Re: can one build commercial applications with latest gnat and other licenses related questions...

["Ludovic Brenta" <ludovic@ludovic-brenta.org>]

Stephen Leake wrote :
> klobert <klobert@sbcglobal.net> writes:
>> What's the difference in functionality between these: (gnat,
>> gccada3.44, gccada4.1.0 ? )
>
> They nominally contain the _same_ compiler, but they are slightly
> different because of release cycles.
>
> A major difference is that some of the tools that are in GNAT GPL-2006
> are not in gcc ada; notably ASIS, and the debugger may not be
> Ada-aware (depending on exactly how your distribution is configured).
>
> Also, the GNAT public releases are more reliable (more thoroughly
> tested). That's because the gcc release cycle does _not_ wait for Ada
> compiler issues, while the GNAT public release cycle does. That may
> become less of an issue over time.
>
> I believe gcc ada 4.1.0 has the same Ada 2005 features as GNAT
> GPL-2005, but I'm not sure. gcc ada 3.4.4 has no Ada 2005 features.

What I gathered by looking at the diffs of the Ada front-end and
library between releases:

GCC 3.4 < GCC 4.0 < GNAT GPL 2005 < GCC 4.1 < GCC 4.2 < GNAT GPL 2006

IIRC, most of the changes between GNAT GPL 2005 and GCC 4.1 are in the
Ada.Containers library. Support for Ada 2005 gradually improves with
each release, and seems to be complete starting with GNAT GPL 2006; at
least that's what AdaCore's marketing leads me to believe. I don't know
where each GNAT Pro release fits in that sequence.

Contrast this with the versions of the back-ends, which affect the
quality of the optimiser:

GCC 3.4.0 < GNAT GPL 2005 (3.4.4 + patches) < GNAT GPL 2006 (3.4.6) <
GCC 4.0 < GCC 4.1 < GCC 4.2

GCC 4.2 is not released yet; it is in stage 3: only bug fixes and no
more new features.

The reason why GNAT GPL is still based on GCC 3.4.x is because GCC 4.0
introduced Tree-SSA, a major change in the internal architecture of the
compiler, which has brought some instability (read: bug boxes). GCC 4.1
corrects most if not all of that instability.

-- 
Ludovic Brenta.