Dynamic_cast vs. static_cast in C : What's the Difference and When Should I Use Each?

Understanding dynamic_cast versus static_cast in C

Dynamic Runtime Type Checking

dynamic_cast is a powerful C operator used to perform dynamic runtime type checking and casting. It allows you to convert a pointer or reference from one type to another at runtime. The cast is successful if the object pointed to is indeed of the target type; otherwise, it returns a null pointer or reference.

Static Compile-Time Type Checking

static_cast is a compile-time cast operator that forces a conversion from one type to another. It does not perform runtime type checking. If the types are not compatible, static_cast will generate a compiler error. However, it is more efficient than dynamic_cast as it occurs at compile time rather than runtime.

C Equivalent of dynamic_cast

To understand dynamic_cast better, let's consider how we can implement its functionality in C. In C, we can use a combination of void pointers and function pointers to achieve a similar effect. Here's a simplified example:

// Base class pointer
void* base_ptr = ...;

// Check if the object pointed to by 'base_ptr' is of type 'Derived'
if (strcmp(((Derived*)base_ptr)->vtable->name, "Derived") == 0) {
    // Cast to 'Derived*' using a function pointer
    Derived* derived_ptr = base_ptr;
} else {
    // Handle the case where the object is not of the expected type
}

Here, we examine the virtual function table (vtable) of the object to determine its actual type. If it matches the target type, we perform the cast using a function pointer. While this approach is not as robust or versatile as dynamic_cast in C , it provides a more static type checking capability in C.

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