C语言入栈弹栈问题?

#include <stdio.h>
#include <stdlib.h>
struct Stack{
    int data;
    struct Stack *next;
}; 

void Push(Stack **stack,int data){
    Stack *t = (struct Stack*)malloc(sizeof(struct Stack));
    t->data = data;
    t->next = *stack;
    *stack = t;
}
void pop(Stack *stack){
    if(!stack){
        printf("栈已空\n"); 
        return;
    }
    Stack *p = stack;
    printf("%d",p->data);
    free(p);
    stack = stack->next; 
}
int main() {
    Stack *stack =NULL;
    Push(&stack,2);
    Push(&stack,4);

    pop(stack);pop(stack);
    return 0;
}

入栈2和4
弹出为什么是一串数字??