Why Can We Delete a Pointer to a Constant Object (T const*) in C ?

Deleting a Pointer to Const (T const*)

Why is it possible to delete a pointer to a constant object (const T* p) using "delete p", even though the destructor is a non-const member function?

Explanation

The reason for allowing the deletion of a pointer to const is primarily to support the use of const objects in dynamic memory management. Consider the following scenario:

<code class="cpp">// dynamically create object that cannot be changed
const Foo * f = new Foo;

// use const member functions here

// delete it
delete f;</code>

In this example, the object pointed to by "f" cannot be modified due to its const designation. However, the destructor of "Foo" is still required to be called upon the deletion of this object. Allowing "delete" to be used on const pointers ensures that the destructor will be invoked, ensuring proper cleanup.

It's important to note that this behavior extends beyond dynamically created objects. Even for objects defined in local scopes, destructors must be called when the scope is exited, regardless of the constness of the object. For example:

<code class="cpp">{
 const Foo f;
 // use it
} // destructor called here</code>

If destructors were not allowed to be called on const objects, it would be impossible to use const objects effectively. Therefore, the ability to delete pointers to const is crucial for maintaining the integrity of the language and its object-oriented principles.

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