How do i fix this error? warning: implicit declaration of function ‘main_menu’

Question

this is a b-day reminder code utilizing linkedlists

typedef struct node  
{  
    char name[61];  
    int month;          int day;  
    int year;  
    struct node *next;  
}node;  

this is the list

typedef struct list  
{  
    node *head;  
    node *tail;  
}list;  

this is the create list code

list *create_list(list *plist)  
{  
    plist->head = NULL;  
    plist->tail = NULL;  
    return plist;  
}  

this inserts the node created to the list

list *insert_list(list *plist, node *pnode, node *new_node)  
{  
    new_node->next = pnode->next;  
    pnode->next = new_node;  
    if (plist->tail == pnode)  
    {  
            plist->tail = new_node;  
    }  
}  

this is the add birthday menu

void add_birthday(list *List)  
{  
    char x;  
    node *data = (node *) malloc(sizeof(node));  
    List = (list*) malloc(sizeof(list));  
    printf("******************************************************************\n");  
    printf("                    ADD BIRTHDAY REMINDER FORM\n");  
    printf("******************************************************************\n");  
    List = insert_list(List, data, create_node(data));  
    printf("Would you like to add another(y/n)?\n");  
    scanf("%c", &x);  
    if (x=='y')  
    {  
            while (x=='y')  
            {  
                    if (x=='y')  
                    {  
                            getchar();  
                            printf("******************************************************************\n");  
                            node *data = (node *) malloc(sizeof(node));  
                            List = insert_list(List, data, create_node(data));  
                            printf("Would you like to add another(y/n)?\n");  
                            scanf("%c", &x);  
                    }  
            }  
    }
    main_menu(List);  //the problem lies here
}  

this is the main menu

void main_menu(list* List)  
{  
    int x;  
    printf("Welcome to myCalendar version 1.0.0\n");  
    printf("Please input the number that you wish to do:\n");  
    printf("[1] Add Birthday Reminder\n");  
    printf("[2] Delete Birthday Reminder\n");  
    printf("[3] View Calendar\n");  
    printf("[4] Quit\n");  
    scanf("%d", &x);  
    getchar();  
    switch (x)  
    {  
            case 1:  
                    add_birthday(List);  
                    break;  
            case 2:  
                    delete_reminder(List);  
                    break;  
            case 3:  
                    view_calendar(List);  
                    break;  
            case 4:  
                    free(List);  
                    break;  
        }  
}

this is the main

int main(void)  
{  
    list* List = (list*) malloc(sizeof(list));  
    List = create_list(List);  
    main_menu(List);  
    return 0;  
}  

Answer 1

Is the definition of main_menu() is after add_birthday() ? If yes define main_menu() before add_birthday() . Also define all the methods before main() or atleast declare them before main() .

Answer 2

您没有将包含main.menu（）声明的* .h包含在包含main（）或add_birthday（）的* .c中，也没有将错误指向任何地方。

Answer 3

Have you declared main_menu? In the absence of declaration a function is assumed to return 'int'. But, you function definition says, it is returning void. This is the cause of all the confusion.