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From: Stephen Leake <Stephen.Leake@gsfc.nasa.gov>
Subject: import a C function returning char *
Date: 1999/02/03
Message-ID: <ud83r4c6w.fsf@gsfc.nasa.gov>#1/1
X-Deja-AN: 440256910
Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA
Newsgroups: comp.lang.ada
Date: 1999-02-03T00:00:00+00:00
List-Id: <comp.lang.ada>

I need to import the C function:

char *sbs_read_error (void);

I'd like to use the facilities in Interfaces.C, but since there is no
char_ptr type, I'm not clear what the correct method is. LRM B.3 (63
.. 75) talk about various parameter passing modes, but there's no
discussion of function results.

Since all parameters of an array type are passed by pointers, I could
assume function results are also passed by pointer, and try:

declare

   function Sbs_Read_Error return Interfaces.C.char_array;
   pragma Import (C, Sbs_Read_Error, "sbs_read_error");

   Result : String (1 .. 30);
   Result_Last : Natural;

begin

   Interfaces.C.To_Ada (Sbs_Read_Error, Result, Result_Last);

   Text_Io.Put_Line (Result (1 .. Result_Last));

end;

Is this going to work (I'll get around to compiling this soon)? I'm
using GNAT 3.11p and ObjectAda 7.12 on Windows NT; what about other
Ada compilers?

-- Stephen Leake