//ross.c: In function ‘Pop_Task’:
//ross.c:96: error: incompatible types when assigning to type ‘struct Task *’ from type ‘Task’

typedef struct Task {
  int task_number;
  Playfield *pf;
  Move *moves;
  int sx;
  int sy;
  int depth;
} Task;

Task *Pop_Task() {
  Task *task;

  pthread_mutex_lock(&stack_mutex);
  if(task_stack.pointer < 0) {
    pthread_mutex_unlock(&stack_mutex);
    return NULL;
  }
  task = task_stack.tasks[task_stack.pointer];
  task_stack.pointer--;
  pthread_mutex_unlock(&stack_mutex);

  return task;
}