https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109909
Bug ID: 109909 Summary: vector<uchar>: Writing 8 bytes into 1 allocated byte Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: terra at gnome dot org Target Milestone: --- Created attachment 55119 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55119&action=edit Preprocessed source code The following piece of code, when compiled, shows a warning about writing 8 bytes into an address for which 1 byte was allocated. Tentatively blaming the compiler although it might just as well be a library issue. Severity could be anything from fairly trivial ("just a bogus warning") to really bad ("overwriting memory it should not"). Both "-std=gnu++20" and "-O3" seem to be required to trigger the warning. $ cat ttt.C #include <vector> struct Oink { using utype = unsigned char;// in gcc13 this triggers // /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_construct.h:97:14: warning: writing 8 bytes into a region of size 1 [-Wstringop-overflow=] // using the next line does not. // using utype = long long; utype mValue = 0; }; std::vector<Oink> mSty; void foo() { mSty.resize(1); } $ /usr/local/products/gcc/13.1.0/bin/g++ -std=gnu++20 -c -v -O3 ttt.C Using built-in specs. COLLECT_GCC=/usr/local/products/gcc/13.1.0/bin/g++ Target: x86_64-suse-linux Configured with: ../../gcc-13.1.0/configure --enable-languages=c,c++,fortran --enable-targets=x86_64-suse-linux,i686-suse-linux --prefix=/usr/local/products/gcc/13.1.0 --with-gnu-as --with-as=/usr/local/products/gcc/binutils-2.40/bin/as --with-ld=/usr/local/products/gcc/binutils-2.40/bin/ld.gold --enable-link-mutex --enable-gnu-indirect-functions --enable-linux-futex --enable-threads=posix --enable-shared --enable-__cxa_atexit --enable-libstdcxx-allocator=new x86_64-suse-linux Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 13.1.0 (GCC) COLLECT_GCC_OPTIONS='-std=gnu++20' '-c' '-v' '-O3' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/local/products/gcc/13.1.0/lib/gcc/x86_64-suse-linux/13.1.0/cc1plus -quiet -v -D_GNU_SOURCE ttt.C -quiet -dumpbase ttt.C -dumpbase-ext .C -mtune=generic -march=x86-64 -O3 -std=gnu++20 -version -o /tmp/ccxuQqee.s GNU C++20 (GCC) version 13.1.0 (x86_64-suse-linux) compiled by GNU C version 13.1.0, GMP version 6.2.1, MPFR version 4.2.0, MPC version 1.3.1, isl version isl-0.18-GMP GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 ignoring nonexistent directory "/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../../x86_64-suse-linux/include" #include "..." search starts here: #include <...> search starts here: /usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../../include/c++/13.1.0 /usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../../include/c++/13.1.0/x86_64-suse-linux /usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../../include/c++/13.1.0/backward /usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/include /usr/local/include /usr/local/products/gcc/13.1.0/include /usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/include-fixed /usr/include End of search list. Compiler executable checksum: 759d8432ee23c1bd4b520a57099ed580 In file included from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_iterator.h:85, from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_algobase.h:67, from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/vector:62, from ttt.C:1: In function ‘constexpr decltype (::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...) [with _Tp = Oink; _Args = {Oink}]’, inlined from ‘static constexpr void std::allocator_traits<std::allocator<_Up> >::construct(allocator_type&, _Up*, _Args&& ...) [with _Up = Oink; _Args = {Oink}; _Tp = Oink]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/alloc_traits.h:539:21, inlined from ‘constexpr void std::__relocate_object_a(_Tp*, _Up*, _Allocator&) [with _Tp = Oink; _Up = Oink; _Allocator = allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_uninitialized.h:1072:26, inlined from ‘constexpr _ForwardIterator std::__relocate_a_1(_InputIterator, _InputIterator, _ForwardIterator, _Allocator&) [with _InputIterator = Oink*; _ForwardIterator = Oink*; _Allocator = allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_uninitialized.h:1100:26, inlined from ‘constexpr _ForwardIterator std::__relocate_a(_InputIterator, _InputIterator, _ForwardIterator, _Allocator&) [with _InputIterator = Oink*; _ForwardIterator = Oink*; _Allocator = allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_uninitialized.h:1142:33, inlined from ‘static constexpr std::vector<_Tp, _Alloc>::pointer std::vector<_Tp, _Alloc>::_S_relocate(pointer, pointer, pointer, _Tp_alloc_type&) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_vector.h:504:26, inlined from ‘constexpr void std::vector<_Tp, _Alloc>::_M_default_append(size_type) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/vector.tcc:676:16, inlined from ‘constexpr void std::vector<_Tp, _Alloc>::resize(size_type) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_vector.h:1011:21, inlined from ‘void foo()’ at ttt.C:15:14: /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_construct.h:97:14: warning: writing 8 bytes into a region of size 1 [-Wstringop-overflow=] 97 | { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); } | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/x86_64-suse-linux/bits/c++allocator.h:33, from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/allocator.h:46, from /usr/local/products/gcc/13.1.0/include/c++/13.1.0/vector:63: In member function ‘_Tp* std::__new_allocator<_Tp>::allocate(size_type, const void*) [with _Tp = Oink]’, inlined from ‘constexpr _Tp* std::allocator< <template-parameter-1-1> >::allocate(std::size_t) [with _Tp = Oink]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/allocator.h:198:40, inlined from ‘static constexpr _Tp* std::allocator_traits<std::allocator<_Up> >::allocate(allocator_type&, size_type) [with _Tp = Oink]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/alloc_traits.h:482:28, inlined from ‘constexpr std::_Vector_base<_Tp, _Alloc>::pointer std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_vector.h:378:33, inlined from ‘constexpr void std::vector<_Tp, _Alloc>::_M_default_append(size_type) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/vector.tcc:663:45, inlined from ‘constexpr void std::vector<_Tp, _Alloc>::resize(size_type) [with _Tp = Oink; _Alloc = std::allocator<Oink>]’ at /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/stl_vector.h:1011:21, inlined from ‘void foo()’ at ttt.C:15:14: /usr/local/products/gcc/13.1.0/include/c++/13.1.0/bits/new_allocator.h:147:55: note: destination object of size 1 allocated by ‘operator new’ 147 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp))); | ^ COLLECT_GCC_OPTIONS='-std=gnu++20' '-c' '-v' '-O3' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/local/products/gcc/binutils-2.40/bin/as -v --64 -o ttt.o /tmp/ccxuQqee.s GNU assembler version 2.40 (x86_64-suse-linux) using BFD version (GNU Binutils) 2.40 COMPILER_PATH=/usr/local/products/gcc/13.1.0/lib/gcc/x86_64-suse-linux/13.1.0/:/usr/local/products/gcc/13.1.0/lib/gcc/x86_64-suse-linux/13.1.0/:/usr/local/products/gcc/13.1.0/lib/gcc/x86_64-suse-linux/:/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/:/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/ LIBRARY_PATH=/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/:/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/local/products/gcc/13.1.0/lib64/gcc/x86_64-suse-linux/13.1.0/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS='-std=gnu++20' '-c' '-v' '-O3' '-shared-libgcc' '-mtune=generic' '-march=x86-64'