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Path: utzoo!attcan!uunet!lll-winken!ames!xanth!mcnc!rti!jb
From: jb@rti.UUCP (Jeff Bartlett)
Newsgroups: comp.lang.ada
Subject: Re: bug in DEC compiler??
Summary: importing with Dec Ada
Message-ID: <2757@rti.UUCP>
Date: 27 Jan 89 03:48:47 GMT
References: <8901260051.AA26048@ajpo.sei.cmu.edu>
Organization: Research Triangle Institute, RTP, NC
List-Id: <comp.lang.ada>

In article <8901260051.AA26048@ajpo.sei.cmu.edu>, gerhardt@AJPO.SEI.CMU.EDU writes:
> We have tried to use the SAIC X window binding with the DEC ACS
> compiler.
 
> We are having problems with what looks like a bug in DEC ACS Ada.
 
> The code fragment looks like :
 
> 	type FOO is record... end record;
> 	type CLIST is access FOO;
> 	procedure EXT ( A : in out SYSTEM.ADDRESS ) is ... end;
> 	pragma INTERFACE (EXT, SYSTEM.ADDRESS, VALUE);
> 	LOC : CLIST;
> begin
> 	EXT(LOC.all.'ADDRESS);
 
> This code compiles but when it runs it loses the address when it gets
> to the externaL procedure (WRITTEN IN C).  
 
> When an unchecked conversion to SYSTEM.ADDRESS is done on LOC and that
> is used as the calling parameter, it works ok.  Am I missing
> something, or is this
> a plain old bug??  Thanks in advance

This works:

-- zip.ada

with SYSTEM;
procedure ZIP is

   type FOO is
	record
	BAR : INTEGER;
	end record;

   type CLIST is access FOO;

   procedure EXT( A : SYSTEM.ADDRESS );

   pragma interface(C,EXT);
   pragma import_procedure(EXT,"EXT",mechanism=>value);

   LOC : CLIST;

begin
   LOC := new FOO;

   LOC.BAR := 5;

   EXT(LOC.all'address);
end ZIP;

-- ext.c

struct foo {
  int bar;
};

ext( p )
   struct foo *p;
{
   printf("p->bar = %d\n", p->bar );
}

-- run.com

$ acs create library [.adalib]
$ acs set library [.adalib]
$ ada zip
$ cc ext
$ acs export/main zip
$ link zip,sys$input/option
	ext.obj
	sys$library:vaxcrtl/share
$ run zip
$ exit

---------------

  This was verified with DecAda v1.3.  for more info see "VAX Ada Programmer's
  Run-Time Reference Manual", section 4.4 "Using the Import and Export
  Pragmas", pages 4-14 to 4-26.  Hope this helps.

Jeff Bartlett
Center for Digital Systems Research		jb@rti.rti.org
Research Triangle Institute, RTP, NC		rti!jb@mcnc	mcnc!rti!jb

> 
> MArk Gerhardt
> ESL, INC
> reply : gerhardt@ajpo.sei.cmu.edu