#include <pthread.h>

typedef struct container_lock {
  int v;
  pthread_mutex_t l;
} container_lock_t ;

#define SYNC_START(x) {	     \
  container_lock_t *tmp = x; \
  {int *x = &tmp->v; pthread_mutex_lock(&tmp->l);

#define SYNC_END } pthread_mutex_unlock(&tmp->l);}

void* other_thread(void* arg){
  container_lock_t *cl = (container_lock_t *) arg;

  SYNC_START(cl);
  //now I hold the lock! cl is just a value in here
  *cl += 15;
  SYNC_END;
}

int main(){
  container_lock_t _cl;
  container_lock_t *cl = &_cl;
  pthread_mutex_init(&cl->l,0);

  pthread_t _other_thread;
  pthread_create(&_other_thread, NULL, other_thread, cl); 
  SYNC_START(cl);
  //now I hold the lock! cl is just a value in here
  *cl += 15;
  SYNC_END;
  pthread_join(_other_thread, NULL);
  return cl->v;
}