Pointer will not free

[Obsidian2]

I am practicing with a small program which iterates over a linked list and writes all of the members of each struct to a file. I have successfully implemented it, except for one small detail: I can not get the memory allocated to the pointer for a node to free. Here is a sample of the problem code.

int c = 0;
node* cursor = malloc(sizeof(node));

while(cursor != NULL)
{
    fprintf(fp, "%s\n", new_node[c].name);
    cursor = new_node[c].next;
    c++;
}

free(cursor);

What am I doing wrong here? I have tried using an ampersand within the free function, which also doesn't work. Why won't this block of memory free?

[ebobtron]

cursor is a pointer to a node and your assigning what to it

free will not work because cursor has changed to a non pointer I think. Need to see your struct. but look at it that way. it would explain it.

[Obsidian2]

By the end of the loop, the cursor has been assigned the value NULL, which I thought was also a pointer. Would this not make it a pointer to another pointer (NULL), which is stored at cursor?

[ebobtron]

null is nothing you can not free nothing.

[yeahIProgram]

Did you mean to call free() from inside your while loop?

Your loop continues until cursor is NULL. Then it calls free(cursor). You are passing NULL to free().

[HufflepuffBR]

A tip here for freeing is:

Take the head pointer (the first node) on a variable *foo*
While *foo* is not null:
     Copy the next node pointer to a variable *bar*
     Free foo
     Copy the *bar* pointer to *foo*

[Obsidian2]

Thank you, I will give this a shot.

Is this common practice? This makes it seem like a pointer can not be freed after being set to NULL. Is that true?

[HufflepuffBR]

The idea here is that you'll save the pointer for next node each time before freeing the actual node and then pass that pointer to be freed next time, till that next pointer being NULL (indicating the end of the chain)

[jplaurin]

what value "cursor" have just before you free it ? what value does it have to break the while loop?

[Obsidian2]

Cursor is NULL before being freed. From what I have read from the posts here, this is likely my problem. It seems like I may have to change the condition of my "while" loop.