Question

In libname.h:

int add_libname(int, int);

In libname.c:

#include "libname.h"

int add_libname(int a, int b)
{
  return a+b;
}

I can build the shared library this way:

gcc -shared -fPIC libname.c -o libname.so

But I can’t use it in another programe test.c:

#include <stdio.h>
#include "libname.h"

int main(int argc, char* argv[])
{
  printf("%d\n", add_libname(1,5));
}

Reporting undefined reference to add_libname when I try to build it..

What’s wrong here?

Answer 1

Because add_libname takes (int, int) you’re giving it (1+5 = 6) or just (int)

I think you meant
add_libname(1, 5);

Also to compile it correctly you must use gcc like so

gcc -o myapp test.c -L. -lname

the lib part of libname is ignored as it is implicit