Pointer pointing to an empty array

Question

I have a pointer that is pointing to the start of an array, but I need to check that it is unallocated. I thought of dereferencing the pointer and checking if NULL but that leads to a type error. Can anyone see what I'm doing wrong?

int mydispose(int *array){
    int i = 0;

    if(*array == NULL){
            return 1;
    }

    return ;

}

EDIT: Sorry if I was unclear: I have a pointer that points to the start of an array, but I wish to check whether the array is empty.

Answer 1

*array == NULL is wrong. You are dereferencing the pointer first (which could lead to a segfault if the pointer really is null) and then comparing its int value to a pointer value. Moreover, your compiler will perfectly accept that erroneous expression if NULL is defined as just 0 and not (void *) 0.

You should be checking array == NULL to see if the passed pointer refers to anything, and then dereference it only in case it's not NULL.

Be aware, however, that dereferencing a non-null pointer isn't guaranteed to be a safe operation either. If the pointer contains a garbage value because it was allocated on the stack and not initialized, or if it refers to a deallocated region of memory, nasty bugs can happen.

Answer 2

You want if (array == NULL) -- but unless you first initialize array to NULL, it won't do any good either. I think you'd be better off backing up and telling us a bit more about what you're trying to accomplish, and trying to get help trying to accomplish your overall goal.