https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108323
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2024-01-30 00:00:00 |2024-2-1
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Kinda related, the implementation of locale::combine uses _M_replace_facet
which seems to have a bug:
void
locale::_Impl::
_M_replace_facet(const _Impl* __imp, const locale::id* __idp)
{
size_t __index = __idp->_M_id();
if ((__index > (__imp->_M_facets_size - 1))
|| !__imp->_M_facets[__index])
__throw_runtime_error(__N("locale::_Impl::_M_replace_facet"));
_M_install_facet(__idp, __imp->_M_facets[__index]);
}
This only checks that a facet with the specified id is present. This is not
sufficient, because it could be a different derived type that has the same id.
e.g.
struct custom_ctype : ctype<char> { ... };
auto loc = std::locale().combine<custom_ctype>(std::locale());
This should throw std::runtime_error because has_facet<custom_ctype> is false.
For combine, _M_replace_facet should use std::has_facet as specified in the
standard. I haven't checked if that would be correct for the other uses of
_M_replace_facet.
