_IsMove>(__first.base(), __last.base(), @@ -261,7 +261,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_II>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, __dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_sign && __result._M_can_advance(__dist.first, true)) @@ -283,7 +283,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_IIte>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, __dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_equality) { @@ -311,7 +311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_Ite>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, -__dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, -1); if (__dist.second > ::__gnu_debug::__dp_equality) return std::__copy_move_backward_a<_IsMove>( @@ -328,7 +328,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_II>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, -__dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, -1); if (__dist.second > ::__gnu_debug::__dp_sign && __result._M_can_advance(-__dist.first, true)) @@ -351,7 +351,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_IIte>::__type __dist; __glibcxx_check_valid_range2(__first, __last, __dist); - __glibcxx_check_can_increment(__result, -__dist.first); + __glibcxx_check_can_increment_dist(__result, __dist, -1); if (__dist.second > ::__gnu_debug::__dp_equality) { @@ -416,7 +416,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist; __glibcxx_check_valid_range2(__first1, __last1, __dist); - __glibcxx_check_can_increment(__first2, __dist.first); + __glibcxx_check_can_increment_dist(__first2, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_equality) return std::__equal_aux(__first1.base(), __last1.base(), __first2); @@ -431,7 +431,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist; __glibcxx_check_valid_range2(__first1, __last1, __dist); - __glibcxx_check_can_increment(__first2, __dist.first); + __glibcxx_check_can_increment_dist(__first2, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_sign && __first2._M_can_advance(__dist.first, true)) @@ -450,7 +450,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist; __glibcxx_check_valid_range2(__first1, __last1, __dist); - __glibcxx_check_can_increment(__first2, __dist.first); + __glibcxx_check_can_increment_dist(__first2, __dist, 1); if (__dist.second > ::__gnu_debug::__dp_equality) { diff --git a/libstdc++-v3/include/debug/stl_iterator.h b/libstdc++-v3/include/debug/stl_iterator.h index 6044f3588d9..02adb6e3c06 100644 --- a/libstdc++-v3/include/debug/stl_iterator.h +++ b/libstdc++-v3/include/debug/stl_iterator.h @@ -52,6 +52,13 @@ namespace __gnu_debug __can_advance(const std::reverse_iterator<_Iterator>& __it, _Size __n) { return __can_advance(__it.base(), -__n); } + template + inline bool + __can_advance(const std::reverse_iterator<_Iterator>& __it, + const std::pair<_Diff, _Distance_precision>& __dist, + int __way) + { return __can_advance(__it.base(), __dist, -__way); } + template inline std::reverse_iterator<_Iterator> __base(const std::reverse_iterator<_Safe_iterator< @@ -101,6 +108,13 @@ namespace __gnu_debug __can_advance(const std::move_iterator<_Iterator>& __it, _Size __n) { return __can_advance(__it.base(), __n); } + template + inline bool + __can_advance(const std::move_iterator<_Iterator>& __it, + const std::pair<_Diff, _Distance_precision>& __dist, + int __way) + { return __can_advance(__it.base(), __dist, __way); } + template inline auto __unsafe(const std::move_iterator<_Iterator>& __it) diff --git a/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc b/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc new file mode 100644 index 00000000000..041d222d079 --- /dev/null +++ b/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc @@ -0,0 +1,35 @@ +// Copyright (C) 2021 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 +// . + +// { dg-options "-D_GLIBCXX_DEBUG" } +// { dg-do run } + +#include +#include +#include + +// PR libstdc++/99402 + +using namespace std; + +int main() +{ + // any container with non-random access iterators: + const set source = { 0, 1 }; + vector dest(1); + copy(source.begin(), ++source.begin(), dest.begin()); +} --------------9034FC4F7E3F1EA5627D768D--