c中用于用户定义函数的未解析外部符号-解网

问：

我对编程非常陌生，在我的课程中，我们学习 C 语言，所以请怜悯我写得不好的代码，编译器会因为错误而无法运行程序，所以我很难确定出了什么问题。回到主要问题，我得到未解决的外部符号......在function_main中引用，我真的不知道我在哪里搞砸了

#include<stdio.h>
char DisplayMenu(void);
void ViewBooks();
void SearchBookPrice();
void UpdateBookPrice();


int main()
{
    char userchoice;
    int bookID[5] = { 200,230,500,540,700 };
    char bookTitle[5][50] = { {"Using Information Technology 12th Edition" }, { "Beyond HTML" },{"Build Your Own PC"},{"Instant Java Servlets"},{"DIgital Image: A Practical Guide"} };
    float bookPrice[5] = { 100.30,50.40,47,83.30,22.90 };

    do
    {
        userchoice = DisplayMenu();
        if (userchoice == 'V')
            ViewBooks();
        else if (userchoice == 'S')
            SearchBookPrice();
        else if (userchoice == 'U')
            UpdateBookPrice();
    } while (userchoice != 'E');

    printf("Thank you for using our system. Have a nice day!\n");

    return 0;
}

char DisplayMenu(void)
{
    char choice;

    printf("*************************************************************************\n");
    printf("V:View Books  S:Search Book Price  U:Update Book Price  E:Exit");
    printf("*************************************************************************\n");
 
    do
    {
        printf("Enter your choice: ");
        scanf(" %c", &choice);

        if (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E')
            printf("Invalid Choice\n");

    } while (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E');
    

    return choice;
}

void ViewBooks(int bookID[],float bookPrice[])
{
    printf("%d   Using Information Technology 12th Edition   $%f\n", bookID[0], bookPrice[0]);
    printf("%d   Beyond HTML   $%f\n", bookID[1], bookPrice[1]);
    printf("%d   Build Your Own PC   $%f\n", bookID[2], bookPrice[2]);
    printf("%d   Instant Java Servlets  $%f\n", bookID[3], bookPrice[3]);
    printf("%d   Digital Image: A Pratical Guide  $%f\n", bookID[4], bookPrice[4]);

    return;
}

void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5])
{
    int idsearch, i= 0, match = -1;
    printf("*************************************************************************\n");
    printf("Search by book ID\n");
    printf("*************************************************************************\n");

    printf("Enter book ID: ");
    scanf("%d", &idsearch);

    while (i<5 && match==-1)
    {
        if (bookID[i] == idsearch)
            match = i;
        i++;
    }



    if (match == -1)
        printf("Please refer to the customer service for assitance");
    else
    {
        printf("The book id is : %d\n", &idsearch);
        printf("The price of %s is %f", bookTitle[match], bookPrice[match]);
    }

    return;

}

void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5])
{
    int idsearch, i = 0, match = -1;
    printf("Enter book ID: ");
    scanf("%d", &idsearch);
    while (i < 5 && match == -1)
    {
        if (bookID[i] == idsearch)
            match = i;
        i++;
    }
    if (match == -1)
        printf("The book ID is not found. Please make sure the book ID is correct");
    else
    {
        printf("Current book price is %f\n", bookPrice[match]);
        printf("Enter new price for (%d-%s): ", bookID[match], bookTitle[match]);
        scanf("%f", &bookPrice[match]);
    }
    return;
}

C 函数未解析 - 外部

使用 C 编译器，它对我来说编译得很好。使用 C++ 编译器时，存在未解析的符号，因为您的前向声明和对的调用不包含参数，这些参数是 C++ 中函数签名的一部分。它试图调用一个不带参数的版本，但你只提供了需要参数的版本。ViewBookSearchBookPriceUpdateBookPrice

1赞 Weather Vane 6/19/2021

如果 C 编译器没有警告错误，则应提高警告级别。不过，可执行代码确实链接了，没有任何未解析的外部符号。printf("The book id is : %d\n", &idsearch);

1赞 HAL9000 6/19/2021

如果你声明一个struct book { .... };

答：

0赞 Denis Turgenev 6/19/2021 #1

函数声明与函数体不匹配。

这是工作代码。

#include<stdio.h>
char DisplayMenu(void);
void ViewBooks(int bookID[],float bookPrice[]);
void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5]);
void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5]);


int main()
{
    char userchoice;
    int bookID[5] = { 200,230,500,540,700 };
    char bookTitle[5][50] = { {"Using Information Technology 12th Edition" }, { "Beyond HTML" },{"Build Your Own PC"},{"Instant Java Servlets"},{"DIgital Image: A Practical Guide"} };
    float bookPrice[5] = { 100.30,50.40,47,83.30,22.90 };

    do
    {
        userchoice = DisplayMenu();
        if (userchoice == 'V')
            ViewBooks(bookID, bookPrice);
        else if (userchoice == 'S')
            SearchBookPrice(bookID, bookTitle, bookPrice);
        else if (userchoice == 'U')
            UpdateBookPrice(bookID, bookTitle, bookPrice);
    } while (userchoice != 'E');

    printf("Thank you for using our system. Have a nice day!\n");

    return 0;
}

char DisplayMenu(void)
{
    char choice;

    printf("*************************************************************************\n");
    printf("V:View Books  S:Search Book Price  U:Update Book Price  E:Exit");
    printf("*************************************************************************\n");
 
    do
    {
        printf("Enter your choice: ");
        scanf(" %c", &choice);

        if (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E')
            printf("Invalid Choice\n");

    } while (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E');
    

    return choice;
}

void ViewBooks(int bookID[],float bookPrice[])
{
    printf("%d   Using Information Technology 12th Edition   $%f\n", bookID[0], bookPrice[0]);
    printf("%d   Beyond HTML   $%f\n", bookID[1], bookPrice[1]);
    printf("%d   Build Your Own PC   $%f\n", bookID[2], bookPrice[2]);
    printf("%d   Instant Java Servlets  $%f\n", bookID[3], bookPrice[3]);
    printf("%d   Digital Image: A Pratical Guide  $%f\n", bookID[4], bookPrice[4]);

    return;
}

void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5])
{
    int idsearch, i= 0, match = -1;
    printf("*************************************************************************\n");
    printf("Search by book ID\n");
    printf("*************************************************************************\n");

    printf("Enter book ID: ");
    scanf("%d", &idsearch);

    while (i<5 && match==-1)
    {
        if (bookID[i] == idsearch)
            match = i;
        i++;
    }



    if (match == -1)
        printf("Please refer to the customer service for assitance");
    else
    {
        printf("The book id is : %d\n", &idsearch);
        printf("The price of %s is %f", bookTitle[match], bookPrice[match]);
    }

    return;

}

void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5])
{
    int idsearch, i = 0, match = -1;
    printf("Enter book ID: ");
    scanf("%d", &idsearch);
    while (i < 5 && match == -1)
    {
        if (bookID[i] == idsearch)
            match = i;
        i++;
    }
    if (match == -1)
        printf("The book ID is not found. Please make sure the book ID is correct");
    else
    {
        printf("Current book price is %f\n", bookPrice[match]);
        printf("Enter new price for (%d-%s): ", bookID[match], bookTitle[match]);
        scanf("%f", &bookPrice[match]);
    }
    return;
}

这个答案没有干净地编译！除其他事项外：“Untitled2.c：87：35：警告：格式'%d'需要类型为'int'的参数，但参数2的类型为'int *' [-Wformat=]”以及有关值更改的几个警告，因为：正在尝试使用值初始化数组。注意：浮点值的尾随如下：float bookPrice[5] = { 100.30,50.40,47,83.30,22.90 };floatdoublef100.30f

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c中用于用户定义函数的未解析外部符号

Unresolved external symbol in c for user-define function

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