Why C++ compiles slowly

[Walter Bright]

Steven Schveighoffer wrote:
> Better, now takes 20 seconds vs over 60.  The new culprit:
> 
> Flat profile:
> 
> Each sample counts as 0.01 seconds.
>   %   cumulative   self              self     total
>  time   seconds   seconds    calls  ms/call  ms/call  name
>  75.79      6.51     6.51     8103     0.80     0.80  
> TemplateDeclaration::toJsonBuffer(OutBuffer*)

This is most peculiar, as that should have shown up on the previous profile.

> I haven't looked at toJsonBuffer at all (btw, why are we calling this 
> function if I'm not outputting json?)

That only happens if -X is passed on the command line, or one of the files on 
the command line has a .json index.