On 5/19/26 2:43 PM, Rainer Orth wrote:
On 5/19/26 2:06 PM, Rainer Orth wrote: ...allows the build to continue, but it still fails later: prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:432:56: error: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' accessing 18446744073709551609 or more bytes at offsets 0 and 0 overlaps 9223372036854775795 bytes at offset -9223372036854775802 [-Werror=restrict] 432 | return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));What were the previous messages? Other similar complaints have something to do with rounding up numbers that could roll over to 0x800..000 and then be passed to a library function.the full message was In file included from /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/string:45, from /vol/gcc/src/hg/master/local/gcc/rust/rust-system.h:34, from /vol/gcc/src/hg/master/local/gcc/rust/lex/rust-token.cc:19: In static member function 'static constexpr std::char_traits<char>::char_type* std::char_traits<char>::copy(char_type*, const char_type*, std::size_t)', inlined from 'static constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:487:21, inlined from 'static constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:482:7, inlined from 'constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_mutate(size_type, size_type, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.tcc:403:15, inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_append(const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.tcc:496:17, inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::append(const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:1624:18, inlined from 'constexpr _Str std::__str_concat(const typename _Str::value_type*, typename _Str::size_type, const typename _Str::value_type*, typename _Str::size_type, const typename _Str::allocator_type&) [with _Str = __cxx11::basic_string<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:3908:19, inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char; _Traits = char_traits<char>; _Alloc = allocator<char>]' at /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:3984:31, inlined from 'std::string Rust::Token::as_string() const' at /vol/gcc/src/hg/master/local/gcc/rust/lex/rust-token.cc:251:45: /var/gcc/regression/master/6.17.13-gcc-gas-gld/build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:432:56: error: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' accessing 1844674407370955118446744073709551609609 or more bytes at offsets 0 and 0 overlaps 9223372036854775795 bytes at offset -9223372036854775802 [-Werror=restrict] 432 | return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n)); Rainer
/vol/gcc/src/hg/master/local/gcc/rust/lex/rust-token.cc ... get_str () + get_type_hint_str (); _M_mutate is at bits/basic_string.tcc:392. The compiler thinks _M_mutate at 403 might ask to memcpy more than is allowed, a 40-digit number of which hex of just the first 20 digits is 0xFFFF'FFFF'FFFF'Fe50, or -432, and the rest looks random. The other numbers resolve to -0x7FFF'FFFF'FFF3' and 0x7FFF'FFFF'FFFa. I don't know what "offsets 0 and 0" might refer to. What it ought to mean is a mystery. Anyway the patch didn't change any of this. The new function _M_create_plus does the same job as the old _M_create in the same way, but might yield a little bit of extra storage that anyway would not be touched yet. Earlier versions of this patch evoked a somewhat similar complaint about allocate_at_least potentially asking __builtin_malloc for more than 0x7fff'ffff'ffff'ffff bytes, resolved by subtracting 1 if rounding-up ever actually got there. The caller of _M_mutate has already verified the value passed to its argument __len2 is within bounds. Lower-level code multiplies the value by sizeof(_CharT), but it has been capped such that the product is not too large. The 40-digit number looks like a compiler bug. Nathan
