Re: ADA compilers/ difference between 83 and 95

Re: ADA compilers/ difference between 83 and 95

[Chris Albertson]

--- Patty <patricia.l.addiss@honeywell.com> wrote:

> Yes, we are trying to port an existing application.  I have looked at
> GNAT, but they only have ADA95.
> 
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada-france.org
> http://www.ada-france.org/mailman/listinfo/comp.lang.ada
> 


Chris Albertson
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Re: ADA compilers/ difference between 83 and 95

[Chris Albertson]

Sorry aout the last message hadno text. Here is is again


I'm curious, will ada83 programs not compile under ada95?

If there is a problem where is it?  What part of the language spec
changed in an incompatable way?  Yes I do have some old code that
currently runs on a VAX and I'm like to get it running on a
Duel Xeon system under Solaris 10.  I assumed only minor work 
would be required.  I think gnat has a switch to disallow
the '95 syntax.  

I would not want to use an old compiler, so much work has been
done in recent years it would be a shame not to take advantage
of it



Chris Albertson
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org
  KG6OMK

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Re: ADA compilers/ difference between 83 and 95

[Keith Thompson]

Chris Albertson <chrisalbertson90278@yahoo.com> writes:
> Sorry aout the last message hadno text. Here is is again
>
> I'm curious, will ada83 programs not compile under ada95?
>
> If there is a problem where is it?  What part of the language spec
> changed in an incompatable way?
[snip]

The biggest change is the new reserved words that Ada 83 programs
might use as identifiers.  (That's actually not a very common problem,
as far as I know).

The best way to find out is to try compiling the code with an Ada 95
compiler and read the error messages.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.

Re: ADA compilers/ difference between 83 and 95 - The answer

[Jeff C]

Chris Albertson wrote:
> Sorry aout the last message hadno text. Here is is again
> 
> 
> I'm curious, will ada83 programs not compile under ada95?
> 

Some programs or packages from Ada 83 will indeed not compile but again 
it is generally no more of a problem than switching compiler vendors.

See this link:

http://www.adaic.org/learn/tech/8395comp.html

Summary. Along with my experience

a) A few new reserved words. (Never ran into this one)
b) New form required for indefinitite generic parameters (I hit this once)
c) Packages can not  have a body if their spec does not require it (I 
hit this once. It was always a bad idea by the way_
d) Character now has 256 items instead of 128 (never hurt by this one)
e) Numeric_Error no longer unique. Now renames of constraint error 
(Never hurt by this one)

That is all the site listed. I believe I ran into an additional problem 
with an attribute that was renamed/removed on floats ('small?) which is 
not listed on that link.

Other issues you will run into (that will happen regardless of the Ada 
83 v.s. Ada 95 thing)

1) Use of vendor supplied packagages - Can be a big deal.
2) Use of vendor specific attributes or pragmas  - can be a moderate deal
3) Different level of support for rep-specs - can be a big deal
4) Different approach for supporting package Machine_Code insertions
5) Code that relies on buggy behavior of the old compiler

Re: ADA compilers/ difference between 83 and 95

[Jeffrey Carter]

Chris Albertson wrote:

> If there is a problem where is it?  What part of the language spec
> changed in an incompatable way?  Yes I do have some old code that
> currently runs on a VAX and I'm like to get it running on a
> Duel Xeon system under Solaris 10.  I assumed only minor work 
> would be required.  I think gnat has a switch to disallow
> the '95 syntax.  

I've compiled lots of Ada-83 code with Ada-95 compilers and never had a 
serious problem. The important thing is that the code was designed to be 
portable in the first place. If you have lots of compiler or platform 
dependencies in your code, it becomes harder.

-- 
Jeff Carter
"Oh Lord, bless this thy hand grenade, that with it thou
mayst blow thine enemies to tiny bits, in thy mercy."
Monty Python and the Holy Grail
24

Re: ADA compilers/ difference between 83 and 95 - The answer

[Pascal Obry]

Jeff C <jcreem@yahoo.com> writes:

> Summary. Along with my experience
> 
> a) A few new reserved words. (Never ran into this one)

Trivial to fix and safe.

> b) New form required for indefinitite generic parameters (I hit this once)

Trivial to fix and safe.

> c) Packages can not  have a body if their spec does not require it (I hit
> this once. It was always a bad idea by the way_

Trivial to fix and safe. Just add Pragma Elaborate_Body in the spec.

> d) Character now has 256 items instead of 128 (never hurt by this one)

Easy to fix but requires some code review.

> e) Numeric_Error no longer unique. Now renames of constraint error (Never
>    hurt by this one)

Easy to fix but requires some code review.

So as you see going from Ada83 to Ada95 is not that difficult. This was the
design decision when designing Ada95: It must be upward compatible. And in
practice it is.

Pascal.

-- 

--|------------------------------------------------------
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Re: ADA compilers/ difference between 83 and 95

[Marin David Condic]

I've ported a LOT of VAX/VMS (DEC) Ada 83 to Gnat Ada95 and never 
encountered anything that was a problem between the two language 
versions. There may be some obscure corner-case rules that trigger 
incompatibilities but in practical use, I just never encountered any. I 
did get some warnings about using the package ASCII and maybe that's as 
close to an incompatability as I've seen.

Mostly, I had some issues where different compiler writers had different 
views of what to implement. A few instances where DEC Ada handled 
unconstrained types differently from Gnat Ada and, of course, some 
vendor specific implementation details once in a while (like packages 
that may or may not be there because they are vendor supplied) but two 
observations: I don't recall anything that got past the compiler that 
ended up being an issue - so the compiler is your friend here. I don't 
recall anything that didn't run just fine when it finally linked. I 
*have* had problems when porting between two *different* platforms - 
mostly with byte-sex issues, but that has been minimal. (Ada 95 has some 
features to help you out making byte-sex issues portable as well, but I 
have not delved into them lately)

Porting even a large body of Ada code (if reasonably well written to be 
portable - no fair throwing in compiler-specific things in every unit & 
expecting zero effort) even across platforms has not been much of an 
issue in my experience. I've done a few hundred thousand lines in a 
couple of days & had it up and running - but it was *my* code so I was 
familiar with it and I have usually had the wisdom to isolate any 
compiler specifics. Even a stranger's code being moved across platforms 
and to a different language standard ought to be minimal fuss.

MDC


Chris Albertson wrote:
> Sorry aout the last message hadno text. Here is is again
> 
> 
> I'm curious, will ada83 programs not compile under ada95?
> 


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