structure defintion vs declaration question

[Chad]

Given the following.....

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

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

int main(void)
{
struct node* head;

head = malloc(sizeof(struct node));
head->data = 1;
head->next = NULL;

head = head->next;

free(head);

return 0;
}


Is struct node *next defintion or declaration?

 

[vippstar]

Given the following.....

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

struct node {
int data;
struct node *next;

};

int main(void)
{
struct node* head;

head = malloc(sizeof(struct node));
head->data = 1;
head->next = NULL;

head = head->next;

free(head);

return 0;

}

Is struct node *next defintion or declaration?

It's a declaration.
See 6.7.2.1

 

[Anand Hariharan]

Given the following.....

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

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

int main(void)
{
struct node* head;

head = malloc(sizeof(struct node));
head->data = 1;
head->next = NULL;

head = head->next;

free(head);

return 0;
}


Is struct node *next defintion or declaration?

After noting vippstar's response to your immediate question ...
.... hope you are aware that your code is leaking memory.

Also, I'd suggest you review the currently active thread 'Pointer
dereference rather than sizeof' and see if you might reconsider how you
wrote your malloc statement.

- Anand

 

[Chad]

After noting vippstar's response to your immediate question ...
... hope you are aware that your code is leaking memory.

Also, I'd suggest you review the currently active thread 'Pointer
dereference rather than sizeof' and see if you might reconsider how you
wrote your malloc statement.

Okay, how is the code leaking memory? I should see it, but for some
reason, I don't.

 

[vippstar]

Okay, how is the code leaking memory? I should see it, but for some
reason, I don't.

I did not review your code, just answered your question.
However, your code practically does this:

p = malloc();
/* ... */
p = NULL;
free(p);

(note: free(NULL) is defined to do nothing)

Not only you leak memory, but you fail to check the return value of
malloc, so you are also possibly dereferencing a null pointer.