Gnat Ada binary compatibility

Gnat Ada binary compatibility

[Scorpion]

Hello,

we use Dec Ada in a homogenous VMS AXP environment. Now, we want to migrate
to Gnat Ada95 first and then to Gnat Ada on Tru64 Unix (both alpha hardware
and little endian). We are using an RPC mechanism, which tranfers binary
data, represented by complex Ada variant records. Is there a chance, that we
can continue doing this between OpenVMS AXP and Tru64 AXP? Or do we have to
introduce data mashalling in any case.

best regards

Jakob

Re: Gnat Ada binary compatibility (between Alpha operating systems)

[Larry Kilgallen]

In article <3df79d5a$1@news.swissonline.ch>, "Scorpion" <erber@yahoo.de> writes:

> we use Dec Ada in a homogenous VMS AXP environment. Now, we want to migrate
> to Gnat Ada95 first and then to Gnat Ada on Tru64 Unix (both alpha hardware
> and little endian). We are using an RPC mechanism, which tranfers binary
> data, represented by complex Ada variant records. Is there a chance, that we
> can continue doing this between OpenVMS AXP and Tru64 AXP? Or do we have to
> introduce data mashalling in any case.

If you have floating point in your data, consider what floating point
types you require.  VMS supports certain types only because of VAX
heritage -- the Ada compilers on VMS may do the same.

Re: Gnat Ada binary compatibility

[Thierry Lelegard]

> we use Dec Ada in a homogenous VMS AXP environment. Now, we want to migrate
> to Gnat Ada95 first and then to Gnat Ada on Tru64 Unix (both alpha hardware
> and little endian). We are using an RPC mechanism, which tranfers binary
> data, represented by complex Ada variant records. Is there a chance, that we
> can continue doing this between OpenVMS AXP and Tru64 AXP? Or do we have to
> introduce data mashalling in any case.

We had exactly the same situation: moving to GNAT/multi-OS a DEC Ada/VMS
application which did binary transfers (without marshalling) of variant Ada
records. This approach is buggy, even in Ada83, even using DEC Ada only. It
works only by chance. More precisely, it works only if write and read buffers
(ie. the Ada variables) either are both unconstrained or have both the same
constraints. But, anyway, this is only a fortunate (?) undocumented unsupported
side effect of the compiler.

We solved that by using marshalling. This approach is correct, portable
and inter-operable. If you do not want to do the marshalling yourself,
you may use some middleware that will do this for you (CORBA or DSA,
although DSA is non-inter-operable outside GNAT).

We now use both approaches (hand-made marshalling and CORBA) successfully.
-Thierry

Re: Gnat Ada binary compatibility

[Jean-Claude Mahieux]

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Jakob,

in case you wish to consider CORBA, I just would like to let you know that
our OrbRiver/Ada runs on your targeted systems (OpenVMS/Gnat and
Tru64/Gnat).
I should recognize help from Thierry Lelegard for the port to OpenVms.


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"Scorpion" <erber@yahoo.de> a �crit dans le message de news:
3df79d5a$1@news.swissonline.ch...
> Hello,
>
> we use Dec Ada in a homogenous VMS AXP environment. Now, we want to
migrate
> to Gnat Ada95 first and then to Gnat Ada on Tru64 Unix (both alpha
hardware
> and little endian). We are using an RPC mechanism, which tranfers binary
> data, represented by complex Ada variant records. Is there a chance, that
we
> can continue doing this between OpenVMS AXP and Tru64 AXP? Or do we have
to
> introduce data mashalling in any case.
>
> best regards
>
> Jakob
>
>

Re: Gnat Ada binary compatibility

[Jakob Erber]

> We solved that by using marshalling. This approach is correct, portable
> and inter-operable. If you do not want to do the marshalling yourself,
> you may use some middleware that will do this for you (CORBA or DSA,
> although DSA is non-inter-operable outside GNAT).
>

Could you please point me to a good documentaion for DSA?

regards

Jakob

Re: Gnat Ada binary compatibility

[Thierry Lelegard]

> Could you please point me to a good documentaion for DSA?

DSA is the "Distributed Systems Annex", that is to say the annex E of the
Ada95 RM. The only implementation I am aware of is Glade, based on GNAT. 

-Thierry

Re: Gnat Ada binary compatibility

[Simon Wright]

Thierry Lelegard <thierry.lelegard@canal-plus.fr> writes:

> We solved that by using marshalling. This approach is correct,
> portable and inter-operable. If you do not want to do the
> marshalling yourself, you may use some middleware that will do this
> for you (CORBA or DSA, although DSA is non-inter-operable outside
> GNAT).

It's possible to use the GLADE version of System.Stream_Attributes on
its own to get minimal-effort marshalling.