在一个声明语句中定义函数和变量

Question

I am pretty sure the following is legal

int a, *b, c[5], d(char x);

This defines an integer a , a pointer to int b , an array of 5 ints c , and declares a function d taking a char and returning int.

Is it legal to provide the definition of the function there as well? (provided we're not in function scope)

int a, f()
{
   return 1;
}

int main()
{
    cout << a << f(); //prints 01;
}

MSVC rejects the code. If it's right to do so, I am wondering which rule in the standard allows such function declarations but not definitions.

I am trying to do a codegolf-style challenge and I need to minimize my code in terms of characters and I was wondering if this trick is legal C++.

Answer 1

No, a function definition only has a single declarator. It's specified in C++11 8.4.1 and A.7:

function-definition:
    attribute-specifier-seq<opt> decl-specifier-seq<opt> declarator virt-specifier-seq<opt> function-body

Answer 2

int a, *b, c[5], d(char x);

Is valid because the compiler knows you will not declare any variables anymore. The compiler knows this because there is a semicolon standing behind the statement.

int a, f()
{
return 1;
}

Is in valid because the compiler doesn't know when you are declaring the variable and the function. And when you start the implemantation of the function;(It thinks you want to declare everything from the int to the first semicolon after return 1 as a variable).