[Bug libstdc++/103340] [12 Regression] constexpr std::string is incompatible with --enable-libstdcxx-allocator

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103340

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #0)
> Only __gnu_cxx::new_allocator is usable in constant expressions.

And __gnu_cxx::malloc_allocator.

Making the others work isn't difficult.