Hello,
I'm trying to learn about linked lists. What is wrong here?
----------------------------------------Code:typedef struct node { NODE *pNext; } NODE;
Here is my complete example program:
Code:typedef struct node { NODE *pNext; } NODE; void doSomething(NODE *); int main(int argc, char *argv[]) { NODE *ppp; ppp = (NODE *) malloc(sizeof(NODE)); doSomething(ppp); } void doSomething(NODE *pnode) { pnode->pNext = pnode; }
Many thanks for your help!
The declaration for NODE is not known until after you attempt to use it.Originally Posted by cdave
Or...Code:typedef struct node { struct node *pNext; } NODE;Code:typedef struct node NODE; struct node { NODE *pNext; };
Last edited by Dave_Sinkula; 04-24-2005 at 08:04 PM.
7. It is easier to write an incorrect program than understand a correct one.
40. There are two ways to write error-free programs; only the third one works.*
Ah! Thanks Dave! It works!
And there it is on p.128 of "The C Programming Language (2ndEd)":
"A struct declaration defines a type."
A type. type type type!
Now it make sense. Thanks!
No, I'm still confused.
Why does this work:
but this does not work:Code:typedef struct node NODE; struct node { NODE *pNext; };
Both have a 1st typedef which depends on the 2nd type definition.Code:typedef NNN XXX; typedef int NNN;
Your help IS appreciated.
Last edited by cdave; 04-24-2005 at 08:39 PM.
The first declares a typedef for an incomplete struct type which is later defined; the second does not.
7. It is easier to write an incorrect program than understand a correct one.
40. There are two ways to write error-free programs; only the third one works.*
Yes, but why?
Why is it OK in the 1st case to declare a typdef for an incomplete type,
but in the 2nd case it is illegal to declare a typedef for an incomplete type?
Declaring struct node tells the compiler that a certain structure will exist. It doesn't know it's size or other details yet, but pointers to it could be made, for example, because the compiler knows how to handle pointers to structures. It is an incomplete type that may be completed later.
An NNN is not an incomplete type; it is not a type that the compiler understands.
7. It is easier to write an incorrect program than understand a correct one.
40. There are two ways to write error-free programs; only the third one works.*
Dave, thanks for your help, it is appreciated, especially how quickly
you responded.
I'm still confused about these type definitions, but I'm going to move
on for now.
You helped me over a hump. Thanks!
(I now think my confusion is legitimate; it's C and not me)
Last edited by cdave; 04-25-2005 at 08:23 PM.
