Re: OR_AND semantics (was: GNU property saga)

[Jim Dehnert <dehnert at gmail dot com>]

On Thu, Mar 7, 2019 at 10:06 PM Cary Coutant <ccoutant@gmail.com> wrote:

> > > Now the above language would include FEATURE_X in the output, but bit 4
> > > would be reliable (set a.bit4 && b.bit4) while bit 5 would be
> unreliable
> > > (it is zero, even if it is one in a.o and _would_ be one in b.o had we
> > > used a newer producer).
> >
> > We can't add a bit to FEATURE_X in such a way that  FEATURE_X generated
> > by older producers become invalid.   We must add the bit to FEATURE_Y
> which is
> > unsupported to all prior producers.  Am I missing something obvious?
>
> Yes, I think so. This is the point Michael (and I) were making. By
> using KNOWN bits, you can add new feature bits without having to start
> a whole new word of bits.
>

You also don't need to assume that a producer that has implemented support
for the tenth feature bit is also generating valid values for the
previously-defined nine, just because the words containing them are present.

Jim

>
> -cary
>
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-- 
--
             Jim Dehnert
             dehnert@gmail.com