On 5/19/26 7:19 PM, Nathan Myers wrote:
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
[Looking back at the original report, the 40-digit number must
be a cut and paste error. So...]
/vol/gcc/src/hg/master/local/gcc/rust/lex/rust-token.cc
... get_str () + get_type_hint_str ();
... reaches vector<>::_M_mutate
> defined at bits/basic_string.tcc:392. The compiler> thinks _M_mutate
at 403,
this->_S_copy(__r.__ptr + __pos, __s, __len2);
(with __r.__ptr + __pos pointing immediately past
bytes from get_str()'s result as copied to freshly
allocated memory, and __s and __len2 the contents of
get_type_hint_str()'s result)
might try to ask memcpy to copy more than is allowed,
to wit, 18446744073709551609, or -7ull.
The other numbers resolve to -0x7FFF'FFFF'FFF3'
and 0x7FFF'FFFF'FFFa. I don't know what "offsets 0 and 0"
might refer to.
Is it saying it thinks the memcpy might be copying
overlapping ranges?
... 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.
