When is Manually Calling Destructors Acceptable in C ?

Manually Calling Destructors: When and When Not To

The common wisdom in software engineering is that manually calling destructors for objects is indicative of poor design. However, under certain circumstances, it may be necessary or even beneficial to explicitly invoke destruction.

Situations Warranting Manual Invocation

The primary reason for manually calling destructors is to release memory without destroying the underlying object itself. This scenario often arises when memory allocation and deallocation are handled independently from object construction and destruction. For example, in code where:

char buffer[sizeof(MyClass)];

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

In this code, the MyClass object is constructed using placement new on an existing buffer of memory. To release the object, its destructor must be called explicitly, as the memory allocated for the buffer remains.

Other Cases

Apart from the aforementioned scenario, manual destructor invocation may also be beneficial in cases where:

• The object's lifetime is explicitly controlled by the programmer.
• The object is part of a complex data structure with specific memory management requirements.
• The object is shared among multiple entities and needs to be explicitly released when not in use.

When to Avoid Manual Destructor Invocation

While manually calling destructors can be useful in certain situations, it should not become a haphazard practice throughout the codebase. It is generally recommended to utilize resource acquisition is initialization (RAII) idioms, which automatically handle object initialization and destruction to ensure proper resource management.

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