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Date: 3 Jun 93 13:31:21 GMT
From: pa.dec.com!e2big.mko.dec.com!dbased.nuo.dec.com!digits.enet.dec.com!brett
@decwrl.dec.com  (Bevin R. Brett)
Subject: Re: VMS Ada from C questions
Message-ID: <1993Jun3.123650.8927@dbased.nuo.dec.com>
List-Id: <comp.lang.ada>

In article <C80nEy.AvJ@shuksan.ds.boeing.com>, scott@shuksan.ds.boeing.com (Sco
tt Moody) writes...
>Does anyone have experience  calling VMS Ada from C?
> 
>I can't seem to the the argument sizes correct, or
>the argument passing mechanism.
> 
>There is a pragma export_procedure, but nothing to
>tell the passing mechanism.
> 
>Now I can call C from Ada, and tell it to pass by value,
>but there isn't a export version.
> 
>Anyone use VMS Ada as a non-main program??
> 
>Thanks..
> 
>-- 
>Scott Moody   (206) 773-4313   "There are no answers .. just cross references"
>     scott@shuksan.boeing.com  
>     uunet!bcstec!shuksan!scott

--

The V3.0 version of DEC Ada for OpenVMS VAX Systems, and for OpenVMS AXP system
s
both support specifying mechanism and result_mechanism in the Export_[proc|func
]
pragmas with the same syntax as the Import_[proc|func] pragmas.

You should have this version installed by now, it has been out for quite a
while.  [The VAX version is also the one that supports Smart Recompilation, if
you get the Professional Development Option].

Prior to that, the only way was (a) have the C code pass a pointer, to get
Reference semantics, or (b) gross hacks involving taking the address of a
in parameter of a large record type and unchecked_converting it to Integer [or
whatever].

--

To see how to use Ada units as a non-main program,  look up ACS EXPORT in the
Developing Ada Programs manual.

--

/Bevin
DEC Ada team