reference vs. int arg confusion

The following C++ program compiles without warning message
under RedHat 9.4 with a recent version of g++:

// all put in file main.cpp for simplicity
#include <stdio.h>
class MyClass
   {
   public:
      void func (int);
      void func (int&);
   }

void MyClass::func (int x) { printf ("arg: %d\n", x); }
void MyClass::func (int x&) { x = 10; }

void main ()
   {
   MyClass mc;
   mc.func (33); // legal: 1st func called, 'arg: 33' is printed
   int x = 42;
// mc.func (x); // error: compiler can't tell which func to call
   }

Leaving aside the matter of whether or not the above represents
a good design (it doesn't) or is strictly legal under the
specification
(it is, as far as I can tell), the above code does in fact compile, so
g++ evidently has a way of telling these two functions apart when
the class is defined.

However, I have not been able to find a way to explicitly invoke the
1st func or the 2nd func at will with an int variable inside main.
Any ideas?

Thank you,