Compile Time function binding in c++

01 Mar 2022 Balmiki Mandal 0

Compile Time Function Binding in C++

Compile time function binding, also known as static binding, is the process of determining which function to call at compile time. This is done by matching the function call with the function definition based on the function's name, signature, and scope.

Compile time function binding is the default binding in C++. It is fast and efficient, but it is also less flexible than dynamic binding.

Example of compile time function binding:

C++

void print(int x) {
  std::cout << x << std::endl;
}

int main() {
  print(5);
  return 0;
}

When the compiler encounters the function call print(5), it knows which function to call because there is only one function named print() with the signature void print(int).

Advantages of compile time function binding:

Fast and efficient
Easy to debug

Disadvantages of compile time function binding:

Less flexible than dynamic binding

When to use compile time function binding:

When you know which function to call at compile time
When performance is critical

Example use cases of compile time function binding:

Mathematical functions
String functions
Array functions

Dynamic binding, also known as late binding, is the process of determining which function to call at runtime. This is done by using a virtual function table (VFT). The VFT is a table that contains the addresses of all the virtual functions in a class.

Dynamic binding is achieved by declaring a function as virtual. When a virtual function is called, the compiler does not know which function to call at compile time. Instead, it generates code to look up the address of the function in the VFT at runtime.

Example of dynamic binding:

C++

class Animal {
public:
  virtual void speak() {
    std::cout << "Animal sound" << std::endl;
  }
};

class Dog : public Animal {
public:
  void speak() override {
    std::cout << "Woof!" << std::endl;
  }
};

int main() {
  Animal* animal = new Dog();
  animal->speak(); // Outputs "Woof!"
  return 0;
}

In this example, the speak() function is declared as virtual in the Animal class. This means that the compiler will use dynamic binding to determine which function to call when speak() is called.

When the speak() function is called on the animal pointer, the compiler does not know which function to call because the animal pointer could point to any type of object that inherits from Animal. Instead, the compiler generates code to look up the address of the speak() function in the VFT of the object that the animal pointer points to.

The VFT of the Dog object contains the address of the speak() function in the Dog class. This is why the speak() function in the Dog class is called when speak() is called on the animal pointer.

Advantages of dynamic binding:

More flexible than compile time binding
Allows for polymorphism

Disadvantages of dynamic binding:

Slower and less efficient than compile time binding
More difficult to debug

When to use dynamic binding:

When you do not know which function to call at compile time
When you need to use polymorphism

Example use cases of dynamic binding:

Graphical user interfaces (GUIs)
Event-driven programming
Object-oriented programming (OOP)

Conclusion

Compile time function binding and dynamic binding are two different ways to bind functions in C++. Compile time function binding is faster and more efficient, but it is less flexible than dynamic binding. Dynamic binding is more flexible, but it is slower and less efficient than compile time function binding.

The best way to choose which binding to use is to consider the specific needs of your program. If you know which function to call at compile time and performance is critical, then you should use compile time function binding. If you need to use polymorphism or do not know which function to call at compile time, then you should use dynamic binding.

Compile Time function binding in c++