不兼容的返回類型

Question

我有一個問題不兼容的返回類型錯誤是什麼意思？我不斷收到一個錯誤，說這個，我改變了我的代碼多次，什麼也沒有。任何人都可以幫助我，謝謝。

即時得到錯誤的：

circular_list.c: In function ‘circ_list_iterator’: 
circular_list.c:116:(return lst ? NEXT(lst) : NULL;)error: incompatible types in return 
circular_list.c:118:(return (lastreturn == lst) ? NULL : NEXT(lastreturn);)error: incompatible types in return 
circular_list.c:119:(})warning: control reaches end of non-void function 
circular_list.c: In function ‘circ_length’: 
circular_list.c:127:(while((lastreturn = circ_list_iterator(lst, lastreturn)) != NULL))error: incompatible types in assignment 
circular_list.c: In function ‘nth_node’: 
circular_list.c:136:(return NULL;)error: incompatible types in return 
circular_list.c:138:(return lst;)error: incompatible types in return 
circular_list.c:145:(return (number != 0) ? NULL : tmp;)error: incompatible types in return 

circular_list.c

#include <stdio.h> 
#include <stdlib.h> 
#include "globals.h" 
#include "circular_list.h" 

typedef struct node *list_rep; 

typedef struct node { 
    generic_ptr datapointer; 
    list_rep next; 
} node; 


#define DATA(lst) (((list_rep) (lst))->datapointer) 
#define NEXT(lst) (((list_rep) (lst))->next) 

#define TOLIST(list_rep) ((list) (list_rep)) 
#define TOREP(lst)  ((list_rep)(lst)) 

#define TOLISTPTR(list_rep_ptr) ((list *) (list_rep_ptr)) 
#define TOREPPTR(lst_ptr)  ((list_rep *)(lst_ptr)) 

static status allocate_node (list_rep *p_lst, generic_ptr data) 
{ 
    list lst = (list) malloc(sizeof(node)); 

    if (lst == NULL) 
      return ERROR; 

    *p_lst = lst; 
    DATA(lst) = data; 
    NEXT(lst) = NULL; 

    return OK; 
} 

static void free_node (list *p_lst) 
{ 
    free(*p_lst); 
    *p_lst = NULL; 

extern status init_circ_list (list *p_lst) 
{ 
    *p_lst = NULL; 
    return OK; 
} 
extern bool empty_circ_list (list lst) 
{ 
    return (lst == NULL) ? TRUE : FALSE; 
} 

status circ_insert (list *p_lst, generic_ptr data) 
{ 
    list_rep lst, *p_lst_rep = TOREPPTR(p_lst); 

    if (allocate_node(&lst, data) == ERROR) 
      return ERROR; 

    if (empty_circ_list(*p_lst)) { 
      NEXT(lst) = lst; 
      *p_lst_rep = lst; 
    } else { 
      NEXT(lst) = NEXT(*p_lst_rep); 
      NEXT(*p_lst_rep) = lst; 
    } 
    return OK; 
} 

status circ_length  (list lst) 
{ 
    list lastreturn; 
    int length; 

    length = 0; 
    lastreturn = NULL; 
    while((lastreturn = circ_list_iterator(lst, lastreturn)) != NULL) 
      length++; 
    return length; 
} 
status nth_node  (list lst, int number) 
{ 
    list tmp; 

    if (empty_circ_list(lst) == TRUE) 
      return NULL; 
    if (number == -1) 
      return lst; 

    tmp = lst; 
    do { 
      tmp = NEXT(tmp); 
      number--; 
    } while (number > 0 && tmp != lst); 
    return (number != 0) ? NULL : tmp; 

    return 0; 
} 
status circ_traverse (list lst, status  (*p_func_f)()) 
{ 
    list tmp; 

    if (empty_circ_list(lst) == TRUE) 
      return OK; 

    tmp = lst; 
    do { 
      tmp = NEXT(tmp); 
      if ((*p_func_f)(DATA(tmp)) == ERROR) 
        return ERROR; 
    } while (tmp != lst) ; 
return OK; 
} 

circular_list.h

#include "globals.h" 

#ifndef _CIRCULAR_LIST_H 
#define _CIRCULAR_LIST_H 

typedef list lastreturn; 
ABSTRACT_TYPE(list); 

extern status init_circ_list (list *p_lst); 
extern bool empty_circ_list (list lst); 
extern status circ_insert  (list *p_lst, generic_ptr data); 
extern status circ_append  (list *p_lst, generic_ptr data); 
extern status circ_delete  (list *p_lst, generic_ptr *p_data); 
extern status circ_delete_node(list *p_lst, list node); 
extern status circ_list_iterator (list lst, list lastreturn); 
extern status circ_length  (list lst); 
extern status nth_node   (list lst, int number); 
extern status circ_traverse  (list lst, status  (*p_func_f)()); 

extern generic_ptr circ_head(list lst); 
extern list   circ_tail(list lst); 

#endif 

globals.h

#ifndef _GLOBALS_H 
#define _GLOBALS_H 

typedef enum {OK, ERROR} status; 
typedef enum {FALSE = 0, TRUE = 1} bool; 

typedef void *generic_ptr; 

typedef unsigned char byte; 

#define ABSTRACT_TYPE(t)  
typedef void *(t) 

#endif 

Answer 1

這看起來錯：

status nth_node(list lst, int number) 
{ 
    list tmp; 

    ... 

    return (number != 0) ? NULL : tmp; 

    ... 
} 

tmp不是status。