How to forbid the use of the default constructor in C++?

Question

I don't want to make it possible in my program to create an object without passing arguments to the constructor.

Is there a way?

Answer 1

While the other answers are true, there is a new technique in C++11 for expressing that : deleted default constructor

It allows forbidding a function without depending on any other trick. It also clearly express your intention in the code.

class X {  public:     X(int) {}     X() = delete; // will never be generated };  int main() {      X x; // will not compile;     X y(1); // will compile.     return 0; } 

Answer 2

When you declare any other constructor, the compiler will not generate the default constructor for you. If you have specified a default no-argument constructor, you can make it private.

Remember that the compiler can automatically generate each of these 4 member functions for a class.

• default no argument constructor
• default destructor
• copy constructor
• assignment operator

But it will not generate a default one if you have declared one yourself, i.e., if you declared a constructor yourself, it will not create the default constructor. If you didn't declare any of the other 3 though, the compiler can generate them.

edit: Note that this information applies to C++03, but it is different in C++11 as Matthieu M. mentions in the comments. C++11 also allows for the constructor to be explicitly forbidden. See Offirmo's answer.