correct way to change values of c pointers

Question

Sorry, another C pointer question.. I have a function func() that sorts an array, then get the largest and smallest integers. I\'m trying to put them inside pointer variables in

Answer 1

You need to pass the address of the pointer variables if you want to change what they are pointing at, otherwise a copy of the pointer variable is being changed inside the function (and is why it is correct within the function):

void func(int arr[], int** s, int** l, int n){
    /* snip */

    *l = &arr[n-1];
    *s = &arr[0];
}

func(arr, &s, &l, size);

This would leave s and l pointing to elements of the array arr. If you just wanted the values of integers then the alternative would be to define int variables in main() and pass their addresses to func() and copy the relevent values from the array:

void func(int arr[], int* s, int* l, int n){
    /* snip */

    *l = arr[n-1];
    *s = arr[0];
}

int s, l;
func(arr, &s, &l, size);

See this question from the C FAQ.