libstdc++/9828: Regression: Segmentation fault in num_put::put

[Benjamin Kosnik]

>__locale_cache<num_put<char> >& __lc = use_cache<num_put<char> >

Like this.

>I would think that either way, at some point the size of the cache has
>to be fixed.  Wouldn't it affect the ABI?

Maybe. I'm unsure. If it doesn't have to be exported, then size won't matter.

>Or are you thinking that the issue is that caches for different facets
>can be added later?

This. Would be nice, don't you think?

-benjamin