[C++ Patch] More location fixes to grokdeclarator

[David Malcolm]

On Tue, 2018-06-26 at 01:44 +0200, Paolo Carlini wrote:
> Hi,
> 
> this includes straightforward tweaks to check_concept_fn and quite a
> bit 
> of additional work on grokdeclarator: most of it is also rather 
> straightforward. In a few places there is the subtlety that we want
> to 
> handle together ds_storage_class and ds_thread, whichever location
> is 
> the smallest but != UNKNOWN_LOCATION (UNKNWON_LOCATION meaning that
> the 
> issue is with the other one) or use the biggest location when say 
> ds_virtual and ds_storage_class conflict, because - I believe - we
> want 
> to point to the place where we give up. Thus I added the
> min_location 
> and max_location helpers. 

Note that directly comparing location_t values can be problematic: (one
value might be an ad-hoc location, and the other not; one might be a
macro expansion, etc).

You might want to use linemap_compare_locations or
linemap_location_before_p for this.

Hope this is helpful
Dave