At first I want to apologize for my English. I want to rewrite my Java program to D. I have problem with shared library and dlopen() function.

calc_mean.d:

extern(C){
     double mean(double a, double b) {
             return (a+b) / 2;
     }
}

dmd -fPIC calc_mean.d -c
gcc -shared -Wl,-soname,libmean.so.1 -o libmean.so.1.0.1  calc_mean.o -m32


test.d:

import std.stdio;
import std.c.linux.linux ;

public void main(){
     void *handle;
     double (*reff)(double, double);

     handle = dlopen("./libmean.so.1.0.1", RTLD_NOW);

     char *errstr = dlerror();

     if(errstr != null)
          printf ("A dynamic linking error occurred: (%s)\n", errstr);

     *cast(void **)(&reff) = dlsym(handle, "mean");
     errstr = dlerror();

     if(errstr != null)
          printf ("A dynamic linking error occurred: (%s)\n", errstr);

     writefln((*reff)(1,12));
}



dmd test -L-ldl

./test :

./test
A dynamic linking error occurred: (./libmean.so.1.0.1: undefined symbol:
_Dmodule_ref)
A dynamic linking error occurred: (./test: undefined symbol: mean)
Segmentation fault

I am 17, so I am novice programmer. I don't know what I am doing wrong. Please help me.

Michał Cieślak wrote:
> At first I want to apologize for my English. I want to rewrite my Java program to D. I have problem with shared library and dlopen() function.
> 
> [snip]

Last time I checked, DMD couldn't generate position-independent code on linux, which means it can't compile shared libraries.

You might have more luck with the GDC compiler, but since I don't use linux, that's just a guess.

You might also want to have a look at DDL <http://www.dsource.org/projects/ddl/>.

	-- Daniel

Dnia Fri, 24 Aug 2007 17:08:54 +1000
Daniel Keep <daniel.keep.lists@gmail.com> napisał/a:


> Last time I checked, DMD couldn't generate position-independent code on linux, which means it can't compile shared libraries.

True. I was hardly trying but DMD can't do this.

> You might have more luck with the GDC compiler, but since I don't use linux, that's just a guess.

GDC is also for Win32.

-- 
Witold Baryluk, aleph0

Witold Baryluk wrote:
> Dnia Fri, 24 Aug 2007 17:08:54 +1000
> Daniel Keep <daniel.keep.lists@gmail.com> napisał/a:
> 
> 
>> Last time I checked, DMD couldn't generate position-independent code
>> on linux, which means it can't compile shared libraries.
> 
> True. I was hardly trying but DMD can't do this.
> 
>> You might have more luck with the GDC compiler, but since I don't use
>> linux, that's just a guess.
> 
> GDC is also for Win32.

I think his point is that the issue is on Linux. There's a difference between Linux .so libraries and Windows DLLs: the latter don't require position-independent code (IIRC they contain relocation info) and DMD/Windows can in fact create them.