当返回值的类型与声明的返回类型不同时，返回值会怎样？

Question

Why is my simple C program printing "hello world" and being compiled with no errors and is running fine when I gave a floating point number next to return statement? Shouldn't it be an error to do so?

Here is my code:

#include<stdio.h>
int main()
{
    printf("hello world");
    return 2.1;
}

Answer 1

When you return a different type from the declared type of the function, the value is automatically converted to the declared type. So it's equivalent to doing:

return (int) 2.1;

Answer 2

For the same reason of

int main(void)
{
    // ...
    int x = 2.1;

    // ...
   return x;
}

This is called implicit conversion .

Answer 3

The return code will be casted automatically on return. The long version is

return (int) 2.1;

Answer 4

您的代码将返回一个整数，因为编译器将负责将float转换为整数。

Answer 5

This is normal as the value well be implicitly converted to your declared type. the compiler will not mind but you'll get unexpected results at the runtime in general and in this specific case the casting to (int).