Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Message-ID: <41ECE515.8030905@free.fr>
Date: Tue, 18 Jan 2005 11:29:41 +0100
From: David Marteau <daim DOT project AT free DOT fr>
Reply-To: daim DOT project AT free DOT fr
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624
MIME-Version: 1.0
To: svoboda AT cs DOT cmu DOT edu
Cc: cygwin AT sourceware DOT org
Subject: Re: Building DLL's using g++, not gcc
References: <200501171746 DOT 26708 DOT svoboda AT cs DOT cmu DOT edu>
In-Reply-To: <200501171746.26708.svoboda@cs.cmu.edu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-IsSubscribed: yes

Hi,

The way symbol names are built in dll differs  if they are related to c 
call convention or to c++ call, and that could be your problem. When 
compiling hello.c with gcc, your exported symbol corresponds to C 
calling convention.
 
When compiling dll with g++, you should declare your exported function 
as 'extern "C"' in hello.c.

David Marteau

svoboda AT cs DOT cmu DOT edu wrote:

>I've been trying to build a DLL using g++, and given the problems I was 
>having, I decided to try a 'toy' example, which is available at:
>	http://cygwin.com/cygwin-ug-net/dll.html
>I tweaked the two files around thusly:
>
>
>hello.C:
>-----
>#include <stdio.h>
>int hello() { printf("Hello World\n");}
>-----
>
>main.C:
>-----
>#include <stdio.h>
>typedef void (*fn_type)();
>
>extern "C" {
>  int dlopen(char*);
>  int dlsym( int, char*);
>}
>
>int main() {
>  int handle = 0;
>  fn_type fn = 0;
>  if ((handle = dlopen( "hello.dll")) == 0) {
>    printf( "Cannot open hello.dll\n");
>  }
>  if ((fn = (fn_type) dlsym( handle, "hello")) == 0) {
>    printf( "Cannot open hello()\n");
>  }
>  fn();
>}
>-----
>
>This way, hello.C is a valid C or C++ application, and main.C is a
>valid C++ application. I build main.exe by:
>
>	g++ -o main main.C
>
>If I build hello.dll this way, it works:
>
>	gcc -shared -o hello.dll hello.C
>	./main
>	Hello world!
>
>But if I build hello.dll this way, it doesn't work:
>
>	g++ -shared -o hello.dll hello.C
>	./main
>	bash: [2084: 2] testaddr: Inappropriate ioctl for device
>
>Why? What am I doing wrong?
>
>~David Svoboda
>
>  
>



--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/