Simple dll usage (never use dlopen if your program just needs to load the library at startup!!)

gistfile1.txt

/* add.c */
#include <stdio.h>
float add(float a, float b) { return a + b; }
//gcc -shared -o libadd.so add.c -fPIC

/* main.c */
#include <stdio.h>
extern float add(float a, float b);
int main() { printf("Result: %f\n", add(3.0, 4.0)); return 0; }
//gcc main.c -L. -ladd
//./a.out