Re: Overriding discriminants perplexes GNAT 3.14p

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

Dmitry A.Kazakov <mailbox@dmitry-kazakov.de> writes:

> Stephen Leake wrote:
> 
> > Dmitry A.Kazakov <mailbox@dmitry-kazakov.de> writes:
> > 
> >> People rightly criticize MS VC++, but the situation with Ada
> >> compilers isn't much better.
> > 
> > Yes it is (in my experience). I've found bugs in _every_ compiler I've
> > ever used. At least with GNAT I have a chance of getting them fixed!
> 
> First of all there are bugs and bugs. GNAT is at least ten years old, so I 
> would expect that one could not catch it on such primitive things. What you 
> are talking about is merely a quality of support, which is a very important 
> but yet another thing. Moreover, from what Robert Dewar said before his 
> departure, it looks like excellent and thus expensive support actually 
> harms quality. ACT intentionally limits the number of GNAT users by those 
> with very deep pockets and applications which do not require all stregths 
> of Ada. Should GNAT Pro be affordable for small and medium sized projects, 
> then Ada would be applied much more wider with so terrifying ACT 
> consequence of an increasing support demand.

You are making a couple of assumptions that I find dubious.

1) More and cheaper customers = higher quality

I don't believe this, because the first consequence of more cheaper
customers is to spread your support personnel thinner, so they have
less time to write quality fixes for the bugs that get reported. 

2) ACT customers do not require all strengths of Ada. 

GNAT is the only compiler to support _all_ of the Ada Annexes. ACT
only supports code that customers demand. So I have to believe that
there is at least one ACT customers using each part of Ada. Which also
helps defeat assumption 1).

> >> I judge from my experience with GNAT and Object Ada.
> > 
> > GNAT is better than Object Ada
> 
> I wouldn't say that. From my sad experience [I was forced to create a small 
> validation site] Object Ada compiles many examples which perplexe GNAT. It 
> also makes a better code. 

Ok, it is certainly true that compilers perform differently on
different types of code; I suspect your code is in a different domain
than mine.

> The major problem with Object Ada is that it sometimes hangs and
> sometimes joyfully generates nonsense, especially when it tries to
> optimize return statements with controlled types.

That's a show stopper for me :).

> > DEC was good. GNAT is better! And yes, I _did_ find bugs in the DEC
> > Ada compiler.
> 
> Lucky one (:-)). For five years GNAT was unable to compile my program in 
> Ada 83 written for DEC Ada. [I must admit, I slightly overused generics 
> there]

Yeah, I've hit a few bugs in GNAT generics as well. Fixed now :).

> Yes *now* GNAT is better than DEC Ada that time. 

That is what I meant. Certainly the first version of GNAT (3.09?) was
pretty horrible.

> Though there is nothing comparable with LSE and DEC debugger. 

Emacs and gdb (current versions) are better than LSE and DEC debugger,
but just barely.

> But what if mismanagement and "new economy" didn't kill DEC?

Then I'd be running VMS instead of Windows, and Linux would never have
gotten started (hey, I can dream, can't I :).

> > Compilers are _extremely_ complicated systems. It is _not_ possible to
> > ensure they have no bugs.
> > 
> > Please report your bug to report@gnat.com, following the instructions
> > in the GNAT BUG box. Or let me know, and I'll do it.
> 
> It is better if you do that, because you are working with 3.15. 

Hmm. I don't want to abuse my support contract by submitting bugs that
I have not encountered in my work. I'll send this one in, but from now
on I won't make that offer.

And ACT does look at bug reports from non-customers, especially if
they are simple to reproduce (as yours is).

> Here is a pair of "gems" from my collection:

Send them in to ACT; they will get fixed in a future version.

-- 
-- Stephe