From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id EFC923857C46; Thu, 4 Jan 2024 20:45:36 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org EFC923857C46 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1704401136; bh=V/2c5goyaJgt7hDeJmKcYPvpIGw0nTxoZ7FhM93gMYA=; h=From:To:Subject:Date:From; b=BzVZ/fUsx+KImvhnncnr9m4TnLTsf9YkniwvV3WdwSvRlSUJB1b8o7TYqpugZeAXE 0Zd5/YuIF8OTOaEFdAQxltecQEap7pqZD/7iqann7tHRAFr6fBolb+vI/NKTQE55hY tdjkqhUCDgdzWLZuzjn4Y1/V7MSK7kbNrGZhsCEQ= From: "dimitry@unified-streaming.com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/113239] New: [13 regression] After 822a11a1e64, bogus -Warray-bounds warnings in std::vector Date: Thu, 04 Jan 2024 20:45:34 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 14.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: dimitry@unified-streaming.com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113239 Bug ID: 113239 Summary: [13 regression] After 822a11a1e64, bogus -Warray-bounds warnings in std::vector Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: dimitry@unified-streaming.com Target Milestone: --- We noticed spurious warnings in some C++17 code compiled with g++ 13.2.0, a= nd I bisected it to commit 822a11a1e642e0abe92a996e7033a5066905a447 ("libstdc++:= Do not use memmove for 1-element ranges [PR108846]") for bug 108846 ("std::cop= y, std::copy_n and std::copy_backward on potentially overlapping subobjects"). Reduced test case: // g++ -std=3Dc++17 -Wall -O2 -c testcase.cpp #include #include struct frame_t { uint64_t pts_; uint32_t timescale_; std::vector data_; }; struct frame_source_t { virtual frame_t get() =3D 0; }; struct frame_filter_t : frame_source_t { frame_t get() override { if(current_frame_.data_.empty()) { return current_frame_; } else { return frame_t(); } } frame_t current_frame_; }; frame_filter_t create_frame_filter() { return frame_filter_t(); } // EOT With gcc-13-6371-ga41a56dee5c, this compiles without any warning. With gcc-13-6372-g822a11a1e64 and later, up to gcc-14-6924-g00dea7e8c41 (master = as of 2024-01-04), you get: In file included from /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/vector:62, from testcase.cpp:5: In static member function 'static void std::__copy_move::__assign_one(_Tp*, _Up*) [with _Tp =3D un= signed char; _Up =3D const unsigned char]', inlined from 'static _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp =3D = const unsigned char; _Up =3D unsigned char; bool _IsMove =3D false]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:441:20, inlined from '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove= =3D false; _II =3D const unsigned char*; _OI =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:507:30, inlined from '_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove= =3D false; _II =3D const unsigned char*; _OI =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:534:42, inlined from '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = =3D false; _II =3D __gnu_cxx::__normal_iterator >; _OI =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:541:31, inlined from '_OI std::copy(_II, _II, _OI) [with _II =3D __gnu_cxx::__normal_iterator >;= _OI =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:637:7, inlined from 'static _ForwardIterator std::__uninitialized_copy::__uninit_copy(_InputIterator, _InputIterat= or, _ForwardIterator) [with _InputIterator =3D __gnu_cxx::__normal_iterator >; _ForwardIterator =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_uninitia= lized.h:147:27, inlined from '_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator =3D __gnu_cxx::__normal_iterator >; _ForwardIterator =3D unsigned char*]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_uninitia= lized.h:185:15, inlined from '_ForwardIterator std::__uninitialized_copy_a(_InputIterat= or, _InputIterator, _ForwardIterator, allocator<_Tp>&) [with _InputIterator =3D __gnu_cxx::__normal_iterator >; _ForwardIterator =3D unsigned char*; _Tp =3D unsigned char]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_uninitia= lized.h:373:37, inlined from 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp =3D unsigned char; _Alloc =3D std::allocator]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_vector.h= :603:31, inlined from 'frame_t::frame_t(const frame_t&)' at testcase.cpp:7:8, inlined from 'virtual frame_t frame_filter_t::get()' at testcase.cpp:25= :14: /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_algobase= .h:399:17: warning: array subscript 0 is outside array bounds of 'unsigned char [0]' [-Warray-bounds=3D] 399 | { *__to =3D *__from; } | ~~~~~~^~~~~~~~~ In file included from /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/x86_64-pc-linux-g= nu/bits/c++allocator.h:33, from /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/allocator.h:= 46, from /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/vector:63: In member function '_Tp* std::__new_allocator<_Tp>::allocate(size_type, con= st void*) [with _Tp =3D unsigned char]', inlined from 'static _Tp* std::allocator_traits >::allocate(allocator_type&, size_type) [with _Tp =3D unsigned char]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/alloc_traits= .h:475:28, inlined from 'std::_Vector_base<_Tp, _Alloc>::pointer std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp =3D unsi= gned char; _Alloc =3D std::allocator]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_vector.h= :377:33, inlined from 'void std::_Vector_base<_Tp, _Alloc>::_M_create_storage(std::size_t) [with _Tp =3D unsigned char; _Alloc= =3D std::allocator]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_vector.h= :395:44, inlined from 'std::_Vector_base<_Tp, _Alloc>::_Vector_base(std::size_t, const allocator_type&) [with _Tp =3D unsigned char; _Alloc =3D std::allocator]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_vector.h= :331:26, inlined from 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp =3D unsigned char; _Alloc =3D std::allocator]' at /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/stl_vector.h= :600:61, inlined from 'frame_t::frame_t(const frame_t&)' at testcase.cpp:7:8, inlined from 'virtual frame_t frame_filter_t::get()' at testcase.cpp:25= :14: /home/dim/ins/gcc-14-6924-g00dea7e8c41/include/c++/14.0.0/bits/new_allocato= r.h:151:55: note: object of size 0 allocated by 'operator new' 151 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp))); | ^ I think these warnings might be bogus, since it seems to be complaining abo= ut copying an empty std::vector here? It might also get confused due to the padding inserted between the frame_t::pts_ and frame_t::timescale_ members, since if you remove either of these members, the warning goes away.=