Re: previous declaration of Table was here / conflicting types for

Hi Flash Gordon:

Thanks for your reply.
The Table.c was required to be implemented as generic type.  If I am
right, Table is declared as void * in header file, the reason is that,
when used later on, it can be casted to any other type of pointers.

The implementation of Table in Table.c was defined as pointer to
struct Table, because I need to implement the members of Table.

My professor told us, void * in header indicates a generic type.
He has some sample codes where List was typedef'd void pointer but the
definition was struct List Pointer:

/* Header file List.h*/
#ifndef LIST_H
#define LIST_H

#include "bool.h"

	typedef void * List ;
	typedef void * DataL ;
	typedef void * ListIt ;

	List makeList ( int , void * (*copy)() , void (*free)() ) ;
	void freeList ( List ) ;
	void clearList ( List ) ;

	boolean accessList ( List , DataL , int ) ;
	int lengthList ( List ) ;

	boolean accessHead ( List , DataL ) ;
	boolean insertHead ( List , DataL ) ;
	boolean deleteHead ( List , DataL ) ;

     /* not all the header file is copied here*/









/* List.c */

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

#ifndef DATA
#define DATA
typedef void * Data ;
#endif

typedef struct ListNode {
	struct ListNode * next ; 	/* reference to following ListNode */
	struct ListNode * previous ;	/* reference to preceding ListNode */
	Data dptr ;
} ListNode ;

typedef struct List {
	ListNode * head ; 		/* Head end of List		*/
	ListNode * tail ;		/* Tail end of List		*/
	int _lengthList ;		/* number of items within List	*/
	int _sizeData ;			/* byte size of data to be stored */
	void (*_freeData)( ) ;		/* returns data item to heap	*/
	void * (*_copyData)( ) ;	/* copies data item to another	*/
} * List ;


Regards
Michael




On May 3, 2:32 am, Flash Gordon <s...@[EMAIL PROTECTED]
> wrote:
> Michael.Z wrote, On 03/05/08 08:22:
>
> > Anyone who can help:
>
> > Given a Table.h file I am writing a Table.c file.
> > I keep getting the compile error:
>
> > previous declaration of Table was here /  conflicting types for
>
> > I think the problem was the result of two pieces of code.
> > First:typedefstruct Table;  /* in Table.c*/
>
> This says that Table is a struct.
>
> > Second: struct Table { /*struct definition */ }  *Table;  /* in
> > Table.h */
>
> This says it is a pointer to a struct, that is what the * means.
>
> > How can I solve the problems?
>
> By not providing different definitions.
>
> > Here are the two files
>
> <snip>
>
> >typedefvoid * Table ;
>
> This is not what you said you had and is defining table as yet another
type.
>
> <snip>
>
> >typedefstruct Table{
> >     int sizeTable;
> >     unsigned sizeData;
> >     int (*diff)();
> >     unsigned (*hash)();
> >     void *(*copy)();
> >     void (*free)();
> > } * Table;
>
> This is what you said. However pointers to void and pointers to structs
> are different things for the simple reason that void and struct are
> different.
>
> Also hiding pointers behind atypedefis generally considered a bad thing.
> --
> Flash Gordon