Thread: Use of uninitialized value of size 4

Im pretty new to C, and am looking for an explanation of why I am getting this error message.

Code:

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

struct node {
   int first;
   struct node *rest;
};

struct node *cons(int fst, struct node *rst) {
   struct node *new = malloc(sizeof(struct node));
   new->first = fst;
   new->rest = rst;
   return new;
}


struct node *insert(struct node *lst1, int n) {
   struct node *temp;
   temp->first = n;
   temp->rest = lst1;
   return temp;
}


int main(void) {
   struct node *a = cons(2,cons(3,cons(6,NULL)));
   struct node *c = insert(a, 10);
}

This is the valgrind message I get:

Code:

= Use of uninitialised value of size 4
=    at 0x80483FB: insert (test.c:19)
=    by 0x804845F: main (test.c:27)
=  Uninitialised value was created by a stack allocation
=    at 0x80483F2: insert (test.c:17)
= Process terminating with default action of signal 11 (SIGSEGV)
=  Bad permissions for mapped region at address 0x8049FF4
=    at 0x80483FB: insert (test.c:19)
=    by 0x804845F: main (test.c:27)

I know this is a simple problem but I just don't understand what is going on!

how would I make it point to something? Like does it have to point at a specific type?