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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Possible compiler bug with this simple program
Date: Wed, 3 Sep 2008 22:53:45 -0500
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Xref: g2news2.google.com comp.lang.ada:7632
Date: 2008-09-03T22:53:45-05:00
List-Id: <comp.lang.ada>

"Adam Beneschan" <adam@irvine.com> wrote in message 
news:90006a35-e933-40f1-9a76-5698b0ce75d1@s20g2000prd.googlegroups.com...
...
>> The difference between the two cases ([1] described above, herein, and
>> [2] the code in mixed Ada and C that I posted earlier), is that in
>> [1], both the called procedure and the callback procedure are written
>> in C, and the in problematic code [2], the called subprogram is in C
>> (plmap) but the callback (mapform19) is written in Ada, with C
>> conventions.
>
> Yup, this is not surprising at all to me.  And if you go back and
> reread my earlier post, I believe I explained pretty thoroughly why
> this is happening, and also gave you a solution.  Don't use an
> unconstrained array type in your callback routine.  Period.  You can
> use unconstrained arrays when calling C routines from Ada; but if
> you're going to call Ada routines from C, don't.

Right. It is *only* OK to use an unconstrained array parameter in a 
subprogram that has pragma Import. It is *not* OK in any other context for C 
(objects, subprograms with Convention or Export pragmas, function returns of 
any kind). Your program is still using pragma Convention and you are still 
having C call Ada with an unconstrained parameter. You can't do that 
portably.

I may have not looked carefully enough at your original program; I presumed 
that reason you were using pragma Convention was so that you could write the 
routine in Ada, and that it would be replaced by pragma Import in the real 
program. If that was wrong, I probably mislead you.

                                              Randy.