Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!math.fu-berlin.de!mailgzrz!w203zrz!duns1222
From: duns1222@w203zrz.zrz.tu-berlin.de (Martin Dunschen)
Newsgroups: comp.lang.eiffel
Subject: C and Eiffel ?
Message-ID: <702@mailgzrz.tu-berlin.de>
Date: 6 Jun 91 18:01:34 GMT
Sender: news@mailgzrz.tu-berlin.de
Distribution: world
Organization: TU-Berlin
Lines: 135
Nntp-Posting-Host: w203zrz.zrz.tu-berlin.de
Originator: duns1222@w203zrz

Hello,

We have a problem calling eiffel from C.

We typed in the example as given in "Eiffel: The Language" Version 2.2, page
221 (but we use version 2.3 level 4) and tried to create an executable 
programm by adding an appropriate (?) "main.c". Of course we got errors 
from "ld" saying, that there are undefined symbols. Okay, so we hacked in
a toy class calling this given example. Compiled with "es" everything works
fine. Now we want to use this in conjunction with eiffel classes compiled to C.
To get these C-versions of the system's classes we generated a C-package by
changing the SDF. 

Is this necessary, or is there another way to use the C verions of the 
system classes? 

We ran "identify A" in the directory containing the C-routines.
An archive was created.

But what now? When we try to link everything together with a self written main
"ld" complains about undefined symbols (eif_create, eif_rout, eif_attr, 
MakeStr), which we found in the archive-file in __eifc.o (most of them)!

To complete the confusion we add the sources of everything as a shell-archive.
Please try it and tell us, what we do wrong.

P.S: The reason we want to do this, is the interfacing from prolog to
     eiffel, e.g. create objects, call features. 
     The used prolog has a C interface.

Thank you all for your patience !!!

#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create:
#	.eiffel
#	neu.e
#	test.c
#	paket/my_main.c
# This archive created: Thu Jun  6 19:48:11 1991
export PATH; PATH=/bin:/usr/bin:$PATH
echo shar: "extracting '.eiffel'" '(477 characters)'
if test -f '.eiffel'
then
	echo shar: "will not over-write existing file '.eiffel'"
else
sed 's/^X//' << \SHAR_EOF > '.eiffel'
X------------ EIFFEL SYSTEM DESCRIPTION FILE -------------------
X--   For simple uses, just replace ``root_class_name'' below
X--   by the name of the root class of your system (lower case)
XROOT: neu
XUNIVERSE: $EIFFEL/library/structures $EIFFEL/library/support
XEXTERNAL: test.o
XNO_ASSERTION_CHECK (N): ALL
XPRECONDITIONS (Y): ALL
XALL_ASSERTIONS (N): ALL
XDEBUG (N):
XTRACE (N):
XOPTIMIZE (N): ALL
XGARBAGE_COLLECTION (N)
XC_PACKAGE (N): paket
XC_EXTERNAL: test.c
XMAKE:
XVISIBLE (N): neu
SHAR_EOF
if test 477 -ne "`wc -c < '.eiffel'`"
then
	echo shar: "error transmitting '.eiffel'" '(should have been 477 characters)'
fi
fi
echo shar: "extracting 'neu.e'" '(127 characters)'
if test -f 'neu.e'
then
	echo shar: "will not over-write existing file 'neu.e'"
else
sed 's/^X//' << \SHAR_EOF > 'neu.e'
Xclass NEU
Xfeature
X	Create is
X	external test : INTEGER language "C"
X	do
X		io.putint (test ());
X	end; -- Create
Xend -- class NEU
SHAR_EOF
if test 127 -ne "`wc -c < 'neu.e'`"
then
	echo shar: "error transmitting 'neu.e'" '(should have been 127 characters)'
fi
fi
echo shar: "extracting 'test.c'" '(341 characters)'
if test -f 'test.c'
then
	echo shar: "will not over-write existing file 'test.c'"
else
sed 's/^X//' << \SHAR_EOF > 'test.c'
X#include "/cad01/Eiffel/files/_eiffel.h"
X#include <stdio.h>
Xextern OBJPTR eif_create ();
Xextern DATUM eif_rout();
Xextern int eif_attr ();
Xint test ()
X{
X  OBJPTR obj;
X  obj = eif_create("string", 10);
X  eif_rout(obj, "append", MakeStr("Hello world"));
X  printf("Size of Eiffel string is: %d\n",(int32) eif_attr (obj, "size"));
X  return 25;
X}
SHAR_EOF
if test 341 -ne "`wc -c < 'test.c'`"
then
	echo shar: "error transmitting 'test.c'" '(should have been 341 characters)'
fi
fi
echo shar: "extracting 'my_main.c'" '(22 characters)'
if test -f 'my_main.c'
then
	echo shar: "will not over-write existing file 'my_main.c'"
else
sed 's/^X//' << \SHAR_EOF > 'my_main.c'
Xmain ()
X{
X	test ();
X}
SHAR_EOF
if test 22 -ne "`wc -c < 'my_main.c'`"
then
	echo shar: "error transmitting 'my_main.c'" '(should have been 22 characters)'
fi
fi
exit 0
#	End of shell archive