Thread: Segmentation fault with Malloc

Hi everyone,
Just a quick background, i'm in my first year of university and have only doune maybe 6-7 weeks of C so try and keep things simple

I was trying to understand linked lists so was following the tutorial :
Cprogramming.com Tutorial: Linked Lists

Code:

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

struct node { char c; struct node *next;};

main()
{
	struct node *root; // Root node of list
	struct node *linkptr; // Pointer to link the nodes;
	
	root = malloc(sizeof(struct node));
	root -> next = 0;
	root -> c = 'L';
	linkptr = root;
	
		while( linkptr != NULL )
		{
			printf("%c\n",linkptr->c);
			//printf("in loop");
		//	scanf("%c",&(linkptr -> c));
			linkptr = linkptr -> next;
		}
		
	
	
	/* Creates a list a node at the end of the list*/
	
	//linkptr -> next = malloc(sizeof(struct node));
	linkptr->next = malloc(sizeof(struct node));

// Remember linkptr -> next now points to null because we are at the last node in the list so it's ok to allocate a new area of mem  to point to. 
	
        linkptr = linkptr -> next;
	
	if (linkptr == 0)	// checks to see if we are out of memory
	{
		printf("out of memory");
		return(0);
	}
	
	linkptr -> next = 0; // Set the next pointer to NULL to indicate we are at the end of our list.
	linkptr -> c = 'E';
	
	return(0);
		
	
}

Here is the code i am trying to get to work. I've just run it through GDB and the malloc line is the one giving me a problem. GDB output:
Program received signal SIGSEGV, Segmentation fault.
0x00000000004005ab in main () at ll1.c:29

If i change it to just 'linkptr' instead of 'linkptr -> next' then it works but will that not also overwrite linkptr->char that is stored?

I might be coming across as very confused so bear with me, the helpdesk guy doesn't know C so i'm pretty stuck at the moment.

Thanks

After the while loop linkptr -> next points to null (since it's the end of the list,)
hence it's fine to malloc and create some more memory as i understand it...

Could you help me out a little more?

Cheers.

It is definitely a, so linkptr is null once the while loop ends?

But does that not mean that since linkptr is null then linkptr->next it also null so it's ok to create more memory?? Or am i trying to reference a node that just doesn't exsist?

Thanks for bearing with me.

edit: And if that's the case how would i go about fixing the problem?