.h note: previous declaration of 'QueueADT' was here typedef struct { } *QueueADT;

Question

I would like to know how to solve the errors for redefinition of the typedef struct QueueADT.

error messages

gcc -std=c99 -ggdb -Wall -Wextra  -c queueADT.c
queueADT.c:22:3: error: 'QueueADT' redeclared as different kind of symbol
 }*QueueADT;
   ^
In file included from queueADT.c:9:0:
queueADT.h:23:21: note: previous declaration of 'QueueADT' was here
 typedef struct { } *QueueADT;
                     ^
queueADT.c:30:1: error: unknown type name 'QueueADT'
 QueueADT que_create( int (*cmp)(const void*a,const void*b) ) {
 ^
queueADT.c:30:10: error: conflicting types for 'que_create'
 QueueADT que_create( int (*cmp)(const void*a,const void*b) ) {
          ^
In file included from queueADT.c:9:0:
queueADT.h:44:10: note: previous declaration of 'que_create' was here
 QueueADT que_create( int (*cmp)(const void*a,const void*b) );
          ^

The .h file has a definition if not compiling which is the queueADT and que_create

#ifndef _QUEUE_IMPL_
typedef struct { } *QueueADT;
#endif

QueueADT que_create( int (*cmp)(const void*a,const void*b) );

Now I am not sure how to define the QueueADT struct and the que_create from the .c file here

#ifndef _QUEUE_IMPL_
#include "queueADT.h"
struct node {
    void* data;
    //size_t num;
    struct node *next;
}node;


typedef struct QueueADT {
    struct node *front;                     /* pointer to front of queue */
    struct node *rear;                      /* pointer to rear of queue  */
    int *contents[ QUEUE_SIZE ];      /* number of items in queue  */
    int *cmprFunc;                    /* The compare function used for insert */
}*QueueADT;






QueueADT que_create( int (*cmp)(const void*a,const void*b) ) {

    struct QueueADT *new;
    new = (struct QueueADT*)malloc(sizeof(struct QueueADT));

    if (cmp == NULL) {
        //do I create a new pointer to the cmp_int64?
        new->front = NULL;
        new->rear = NULL;
        new->cmprFunc = NULL;

    } else {
        new->cmprFunc = &cmp;
        new->front = NULL;
        new->rear = NULL;
    }

    return ( new );
}

Edit 1 Error message went from

queueADT.c:22:3: error: 'QueueADT' redeclared as different kind of symbol
 }*QueueADT;
   ^
In file included from queueADT.c:9:0:
queueADT.h:23:21: note: previous declaration of 'QueueADT' was here
 typedef struct { } *QueueADT;
                     ^
queueADT.c:30:1: error: unknown type name 'QueueADT'
 QueueADT que_create( int (*cmp)(const void*a,const void*b) ) {
 ^

To

In file included from queueADT.c:8:0:
queueADT.h:44:1: error: unknown type name 'QueueADT'
 QueueADT que_create( int (*cmp)(const void*a,const void*b) );
 ^
queueADT.h:49:19: error: unknown type name 'QueueADT'
 void que_destroy( QueueADT queue );


#define QUEUE_SIZE  5
#include "queueADT.h"
#define _QUEUE_IMPL_

struct node {
    void* data;
    //size_t num;
    struct node *next;
}node;


typedef struct QueueADT {
    struct node *front;                     /* pointer to front of queue */
    struct node *rear;                      /* pointer to rear of queue  */
    //int *contents[ QUEUE_SIZE ];      /* number of items in queue  */
    int *cmprFunc;                    /* The compare function used for insert */
}*QueueADT;


QueueADT que_create( int (*cmp)(const void*a,const void*b) ) {

    struct QueueADT *new;
    new = (struct QueueADT*)malloc(sizeof(struct QueueADT));

    if (cmp == NULL) {
        //do I create a new pointer to the cmp_int64?
        new->front = NULL;
        new->rear = NULL;
        new->cmprFunc = NULL;

    } else {
        new->cmprFunc = &cmp;
        new->front = NULL;
        new->rear = NULL;
    }

    return ( new );
}

Answer 1

The reason it wasnt finding the queueStruct was not defined as a type for QueueStruct que_crear was because they weren't being defined in the order listed below

typedef struct node {
    void* data;
    struct node *next;
}node;


struct queueStruct {
    struct node *front;                     /* pointer to front of queue */
    struct node *rear;                      /* pointer to rear of queue  */
    int *cmprFunc;
    size_t num;                             /* The compare function used for insert */
};

typedef struct queueStruct *QueueADT;

#define _QUEUE_IMPL_
#include "queueADT.h"

so @Drew I did need the single line header but it had to be defined after the struct queueStruct and before queueADT.h