Re: RFA: osabi: correct test for compatible handlers

[Andrew Cagney <ac131313 at redhat dot com>]

> Andrew Cagney <ac131313@redhat.com> writes:
>
>
> > > +   /* BFD's 'A->compatible (A, B)' functions return zero if A and B are
> > > +      incompatible.  But if they are compatible, it returns the 'more
> > > +      featureful' of the two arches.  That is, if A can run code
> > > +      written for B, but B can't run code written for A, then it'll
> > > +      return A.
> > > + +      struct bfd_arch_info objects are atoms: that is, there's
> > > supposed
> > > +      to be exactly one instance for a given machine.  So you can tell
> > > +      whether two are equivalent by comparing pointers.  */
> > > +   return (a == b || a->compatible (a, b) == a);
>
> > Hey, nice.
> >
> > Don't worry about a can_run_code_for function though, having the logic
> > inline makes what's happening easier to understand (and will simplify
> > a follow-on wild-card patch I've got pending).
>
>
> It may be easier for you, but the original author did get the test
> backwards, and I had to go through an embarrassing number of wrong
> tries before I got it right.  I'd really like to leave the function
> separate.

I had to go through an equally enbarrassing number of tries before I 
established exactly what the patch was doing.  Changing:

	if (compatible == handler->arch_info)

to:

	if (compatible == arch_info)

(correct?)  The really important thing here is your commentary as that 
explains exactly what is going on.  Having it as close as possible to 
the problem (the call site) is, I think, going to make things easier to 
understand.

Andrew