confusion about free(pointer) in c -

i trying implement stack using pointers, structure definition in code below. called push() function 3 elements (say: 2, 4, 6) insert. then, call function display(). it's showing 0. figured out reason because of free() function in push() function. but, don't know indeed happening there. should not use free() free allocated memory used temp in code? if so, why?

#include<stdio.h> //#include<unistd.h> #include<stdlib.h> // malloc ,calloc, free avail here void push(); void pop(); void display(); struct stack {     int data;     struct stack *next; };  struct stack *start = null;  void push() {     int ele;     struct stack *temp, *p;     printf("entere element\n");     scanf("%d", &ele);     temp = (struct stack *) malloc(sizeof(struct stack));     temp->data = ele;     if (start == null) {         start = temp;         start->next = null;     } else {         p = start;         while (p->next != null) {             p = p->next;         }         p->next = temp;         temp->next = null;     }     free(temp); } 

void push(){                int ele;                struct stack *temp,*p;                printf("entere element\n");                scanf("%d",&ele);                temp=(struct stack *)malloc(sizeof(struct stack ));                temp->data=ele;                if(start==null){                start=temp;                start->next=null;             }            else{                 p=start;                 while(p->next !=null){                                        p=p->next;                  }                 p->next=temp;                temp->next=null;             }              free(temp); // don't free temp here !             } 

you have free pointer if don't need more. think case, since don't use temp, doesn't. parameter of free valid memory address. temp valid memory address, you're assigning temp start ! : free(tmp) same free(start), , that's not want.