Re: GNAT Opinions

[dewar@gnat.com]

In article <36910C32.1A0543E7@magic.fr>,
  Pascal MALAISE <malaise@magic.fr> wrote:

> gnat compiling policy is restrictive, and despite the
> *nice* gnatchop, it is difficult to maintain both
> versions with unique sources. It is  difficult to insert
> gnat compilation within an existing (and Verdix oriented)
> ada CASE  environment.

Actually this is fairly straightforward, but it is
definitely the sort of thing on which many users need help,
we have helped a number of our supported customers do
exactly this, and there are several succesful approaches
that can be used, depending on issues such as whether or
not preprocessing is used.


> gnat has some (specific or ada 95?) constraints on
> representation clauses which have to be defined before
> the usage of the type which forbids to
> put them in private parts.

Just to be clear here, it is fine to put rep clauses in
private parts, the prohibition is that a rep clause cannot
come after the type is frozen. The freezing rules are
actually pretty similar in Ada 83 and Ada 95.

Adapting and dealing with problematic rep clauses is
certainly one of the major support activities for us in
dealing with legacy code. In our experience, the problem is
often neither with GNAT nor with Ada 95, it is just that
the original code is plain wrong, and was erroneously
accepted by the Ada 83 compiler, or it was implementation
dependent code that depended, e.g. on a particular
implementation of the Size attribute.

Robert Dewar
Ada Core Technologies

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