Question

I am looking at a C client-server program and encountered this problem. The compiler complains that the function “return with a value, in function returning void”.

My question is, what is the point of returning (NULL) as opposed to simply return? Is this perhaps to avoid the caller from getting garbage back?

void *ThreadMain(void *threadArgs)
{
    int clntSock;                   /* Socket descriptor for client connection */

    /* Guarantees that thread resources are deallocated upon return */
    pthread_detach(pthread_self()); 

    /* Extract socket file descriptor from argument */
    clntSock = ((struct ThreadArgs *) threadArgs) -> clntSock;
    free(threadArgs);              /* Deallocate memory for argument */

    HandleTCPClient(clntSock);

    return (NULL);
}

Answer 1

 "return with a value, in function returning void".

You have some other function which has a return type void and you are returning a value from that function. But the function you posted is not that function. Basically the function you have posted has nothing to do with your problem 🙂

The one you posted has a return type void * which is different from void. So this is not the function the compiler complains about. Look at other functions in your code that return void (not void *) and you have a return in one (or more) of them.