Nils Jonsson Nils Jonsson - 5 months ago 15
Linux Question

g++ custom dynamic library linking error undefined symbol

Ok, I'm looking for a solution for 2 days now. I didn't find anything to solve my problems.

What is currently going on?
So, I tried creating a dynamic library (.so) on Linux Mint Maya 13 with g++.

foolib.h:

#pragma once
#include <stdio.h>

void foo(
void
);


foolib.cpp:

#include "foolib.h"

void foo(
void
)
{
printf ("Hello World!\n");
};


main.cpp:

#include "foolib.h"

int main(
int argc,
char** argv
)
{
foo ();
};


I compiled these files with these instructions:

libfoo.so:

g++ -shared -o libfoo.so -fpic foolib.cpp


foo:

g++ main.cpp -o foo -L -lfoo


Creating libfoo.so works without any errors, but foo throws undefined reference ┬┤foo'. I copied sample code from several web pages and tried to compile it, always the same result.

The funny is, I can link do libdl.so (-ldl), load my .so and my function. What am I doing wrong?

I hope I could formulate my question correctly. Please tell me if I didn't. : )

Answer

You should use:

g++ main.cpp -o foo -L./ -lfoo

or

g++ main.cpp -o foo libfoo.so