https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114615
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
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Keywords| |diagnostic
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Or jump threading is splitting the code into two branches for N <= 1 and N >=
2, and then warning that the N >= 2 case would read past the end of the source
buffer. But that case never actually happens.
The constructor calls _M_construct which goes to:
static void
_S_copy(_CharT* __d, const _CharT* __s, size_type __n)
{
if (__n == 1)
traits_type::assign(*__d, *__s);
else
traits_type::copy(__d, __s, __n);
}
The N == 1 case is handled here, then char_traits<wchar_t>::copy does:
static _GLIBCXX20_CONSTEXPR char_type*
copy(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
#if __cplusplus >= 202002L
if (std::__is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::copy(__s1, __s2, __n);
#endif
return wmemcpy(__s1, __s2, __n);
}
So the N == 0 case is also handled here, so we only use wmemcpy for N >= 2. And
that would indeed read N * sizeof(wchar_t), i.e. 4 or more bytes, from L""
which is only 2 bytes.
But it's unreachable, because we take the if (__n == 0) branch.
