Multilibs - how to avoid building the default one twice

[Ian Lance Taylor]

"Zack Weinberg" <zack@codesourcery.com> writes:

> > MULTILIB_DEFAULTS should convey this information.
> 
> ... which is supposed to be defined in tm.h, unlike all the other
> MULTILIB_ thingies that go in the makefile fragment.  How ... sensible.

I did it that way because there were a bunch of targets which had
different defaults but didn't have different makefile fragments.

Typically a single makefile fragment would work for all the CPU
variants.  E.g., config/m68k/t-m68kbare, the canonical example when I
was hacking on multilibs.  But as you can see in
config/m68k/m68k-none.h, there are different versions of
MULTILIB_DEFAULTS which are controlled by TARGET_DEFAULT.  If
MULTILIB_DEFAULTS were to go into the makefile fragment, we would have
to duplicate makefile fragments purely to set the defaults.

My recollection is that all the multilib variables used to be
documented in the same place, at least.  I see that that is no longer
the case.

Ian