[patch] rename local _C2 identifiers in stl map header files

[Olivier Hainque]

Hello Jonathan,

> On 09 Jan 2020, at 14:26, Jonathan Wakely <jwakely@redhat.com> wrote:
> 
> Any conflict with OS headers is treated as a libstdc++ bug. We don't
> own the entire implementation namespace, so we have to play nice and
> avoid OS names.

> We maintain a list of identifiers to avoid, but _C2 is currently
> missing. Could you please add it to the coding_style.bad_identifiers
> section in doc/xml/manual/appendix_contributing.xml so we know not to
> reintroduce _C2 in future? Thanks.

Sure. Thanks for explaining. This enlightens a lot for me :)

>> Fixing the OS headers is a major hassle on VxWorks, however,
>> especially with more recent versions of the system, so we arranged
>> not to rely on it at all up to now and a straightforward adjustment
>> in the libstdc++ headers offers a way smoother and simpler way
>> forward.
>> 
>> I'm not sure what "C2" was intended to refer to so I picked
> 
> It's the Comparison function for the container. Please use _Cmp2,
> which is consistent with the partial specialization defined at the end
> of the <bits/stl_map.h> header.

Ok,

> Yes, this is fine in principle. Please update the docs and change
> _Mt to _Cmp2 though.

Sure, will adjust, test and follow up.

Thanks a lot for your lightning fast constructive feedback.

Best Regards,

Olivier