A simple example demonstrating how to print "Hello World" before the main() function is called.

test_cpp_print_before_main.cpp

/** Example showing how to print "Hello World" before main().
 * Expected output:
 *   Hello World
 *   Hello from main()
 *
 * Compile with:
 *   g++ -Wall test_cpp_print_before_main.cpp -o test_cpp_print_before_main
 */


#include <iostream>


using namespace std;




/// A simple class that prints "Hello World" when constructed.
class HelloWorld
{
public:
  HelloWorld(void)
  {
    cout << "Hello World" << endl;
  }
};




// Construct a const instance,
// will call constructor before main() is entered.
const HelloWorld hello_world = HelloWorld();




int main(int argc, const char* argv[])
{
  cout << "Hello from main()" << endl;
}