Simulate simple stack function

Question

I am still learning the C language. I have a problem to simulate a simple stack function, such as push, pop and so on. I found that the date and next are not initialized in the PTAIL. At that time, the program end. Is that counting as a memory leak?

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
typedef struct Node{
    int date;
    struct Node * next;
}Node,*PNode;

typedef struct Stack{
    PNode pHead;
    PNode pTail;
}Stack;

void init(Stack *pS){  
    PNode n=(PNode)malloc(sizeof(Node));
    pS->pHead=n;
    pS->pTail=n;
    n->next=NULL;
}

void push(Stack *pS,int val){ 
    PNode p=(PNode)malloc(sizeof(Node));
    p->date=val;
    p->next=pS->pHead;
    pS->pHead=p;
}

void travel(Stack *pS){ 
    PNode p=pS->pHead;
    while(p->next){  
        printf("%d ",p->date);
        p=p->next;
    }
    printf("\n");
}

int main(void){

    Stack s;
    init(&s);  
    push(&s,1);
    travel(&s); 

    push(&s,1);
    travel(&s); 
    system("pause");
    return 0;
}

Answer 1

Every malloc should be paired with a free(). You didn't write/show your pop() function, but that's the place. If a memory buffer/object is not freed then it's a memory leak.

You allocated an empty first item in Init()m that's not needed.

Stacks usually do not need a tail, just a head. You also never update the tail...

Answer 2

You allocate unnecessary node on init. What is more, you do not initialize date member of it. Remove the node creation:

void init(Stack *pS) {  
    pS->pHead = NULL;
    pS->pTail = NULL;
}

Casting is unnecessary on push.

PNode p = malloc(sizeof(Node));

Your travel function is checking for p->next even if p can be NULL. Change the while test:

void travel(Stack *pS) { 
    PNode p = pS->pHead;
    while(p) {  
        printf("%d ", p->date);
        p = p->next;
    }
    printf("\n");
}