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Old 08-25-2009, 02:45 AM   #1
LQ Newbie
Registered: Aug 2009
Posts: 2

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Question reverse dependency problem while dlopen shared lib

Hi everyone ,
I am using loading a shared library dynamically in my code using dlopen() & then calling a function of it which in turn calling the function of my own program .But this is giving "undefined reference" problem .Please see the following snap of the code :

Code for main Program :
#include <dlfcn.h>
#include "sample_header.h"
void main_fun(int k)
printf("\n ***** In Main Fun : %d",k);
void main()
char *error;
void (*sample_fptr)(int);
void *handle = dlopen ("./", RTLD_LAZY);
if (!handle)
printf ("\n%s\n", dlerror());

sample_fptr = dlsym(handle, "shared_fun");
if ((error = dlerror()) != 0)
printf ("\n%s\n", dlerror());

printf("Done ........\n");

compilation command used : gcc -ldl sample.c
//sample_header declaration is :

#include <stdio.h>
void main_fun(int k);


Code for sample_shared.c :
#include "sample_header.h"
void shared_fun(int k);
void shared_fun(int k)

compilation command : gcc -shared -Wall sample_shared.c -o

Result @ runtime : ./ undefined symbol: main_fun

Any suggestion to resolve this issue is appreciated.

Thanx in Advance
Old 08-25-2009, 08:48 AM   #2
Registered: May 2002
Location: dracut MA
Distribution: Ubuntu; PNE-LE; LFS (no book)
Posts: 598

Rep: Reputation: 109Reputation: 109
You need to use -rdynamic and -fPIC.

Here are the compilation commands to use:

gcc -o sample -ldl -fPIC -rdynamic sample.c

gcc -shared -rdynamic -fPIC -Wall -o sample_shared.c


dependency, library, reverse, shared

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