Virtual Destructors and the Absence of Virtual Constructors in C++: Analysis and Examples

Key words: polymorphism, memory leak, memory management, smart pointers, std::shared_ptr, virtual function table (vtable) C++ is a powerful programming language extensively utilized in both system and application programming; particularly in scenarios where performance and resource control are critical. A key aspect of C++ is its memory and resource management, especially in the context of inheritance and polymorphism. This article provides an in-depth analysis of the use of virtual destructors and explains why constructors cannot be virtual in C++. Code examples illustrate common mistakes arising from improper destructor usage and demonstrate correct implementation approaches. Virtual destructors are essential in polymorphic class hierarchies for proper resource deallocation and prevention of memory leaks. In contrast, constructors cannot be virtual due to the specific mechanics of object initialization and the functioning of the virtual table (vtable). The article also explores modern memory management tools, such as smart pointers (std::shared_ptr, std::uniqueptr), and their role in ensuring safe and efficient resource management within polymorphic contexts. This material is meant for the developers seeking to deepen their understanding of memory management in C++, particularly in complex polymorphic hierarchies.