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* [Bug c++/54924] New: Warn for std::string constructor with wrong size @ 2012-10-14 17:06 david at doublewise dot net 2012-10-14 17:44 ` [Bug libstdc++/54924] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: david at doublewise dot net @ 2012-10-14 17:06 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54924 Bug #: 54924 Summary: Warn for std::string constructor with wrong size Classification: Unclassified Product: gcc Version: 4.7.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: david@doublewise.net The constructor for std::string that takes an array of char and a size assumes that the array of char you pass in is at least as large as the size you specify. In other words, std::string str('0', 100) is undefined behavior. As I show in this example, the real issue can be much more subtle if escape characters are involved: http://stackoverflow.com/questions/164168/how-do-you-construct-a-stdstring-with-an-embedded-null/12884464#12884464 It would be nice if gcc warned when the size specified in the constructor exceeds the size of the array passed as the first argument. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/54924] Warn for std::string constructor with wrong size 2012-10-14 17:06 [Bug c++/54924] New: Warn for std::string constructor with wrong size david at doublewise dot net @ 2012-10-14 17:44 ` redi at gcc dot gnu.org 2012-10-14 18:40 ` david at doublewise dot net ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2012-10-14 17:44 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54924 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Keywords| |diagnostic Last reconfirmed| |2012-10-14 Component|c++ |libstdc++ Ever Confirmed|0 |1 Severity|normal |enhancement --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-14 17:44:17 UTC --- (In reply to comment #0) > In other words, std::string str('0', 100) is undefined behavior. I assume you mean std::string str("0", 100) We might be able to use http://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/54924] Warn for std::string constructor with wrong size 2012-10-14 17:06 [Bug c++/54924] New: Warn for std::string constructor with wrong size david at doublewise dot net 2012-10-14 17:44 ` [Bug libstdc++/54924] " redi at gcc dot gnu.org @ 2012-10-14 18:40 ` david at doublewise dot net 2021-12-15 17:58 ` msebor at gcc dot gnu.org 2021-12-15 21:30 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: david at doublewise dot net @ 2012-10-14 18:40 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54924 David Stone <david at doublewise dot net> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |david at doublewise dot net --- Comment #2 from David Stone <david at doublewise dot net> 2012-10-14 18:40:33 UTC --- Yeah, sorry, I meant the (char const *, size_t) overload, not the (size_t, char) overload. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/54924] Warn for std::string constructor with wrong size 2012-10-14 17:06 [Bug c++/54924] New: Warn for std::string constructor with wrong size david at doublewise dot net 2012-10-14 17:44 ` [Bug libstdc++/54924] " redi at gcc dot gnu.org 2012-10-14 18:40 ` david at doublewise dot net @ 2021-12-15 17:58 ` msebor at gcc dot gnu.org 2021-12-15 21:30 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: msebor at gcc dot gnu.org @ 2021-12-15 17:58 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54924 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|ASSIGNED |RESOLVED --- Comment #15 from Martin Sebor <msebor at gcc dot gnu.org> --- GCC 11 and 12 finally diagnose this problem even without -Wsystem-headers, albeit inconsistently. At -O1 GCC 11 issues -Wstringop-overread: In file included from /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/string:40, from pr54924.C:2: In static member function ‘static std::char_traits<char>::char_type* std::char_traits<char>::copy(std::char_traits<char>::char_type*, const char_type*, std::size_t)’, inlined from ‘static void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:359:21, inlined from ‘static void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy_chars(_CharT*, const _CharT*, const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:406:16, inlined from ‘void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_construct(_InIterator, _InIterator, std::forward_iterator_tag) [with _FwdIterator = const char*; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.tcc:225:25, inlined from ‘void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_construct_aux(_InIterator, _InIterator, std::__false_type) [with _InIterator = const char*; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:255:23, inlined from ‘void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_construct(_InIterator, _InIterator) [with _InIterator = const char*; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:274:20, inlined from ‘std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:521:21, inlined from ‘void __static_initialization_and_destruction_0(int, int)’ at pr54924.C:4:24, inlined from ‘(static initializers for pr54924.C)’ at pr54924.C:4:25: /build/gcc-11-branch/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:409:56: warning: ‘void* __builtin_memcpy(void*, const void*, long unsigned int)’ reading 5 bytes from a region of size 4 [-Wstringop-overread] 409 | return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n)); | ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~ As a result of g:b8f2efaed02e8b03d215d74e42d3707761772f64 GCC 12 doesn't issue -Wstringop-overread at any level but at -O2 it does issue -Warray-bounds: In file included from /build/gcc-master/x86_64-pc-linux-gnu/libstdc++-v3/include/string:53, from pr54924.C:2: In constructor ‘std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’, inlined from ‘void __static_initialization_and_destruction_0(int, int)’ at pr54924.C:4:24, inlined from ‘(static initializers for pr54924.C)’ at pr54924.C:4:25: /build/gcc-master/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:620:21: warning: array subscript 5 is outside array bounds of ‘const char [4]’ [-Warray-bounds] 620 | _M_construct(__s, __s + __n, std::forward_iterator_tag()); | ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'm not happy with how this has turned out but I'm also not sure how to improve things, so I'll resolve this as fixed. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/54924] Warn for std::string constructor with wrong size 2012-10-14 17:06 [Bug c++/54924] New: Warn for std::string constructor with wrong size david at doublewise dot net ` (2 preceding siblings ...) 2021-12-15 17:58 ` msebor at gcc dot gnu.org @ 2021-12-15 21:30 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2021-12-15 21:30 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54924 --- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #14) > Created attachment 43350 [details] > Patch to use __builtin_object_size in std::string > > So it isn't lost, here's a prototype I was working on last year (which only > helps if you use -Wsystem-headers). Huh, I forgot about this patch and then reinvented that wheel: https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581376.html ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-12-15 21:30 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-10-14 17:06 [Bug c++/54924] New: Warn for std::string constructor with wrong size david at doublewise dot net 2012-10-14 17:44 ` [Bug libstdc++/54924] " redi at gcc dot gnu.org 2012-10-14 18:40 ` david at doublewise dot net 2021-12-15 17:58 ` msebor at gcc dot gnu.org 2021-12-15 21:30 ` redi at gcc dot gnu.org
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