Question

Here is a small program I wrote, (I am still writing it), however till this point the program on compilation should not be giving any error as per my understanding.

#include <stdio.h>
#include <stdlib.h>
struct node t1 {
        int data;
        struct node *next, *prev;
};
struct node *root;
root = NULL;
int main()
{
        int i, j, choice, count;
        printf("enter choice\n");
        scanf("%d", &choice);
        count = 0;
        while (choice == 1) {
                printf("enter a data element");
                scanf("%d", &j);
                count++;
        }

}

void push()
{
}

void pop()
{
}

The error I get is

 cc linklist.c
linklist.c:3:16: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘{’ token
linklist.c:8:1: warning: data definition has no type or storage class [enabled by default]
linklist.c:8:1: error: conflicting types for ‘root’
linklist.c:7:14: note: previous declaration of ‘root’ was here
linklist.c:8:8: warning: initialization makes integer from pointer without a cast [enabled by default]

I use gcc and Ubuntu 11.04.
What is the reason that upon compiling the code I get above warning.

Answer 1

struct node *root;
root = NULL;

You can’t assign like that outside a function. Drop the root = NULL since it’s implicit for objects with static storage (such as global variables).

EDIT

As spotted by Tom Dignan the struct declaration is also wrong:

struct node t1 { ... };
            ^^