On Fri, 19 Apr 2002, Andrew Brown wrote:

> >I've been trying to update a pkgsrc module and I've run into a situation
> >where the best way to enable an option seems to be to optionally patch
> >the source before building, using a specific patch selected from a set
> >of multiple optional patches (included in say ${FILESDIR}), based on
> >some setting in mk/bsd.prefs.mk and/or /etc/mk.conf.
>
> make your patch contain all features, and then enable each feature
> based on the presence of some preprocessor token.  ie, if you have a
> patch that does something for alpha machines, your patch would contain
> code surrounded by #ifdef alpha/#endif.

If that's not flexible enough, just invent tokens and switch them on
conditionally in the top level "Makefile", after ".include
../../mk/bsd.prefs.mk". Look at the output of `make -V
MACHINE_PLATFORM -V MACHINE_GNU_PLATFORM' to see what hooks you'll
have available, also popular: OBJECT_FMT and USE_INET6.

This has the advantage, for the author, that it won't trigger unwanted
behavior in some other "alpha:. In fact, it clearly has no effect
unless deliberately switched on.

Frederick