ANUS C

Hi /prog/,
so I'm new into ANSI C because you guys always advocate for it. I crammed together this piece of code but it seems that I did not really understand why I had to use a double-reference in the function call. Could you please enlighten me!


#include <stdio.h>
#include <stdlib.h>
#define MAX 10

typedef struct stack{
    int value;
    struct stack *next;
    } STACK;

STACK s;

void push(STACK **, int);
int pop(STACK **, int *);

int main(void){
    STACK *p, **pp;
    p = &s; pp = &p;
    *pp = NULL;

    int i, x, error;
   
    for(i = 0; i < MAX; i++){
        push(pp, i);}

    for(i = 0; i < MAX+1; i++){
        x = pop(pp, &error);
        if(!error) printf("pop (): %d\n", x);
        else       printf("error: stack empty\n");}
   
    return 0;
    }

void push(STACK **s, int item){
    STACK *new;
    new = (STACK *) malloc(sizeof(STACK));
    new->value = item;
    new->next = *s;
    *s = new;}

int pop(STACK **s, int *error){
    STACK *old = *s;
    int oldValue;
    if(*s){
        oldValue = old->value;
        *s = (*s)->next;
        free(old);
        *error = 0;}
    else{
        oldValue = 0;
        *error = 1;}
    return(oldValue);}

>>11
Why use malloc when the computer can manage the memory for you?