Returning Array from function in C

Question

For some reason, my function is only returning the first element in my array and I cannot figure out why the rest of the array goes out of scope. The function takes two integer

Answer 1

my function is only returning the first element in my array and I cannot figure out why the rest of the array goes out of scope.

No, it returns a pointer to the first element - and the entire array goes out of scope. Any data you see that happens to remain as it was in the function is by luck rather than judgement, and you cannot use it as it is released for use by other functions.

Arrays are not first class data types in C - you cannot return an array by copy.

The normal solution is to have the array owned by the caller and to pass its address and size to the function.

int* func( int* arr, int arrlen )
{
    // write to arr[0] to arr[arrlen-1] ;

    return arr ;
}

int main()
{
    int array[256] ;
    func( array, sizeof(arr)/sizeof*(*arr) ) ;
}

Other less common and generally ill-advised possibilities are either to return a struct containing the array (a struct is a first class data type), but to do that is somewhat inefficient in many cases, or to dynamically allocate the array within the function, but it is not a particularly good idea since the caller has the responsibility of freeing that memory and may not be aware of that responsibility - it is a recipe for a memory leak.