Question

I don’t understand why this code is worked.

int f(int,int);

int main()
{
    f(12,21);
    return 0;
}

int f(int,int b)
{
    return 0;
}

How can i use first arg in function f(…) ?

Answer 1

Parameter names are not part of the function signature, only its name and the parameters’ types are.

Therefore, it’s perfectly legal not naming your parameters. However, you can’t use them. (unless of course you do some hacking)

Some hacking: Note – not platform independent, not guaranteed by the standard, but fun 🙂

void foo (int x, int, int z)
{
   int* pz = &z;
   int y = *(--pz);
   cout << x << " " << y << " " << z;
}

int main()
{
    foo(2,3,4);
    // prints "2 3 4"
}

This works for me on Win7, with MSVS 2008. The code is dependent on how parameters are pushed on the function argument stack.

In production code, you should use names for all parameters, including in declarations, and make them as descriptive as possible.