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c++destructorundefined-behaviordelete-operator

Manually calling destructor before delete

auto obj = new Object;
obj->~Object();
delete obj;

I know it's unusual, but is it defined behavior? Can it cause any surprising problems?

Solution

  • You can only do that if you replace the destroyed object pointed by obj with a new object as per:

    auto obj = new Object;
obj->~Object();

new (obj) Object();
delete obj;

    Otherwise, you invoke Undefined Behavior.

    You should understand that:

    • new calls operator new to obtain memory, then calls the provided construtor to create the object
    • delete calls the destructor of the object, then calls operator delete to "return" memory.

    EDIT: As Bo Persson pointed out, its not a good idea if you can't provide exception guarantees