bool is_something_ok(int param,SomeStruct* p) { bool is_ok = false; // check if is_ok if(is_ok) // set p to some valid value else // set p to NULL return is_ok; } this function return true and set p to a valid value if "something is ok" otherwise return false and set p to NULL Is that a good or bad design? personally, i feel uncomfortable when i use it. If there is no document and comment, i really don know how to use it. BTW:Is there some authoritative book/article about API design?