C 程序中未定义的函数引用

Question

我是 C 编程的新手。老实说，这是我第一个使用 Function 的程序。但它不起作用。谁能告诉我应该是什么问题？

// Convert freezing and boiling point of water into Fahrenheit and Kelvin

#include<stdio.h>

void calculation(int);
void freezingCalculation(void);
void boilingCalculation(void);

int main (){

int temperature, fahrenheit, kelvin;


void freezingCalculation(void){
   int temperature = 0;
    calculation(temperature);
 printf("Freezing point in Fahrenheit is %d. \n", fahrenheit);
   printf("Freezing point in Kelvin is %d. \n", kelvin);
}

void boilingCalculation(void){
    int temperature = 100;
    calculation(temperature);
    printf("Boiling point in Fahrenheit is %d. \n", fahrenheit);
    printf("Boiling point in Kelvin is %d. \n", kelvin);
}

void calculation(int temperature){
    //Temperature in fahrenheit
    fahrenheit = ((temperature * 9) / 5) + 32;

    //Temperature in Kelvin
    kelvin = temperature + 273;
}

}

Answer 1

问题是，您试图在 main() 函数内部定义函数。这在纯 C 中是不允许的。Some compiler extensions allows "nested functions", but that's not part of the standard.

这里发生的事情是，编译器看到了函数声明，但找不到函数的任何定义，因为它们不在文件范围.

您需要将函数定义移出 main() 并根据要求调用 main() 中的函数。

Answer 2

you did not call your function.

在主函数之外编写您的方法（freezingCalculation 等）并且不要忘记 return 因为您的主函数 return 类型是 integer.Like--

#include <stdio.h>
int temperature, fahrenheit, kelvin;
void calculation(int);
void freezingCalculation(void);
void boilingCalculation(void);

int main (){



    freezingCalculation();
    boilingCalculation();

    return 0;
}
void freezingCalculation(void){
   int temperature = 0;
    calculation(temperature);
 printf("Freezing point in Fahrenheit is %d. \n", fahrenheit);
   printf("Freezing point in Kelvin is %d. \n", kelvin);
}

void boilingCalculation(void){
    int temperature = 100;
    calculation(temperature);
    printf("Boiling point in Fahrenheit is %d. \n", fahrenheit);
    printf("Boiling point in Kelvin is %d. \n", kelvin);
}

void calculation(int temperature){
    //Temperature in fahrenheit
    fahrenheit = ((temperature * 9) / 5) + 32;

    //Temperature in Kelvin
    kelvin = temperature + 273;
}

C 程序中未定义的函数引用

Undefined reference to function in C program

c

nested-function