/* Compile with gcc -fPIC -g -c -Wall lib.c; gcc -shared -Wl -o lib.so lib.o */

#include <pthread.h>
#include <stdio.h>

typedef void callback_t(void);

callback_t* callback_fn;

void *async_cb(void *dummy)
{
    (*callback_fn)();
    (*callback_fn)();
    pthread_exit(NULL);
}

int callback(callback_t* cb_fn)
{
   pthread_t thread;
   int rc;

   printf("In callback: creating thread\n");
   callback_fn = cb_fn;

   rc = pthread_create(&thread, NULL, async_cb, (void *)NULL);

   if (rc) {
       printf("ERROR; return code from pthread_create() is %d\n", rc);
       return(-1);
   }
   return(0);
}