From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 141AB3858D28; Tue, 12 Apr 2022 21:13:48 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 141AB3858D28 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r11-9837] libstdc++: Prevent -Wstringop-overread warning in std::deque [PR100516] X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/releases/gcc-11 X-Git-Oldrev: 5ede37c0f274f0de19afd662588891e32b60f705 X-Git-Newrev: 573bb865df967b420aba5382a5987b8865f83dc0 Message-Id: <20220412211348.141AB3858D28@sourceware.org> Date: Tue, 12 Apr 2022 21:13:48 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Apr 2022 21:13:48 -0000 https://gcc.gnu.org/g:573bb865df967b420aba5382a5987b8865f83dc0 commit r11-9837-g573bb865df967b420aba5382a5987b8865f83dc0 Author: Jonathan Wakely Date: Thu Jan 27 22:31:26 2022 +0000 libstdc++: Prevent -Wstringop-overread warning in std::deque [PR100516] The compiler warns about the loop in deque::_M_range_initialize because it doesn't know that the number of nodes has already been correctly sized to match the size of the input. Use __builtin_unreachable to tell it that the loop will never be entered if the number of elements is smaller than a single node. libstdc++-v3/ChangeLog: PR libstdc++/100516 * include/bits/deque.tcc (_M_range_initialize): Add __builtin_unreachable to loop. * testsuite/23_containers/deque/100516.cc: New test. (cherry picked from commit eae41b4d2cc30327f9f15c7390438c46aa09ed3f) Diff: --- libstdc++-v3/include/bits/deque.tcc | 3 +++ libstdc++-v3/testsuite/23_containers/deque/100516.cc | 14 ++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/libstdc++-v3/include/bits/deque.tcc b/libstdc++-v3/include/bits/deque.tcc index db532e3c585..13c0f8a2be3 100644 --- a/libstdc++-v3/include/bits/deque.tcc +++ b/libstdc++-v3/include/bits/deque.tcc @@ -454,6 +454,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER __cur_node < this->_M_impl._M_finish._M_node; ++__cur_node) { + if (__n < _S_buffer_size()) + __builtin_unreachable(); // See PR 100516 + _ForwardIterator __mid = __first; std::advance(__mid, _S_buffer_size()); std::__uninitialized_copy_a(__first, __mid, *__cur_node, diff --git a/libstdc++-v3/testsuite/23_containers/deque/100516.cc b/libstdc++-v3/testsuite/23_containers/deque/100516.cc new file mode 100644 index 00000000000..ef32ae10545 --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/deque/100516.cc @@ -0,0 +1,14 @@ +// { dg-options "-O2 -Wstringop-overread" } +// { dg-do compile { target c++11 } } + +// Bug 100516 +// Unexpected -Wstringop-overread in deque initialization from empty +// initializer_list + +#include + +void f() +{ + std::initializer_list il{}; + std::deque{il}; +}