I keep getting this warning every time I compile the following code.
Can anyone please tell me what I am doing wrong.
Also, the printf(head->data) keeps saying that printf's argument is invalid. How do I print head's data?
Any help is appreciated.
Thanks,

#include<stdio.h>
#include<malloc.h>

typedef struct
{
  int data;
  struct element *next;
}node;

 main()
{
  node *head;
  insert(&head);
  printf(head->data);
}


 insert(node **head)
{
  node *newElem;
  newElem= (node *)malloc (sizeof(node));
  if(!newElem)
  {
    return 0;

  }
 newElem->next=head;
 head=newElem;
 head->data=45;
  return 1;
}

>printf(head->data);
printf takes a string as the first argument, not an integer. You probably just forgot to add the format string, which would make the line look like this:

printf("%d\n", head->data);

If you don't mind, I'll make a few unrelated comments:

>#include<malloc.h>
malloc.h isn't a standard header, and it's certainly not the one you should be including for malloc. Include stdlib.h instead.

>main()
The best definition of main is:

int main ( void )
{
  /* Your code here */

  return 0;
}

This guarantees that you'll be able to compile now and in the forseeable future. Also, when you omit the return type, it's int. Just because you didn't say int explicitly doesn't mean you can omit the actual return value too.

>insert(node **head)
Once again, be sure to be explicit about your return types.

>newElem= (node *)malloc (sizeof(node));
This isn't built for maintenance. If you decide to change the name of the structure ("node" is surprisingly popular, and C doesn't handle naming conflicts very well), you have to change each and every occurrence of it in your code. You can get rid of the specific type entirely by doing this:

newElem = malloc ( sizeof *newElem );

The cast isn't required in C, and because sizeof doesn't evaluate the operand, you can dereference the pointer all you want and nothing bad will happen. The plus side is that this trick is an easy way of getting the size of the thing a pointer points to without knowing ahead of time. :)

I hope that your struct was just missing the element part:

typedef struct [B]element[/B]
{
  int data;
  struct element *next;
} node;

You aren't likely to compile properly if you use struct element without first tagging it...

Hope this helps.

I hope that your struct was just missing the element part:

typedef struct [B]element[/B]
{
  int data;
  struct element *next;
} node;

You aren't likely to compile properly if you use struct element without first tagging it...

Hope this helps.

That's weird because my program is working even without doing it. :-/

> That's weird because my program is working even without doing it
Seems to me that you're compiling your C code with a C++ compiler then.
Try renaming your prog.cpp file to be prog.c then see what happens.

> That's weird because my program is working even without doing it
Seems to me that you're compiling your C code with a C++ compiler then.
Try renaming your prog.cpp file to be prog.c then see what happens.

My bad, I guess when I copy pasted the code it somehow got lost. :)

I have it in my program. Thanks guys!!:icon_cheesygrin:

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