How to print "GeeksforGeeks" with empty main() in C, C++ and Java?

C language

1. One way of doing this is to apply GCC constructor attribute to a function so that it executes before main() (See this for details). C

   #include <stdio.h>
   
   /* Apply the constructor attribute to myStartupFun() 
      so that it is executed before main() */
   void myStartupFun(void) __attribute__((constructor));
   
   /* implementation of myStartupFun */
   void myStartupFun(void)
   {
       printf("GeeksforGeeks");
   }
   
   int main()
   {
   }
   

   Output:

   GeeksforGeeks

2. In linux, just override the default definition of _start() function so that it would work as a custom startup code. See this article to understand more. C

   #include <stdio.h>
   #include <stdlib.h>
   
   int main(void)
   {
   }
   
   // _start() function
   void _start(void)
   {
       printf("GeeeksforGeeks");
   
       // Call main() function
       int var = main();
       exit(var);
   }
   

   Now compile this by following command

   gcc -nostartfiles -o file file.c

   Output:

   GeeksforGeeks

C++ language

1. The idea is to create a class, have a cout statement in constructor and create a global object of the class. When the object is created, constructor is called and "GeeksforGeeks" is printed. CPP

   #include <iostream>
   
   class MyClass {
   public:
       MyClass()
       {
           std::cout << "GeeksforGeeks";
       }
   } m;
   
   int main()
   {
   }
   

   Output:

   GeeksforGeeks

2. The idea is to create struct and use the same logic which is discussed in above. The reason is that struct and class in C++ are exactly the same data structure except struct default to public visibility while class defaults to private visibility CPP

   #include <iostream>
   
   struct Mystruct {
   
       Mystruct()
       {
           std::cout << "GeeksforGeeks";
       }
   } obj;
   
   int main() {}
   

   Output:

   GeeksforGeeks

3. By using global variable, idea is to initialise printf() function to global variable, but it will work only in C++ language as in C language we can’t initialise variable or expression like this to global variable. CPP

   #include <cstdio>
   
   int var = printf("GeeksforGeeks");
   
   int main()
   {
   }
   

   Output:

   GeeksforGeeks

Java language

class Myjava {
    static
    {
        System.out.println("GeeksforGeeks");
    }
    public static void main(String args[])
    {
    }
}

GeeksforGeeks