c - 编译C程序时 undefined symbol

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已关闭。这个问题是 not reproducible or was caused by typos 。目前不接受答案。

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这个问题是由拼写错误或无法再重现的问题引起的。虽然类似的问题可能是 on-topic在这里，这个问题的解决方式不太可能帮助 future 的读者。

已关闭 6 年前。

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编译下面的源代码时出现以下错误，我不明白为什么。你能解释一下我做错了什么吗？我在使用失败方法之前已经定义了它的签名，但是链接器找不到该符号。

Undefined symbols for architecture x86_64:
  "_numberOfDays", referenced from:
      _main in determinetomorrow-240382.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

#include <stdio.h>
#include <stdbool.h>

struct Date
{
    int month;
    int day;
    int year;
};

int numberOfDays(struct Date);
bool isLeapYear(struct Date);

int main (void) {


    struct Date today, tomorrow;
    printf("Enter todays date int format (mm dd yyyy): ");
    scanf("%i%i%i", &today.month, &today.day, &today.year);

    if(today.day != numberOfDays(today)) {
        tomorrow.day = 1;
        tomorrow.month = 1;
        tomorrow.year = today.year + 1;
    } else if(today.month == 12) {
        tomorrow.day = 1;
        tomorrow.month = today.month + 1;
        tomorrow.year = today.year + 1;
    } else {
        tomorrow.day = 1;
        tomorrow.month = today.month + 1;
        tomorrow.year = today.year;
    }

    printf("Tomorrow's date is %i/%i/%.2i. \n", tomorrow.month, tomorrow.day, tomorrow.year % 100);

    return 0;
}

int numberOfDay(struct Date d) {
    int days;
    const int daysPerMonth[12] = 
        {31,28,31,30,31,30,31,31,30,31,30,31};
    if(isLeapYear(d) == true && d.month == 2)
        days = 29;
    else
        days = daysPerMonth[d.month - 1];

    return days;
}

bool isLeapYear(struct Date d) {
    bool leapYearFlag;

    if((d.year % 4 == 0 && d.year % 100 != 0) || d.year % 400 == 0)
        leapYearFlag = true;
    else
        leapYearFlag = false;

    return leapYearFlag;
}

Answer 1

int numberOfDays(struct Date);

int numberOfDay(struct Date d) {
    int days;
    const int daysPerMonth[12] = 
        {31,28,31,30,31,30,31,31,30,31,30,31};
    if(isLeapYear(d) == true && d.month == 2)
        days = 29;
    else
        days = daysPerMonth[d.month - 1];

    return days;
}

您的函数名称有拼写错误。