Hi all,

I am trying to link a library "libfunc1.so" at runtime. This library is having dependency on "libfunc2.so" library. As per the manpage the dlopen() should load the dependent libraries automatically. But it's not happening for me. When I compile an execute the following executable, it throws an error as
---
tsf:skumar % ./a.out
ERROR:: ld.so.1: a.out: fatal: relocation error: file ./libfunc1.so: symbol func2: referenced symbol not found
tsf:skumar %
---

my program looks as follows

=======
#include <stdio.h>
#include <dlfcn.h>
#include <link.h>

main( int argc, char *argv[])
{

int (*func1)( int, int);
void *handle;
int result;

if (( handle = dlopen("libfunc1.so", RTLD_NOW | RTLD_GLOBAL)) == NULL )
{
printf( "ERROR:: %s\n", dlerror());
exit(1);
}
printf("Library loading is successful\n");

func1 = dlsym(handle, "func1");
if (func1 == NULL)
{
printf("ERROR:: %s\n",dlerror());
dlclose(handle);
exit(1);
}
result = (*func1)(2,3);
printf("\n result %d\n",result);

dlclose(handle);
}

=======

The library code is as follows

libfunc1.so
====
#include <stdio.h>
int func2( int a, int b);
int func1(int x, int y)
{
printf("\nIn func1()\n");
func2( x, y);
return (x+y);
}
====


libfunc2.so
====
#include <stdio.h>
int func2(int x, char y)
{
printf("\nIn func2()\n");
return (x*y);
}
====

What is compilation command line? I hope you didn't include -lfunc1 ?

Please perform 'ldd' on libfunc1.so and make sure it does, indeed, reference libfunc2.so.

I performed ldd it shows as below

===
tsf:skumar % ldd -r libfunc1.so
libgcc_s.so.1 => /export/home/diameter/library32//libgcc_s.so.1
libc.so.1 => /usr/lib/libc.so.1
libdl.so.1 => /usr/lib/libdl.so.1
/usr/platform/SUNW,Ultra-4/lib/libc_psr.so.1
symbol not found: func2 (./libfunc1.so)
tsf:skumar %
===

I think the library libfunc1.so is having lazy reference for the symbol "func2"

But it doesn't know it can be taken from libfunc2.so.. What is compilation line, anyway?

compilation line is as follows


$gcc -fPIC -c func1.c
$gcc -shared -o libfunc1.so func1.o
$gcc -fPIC -c func2.c
$gcc -shared -o libfunc2.so func2.o

$gcc -ldl -g testlib.c

Oh. Try
gcc -shared -o libfunc1.so func1.o -L. -lfunc2
and swap compiling order.

Yes, you'll need to link against func2 so it can find it at runtime.

Hmmm... Actaully I wanted dlopen() to load libfunc2.so automatically. But that doesn't seems to be happening.
Let me link it at compile time.

Anyways thanks you all for your valuable suggestions.

--ravin

It loads automatically - you don't to do anything on every load, but only if libfunc1.so is marked as dependent on libfunc2.so (which -l does).