Question

#include <iostream>
using namespace std;

typedef int MYINT;

int main() 
{ 
    int y = MYINT();                     // As expected, y = 0; value initialization
    cout << MYINT();                     // Error
    cout << sizeof(MYINT());             // Error
} 

Why the last two lines in the main function before the closing brace give error? Why is the expression MYINT() treated differently in different contexts? Any Standard reference will be helpful.

Answer 1

I do not see any error for the cout << MYINT(); line. However I see invalid application of 'sizeof' to a function type for the cout << sizeof(MYINT()); line. The problem is the () around MYINT(). The C++ standard says this about sizeof and how it is parsed:

sizeof unary-expression
sizeof ( type-id )

There is a parsing ambiguity between sizeof unary-expression and sizeof ( type-id ). It is resolved by using longer match. It parses sizeof (MYINT()) as sizeof ( type-id ), MYINT() is a function type and thus you see the error.