It's (PCH) merging time!

[Tim Josling]

Geoff Keating wrote:
> 
> Tim Josling <tej@melbpc.org.au> writes:
> 
> > The problem is that the output of gengtype$(exe) depends on all the
> > files it scans. In particular the file gtype-desc.h has stuff from
> > potentially all the files it scans, and it is included by many
> > files. So this creates a many->many dependency. gtype-desc.h only
> > has a new change date/time if it actually gets changed.
> >
> > So, if the dependencies are set up writing, changing one of many files causes
> > many files to be recompiled.
> >
> > Maybe the solution is worse than the disease because you generate a lot of
> > recompiles that are useless but I don't know how to avoid it.
> 
> What's wrong with the current solution for this, using s-gtype?  All
> the dependencies seem to be specified correctly (other than the
> Makefile:ada/config-lang.in dependency, which would seem to be a
> long-standing bug easily fixed by changing ada/Make-lang.in).
> 
> --
> - Geoffrey Keating <geoffk@geoffk.org>

Yes, though as Fergus pointed out it is not just Ada, all the languages need a
similar deendency,

Tim Josling