Pointers and references: Difference between revisions

The following code snippet shows a practical example of using pointers in C with structs. Note there are many ways to access to a value using the * operator.

<lang c>#include <stdio.h>

#include <stdlib.h>

typedef struct {

int val;

} num;

int addNodes(num **array, int elems);

int main(void) {

int numElems, i;

num *arr = NULL;

numElems = addNodes(&arr, 10);

for (i = 0; i < numElems; i++) {

printf("%d) %d\n", i+1, arr[i].val);

}

free(arr);

return 0;

}

int addNodes(num **array, int elems) {

num *temp = NULL;

int i;

for (i = 0; i < elems; i++) {

temp = realloc(*array, (i+1) * sizeof **array);

if (temp == NULL) {

free(*array); return -1;

} else {

*array = temp;

}

(*array)[i].val = i;

// Alternatives:

// ((*array)+i)->val = i; // or

// (*((*array)+i)).val = i;

}

return i;

}</lang>