tmp.c

#include <stdio.h>	
#include <stdlib.h>	

    typedef struct stack
    {
            char *arr;//array of chars
            int size;
            int top;
    }stack;
     
void grow(stack *);
void stackInit(stack *);
     
    int main(int argc, char const *argv[])
    {
            stack st1;
	    stackInit(&st1);

	    st1.arr[0] = 'H';
	    st1.arr[1] = 'i';
	    st1.arr[2] = '!';
	    st1.arr[3] = 0;
     
		printf("%d: %s\n", st1.size, st1.arr);

            grow(&st1);

		printf("%d: %s\n", st1.size, st1.arr);

            return 0;
    }

void stackInit(stack *s) {
	s->size	= 4;
	s->top	= 0;
	s->arr	= malloc(4 * sizeof(char));
}
     
void grow(stack *pst)
    {
        char *temp;//Create temp array
        temp = (char *) malloc (((pst->size) + 1) * sizeof(char));//Allocate the correct amount of space for the temp array.
        int i;
    
if (NULL == temp) {
	return;
}	
       
        for (i=0;i<pst->size;i++)//Put all values from the old array into the temp array.
            (temp)[i]=(pst->arr)[i];
     
        free(pst->arr);//Free the old array's memory.
        pst->arr=temp;//Point the old array at the adress of the new array.
        pst->size=(pst->size)+1;
     
    }