https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113099
--- Comment #12 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to andysem from comment #11)
> > I'm not sure what you mean by "the compiler is free to generate code that
> > takes it into account." Takes what into account? What problem does that
> > freedom cause?
>
> I mean the compiler could move (some part of) dynamic_cast to precede the
> check for the standard facet. I.e. of something like this:
>
> template< typename _Facet >
> const _Facet* __try_use_facet(locale const& loc)
> {
> const size_t __i = _Facet::id._M_id();
> const locale::facet** __facets = __loc._M_impl->_M_facets;
> const _Facet* __dyn_facet = __dynamic_cast< const _Facet*
> >(__facets[__i]);
>
> // checks for every standard facet type
> if (__is_same(_Facet, ...))
> return static_cast<const _Facet*>(__facets[__i]);
>
> return __dyn_facet;
> }
But why? Maybe I'm being slow but I still don't understand what problem is
being solved here.
Also this would defeat the optimization that avoids the unnecessary overhead of
dynamic_cast for standard facets.
> AFAIK, the standard or libstdc++ docs do not require RTTI for std::locale to
> function.
The standard requires RTTI, period. Using -fno-rtti is completely non-standard
and so the standard has nothing to say about it.
