Re: Crosspost: Help wanted from comp.compilers

["Robert I. Eachus" <rieachus@attbi.com>]

Larry Kilgallen wrote:

> That seems to me a very impolite non-answer.
> 
> Even if one granted the obligation of every person to be a full expert
> in every issue on which they commented, this is a newsgroup that many
> others are reading, not an email discussion.

It seemed extremely polite to me.  There have been two things going on 
here.  An informative discussion of Ada recompilation policies and why 
they are the way they are, and Hyman Rosen continually jumping in to 
pour more gasoline on the flames.  There is a lot I can add to the 
intelligent discussion but I try to control my input to avoid feeding 
the troll.

For example, there were cases where Verdix 5.4.1? blew link-time 
dependences invovling generic instantiations and required creating a new 
library and recompiling the world.  A bug?  Sure.  But the bug was there 
because Verdix did a much better job of mananging generic instances and 
their dependences, then got confused by some second order effect when 
generic unit bodies were modified.  The usual failure was a generic A 
withed generic B, and package C contained an instance of A.  Recompiling 
the body of A did not invalidate the compile of C--it only depended on 
the spec.  But that change to the body of A could create a need for new 
instances of B.  If there was a naming conflict between the new 
instances of B (in the body of A) and the old, Verdix basically threw up 
its hands.  Recompiling everything got rid of the conflicts.

So why use Verdix?  Because the elimination of the permitted (by the RM) 
but not required dependences meant that you could do things with Verdix 
that were not possible with other Ada compilers.

-- 

                                                        Robert I. Eachus

�In an ally, considerations of house, clan, planet, race are 
insignificant beside two prime questions, which are: 1. Can he shoot? 2. 
Will he aim at your enemy?� -- from the Laiden novels by Sharon Lee and 
Steve Miller.