How Can Type Erasure Be Achieved in C Using Virtual Functions, Function Pointers, and `shared_ptr`?

Type Erasure Techniques in C

Type erasure aims to conceal type information of a class, ensuring data safety and versatility. Various approaches exist for type erasure, each offering unique benefits and use cases. Here are a few common techniques:

1. Virtual Functions

Virtual functions provide an effective means of type erasure by defining an interface that hides implementation details. Classes adhering to this interface can be managed as a cohesive group, facilitating runtime flexibility. Boost libraries like Boost.Any and Boost.Shared_ptr employ this technique.

2. Function Pointers with Templated Functions and void*

Function pointers and templated functions allow for type erasure by storing actual objects within void* pointers. Boost.Function leverages this approach to hide the type of functors.

3. Using Shared_ptr

Shared_ptr represents a subtle yet powerful usage of type erasure. It permits the storage of arbitrary data types while ensuring appropriate destructor invocation due to the templated nature of its constructor.

Example Implementation:

int main() {
  shared_ptr<void> sp(new A); // calls A::~A() when destructed
}

Additional Usage Examples:

The example code provided in the original question demonstrates both the virtual functions and void* techniques. It showcases the use of Any_Virtual and Any_VoidPtr classes for type erasure with custom operations.

Further Reading:

• [Boost.Any Reference](https://www.boost.org/doc/libs/1_71_0/boost/any/any.hpp)
• [Boost.Function Reference](https://www.boost.org/doc/libs/1_71_0/boost/function/function_template.hpp)
• [Shared_ptr in C , Is it safe?](https://stackoverflow.com/questions/9675910/shared-ptrvoid-in-c-is-it-safe)

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