Can you print anything in C++, before entering into the main function?

Question

Can you print anything in C++, before entering into the main function?

It is interview question in Bloomberg:

Answer :create a global varia

Answer 1

#include <iostream>
using namespace std;

int b() {
  cout << "before ";
  return 0;
}
static int a = b();

int main() {
  cout << "main\n";
}

Answer 2

#include <iostream>
struct X
{
   X() 
   {
       std::cout << "Hello before ";
   }
} x;

int main()
{
   std::cout << "main()";
}

This well-formed C++ program prints

Hello before main()

You see, the C++ standard guarantees that the constructors of namespace-scope variables (in this example, it's x) will be executed before main(). Therefore, if you print something in a constructor of such an object, it will be printed before main(). QED

Answer 3

Header file

class A
{
   static A* a;
public:
   A() { cout << "A" ; }
};

Implementation file:

A* A::a = new A;

Well, statics (and not only) are initialized before the call to main.

EDIT

Another one:

bool b = /*(bool)*/printf("before main");

int main()
{
   return 0;
}

Answer 4

#include <iostream>

std::ostream & o = (std::cout << "Hello\n");

int main()
{
   o << "Now main() runs.\n";
}