How to Initialize Static Members Without Instances or Derived Classes in C ?

How to Force Initialization of a Static Member Without Instance Manipulation or Derived Class Involvement

Consider a scenario where you want to initialize a static class member when a specific class is instantiated, even without creating any instances or involving the derived class. Let's explore strategies to achieve this:

Using a Template Trick

Introducing a template trick can force static member initialization without requiring instances or altering the derived class. By creating a specialized template class called value, which takes an integer reference and its value as parameters, you can achieve the desired result.

<code class="cpp">template<typename T, T> struct value { };

template<typename T>
struct HasStatics {
  static int a; // We enforce initialization
  typedef value<int&, a> value_user;
};

template<typename T>
int HasStatics<T>::a = /* Desired side-effect */;</code>

Exploiting Syntax Ambiguity

Another approach is to leverage the ambiguity in C syntax. By using a clever combination of typedef and nested enum, you can force the initialization of multiple static members without affecting the derived class.

<code class="cpp">template<typename T, T> struct var { enum { value }; };
typedef char user;

template<typename T>
struct HasStatics {
  static int a; // We enforce initialization
  static int b; // And this one too

  // Syntax Shenanigans
  user :var<int&, a>::value,
       :var<int&, b>::value;
};

template<typename T>
int HasStatics<T>::a = /* Desired side-effect */;

template<typename T>
int HasStatics<T>::b = /* Desired side-effect */;</code>

These techniques provide efficient methods for initializing static members without the need for instance manipulation or derived class modifications.

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