[Bug libstdc++/67617] Non-standard const requirements imposed on associative container comparison objects

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> Both Clang/libc++ and MSVC/Dinkumware reject it for the same reason.

I notice that the Dinkumware version associated with Visual Studio 2015 accepts
the code.