When Is It Okay to Manually Call Destructors?

Calling Destructors Manually: When It's Necessary or Impractical

Conventional wisdom suggests that manually invoking a destructor is a design flaw. However, there are exceptions where this approach becomes unavoidable or advantageous.

Situations Requiring Manual Destruction

Explicit destructor calls may be necessary when:

• Memory is managed separately: When memory allocation and deallocation are handled independently of object construction and destruction. Objects are created using placement new on pre-allocated memory, and their destructors are called to release the objects without freeing the memory.
• Standard allocator and vectors: Using std::vector with the default std::allocator creates this situation. Elements are constructed during push_back, but memory is pre-allocated in chunks. vector::erase destroys elements but may not release the memory.

Examples

Custom Memory Management:

char buffer[sizeof(MyClass)];

{
    MyClass* p = new(buffer)MyClass;
    p->dosomething();
    p->~MyClass();
}

Specific Design Requirements:

In certain cases, specific classes may be designed to handle memory management internally, necessitating manual destruction.

Conclusion

While manual destructor calls may be considered a design transgression in strict OOP terms, they can be strategically employed in situations where memory management is handled separately or when it is impractical or impossible to avoid their use. Such cases should be isolated and handled consistently within designated portions of the code.

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