c - : main(){}, int main(){} 和 int main(void){} 有什么区别

Question

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What should main() return in C and C++? (19 个回答)

Why is the type of the main function in C and c++ left to the user to define? [duplicate] (6 个回答)

已关闭 9 年前。

我目前正在学习C，写过很多小程序。但是，我注意到主函数可以这样开始:

    main()
    {
       //code
    }

或

    int main()
    {
      //code
      return 0;
    }

或

    int main(void)
    {
       //code
       return 0;
    }

我应该使用哪个选项？谢谢!

Answer 1

对于标准 C

For a hosted environment (that's the normal one), the C99 standard says:

5.1.2.2.1 Program startup

The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:

int main(void) { /* ... */ }

or with two parameters (referred to here as argc and argv, though any names may be used, as they are local to the function in which they are declared):

int main(int argc, char *argv[]) { /* ... */ }

or equivalent;⁹⁾ or in some other implementation-defined manner.

⁹⁾ Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char **argv, and so on.

这(在 C89 中有效)main()隐含的意思是(以前)int main(void) 。然而，默认返回类型规则在C99中已被放弃。另外:

main()意味着 - 一个函数 main接受未指定数量的参数。

main(void)表示“一个函数 main 不带参数。