1) If the object is created via a pointer and that pointer is later deleted or given a new address to point to, does the object that it was pointing to call its destructor (assuming nothing else is pointing to it)? It depends on the type of pointers. For example, smart pointers often delete their … Read more
The destructor of A will run when its lifetime is over. If you want its memory to be freed and the destructor run, you have to delete it if it was allocated on the heap. If it was allocated on the stack this happens automatically (i.e. when it goes out of scope; see RAII). If … Read more
Yes. You also need to implement the destructor: class A { public: virtual ~A() = 0; }; inline A::~A() { } should suffice. If you derive anything from A and then try to delete or destroy it, A‘s destructor will eventually be called. Since it is pure and doesn’t have an implementation, undefined behavior will … Read more
Probably the real reason that pure virtual destructors are allowed is that to prohibit them would mean adding another rule to the language and there’s no need for this rule since no ill-effects can come from allowing a pure virtual destructor. Nope, plain old virtual is enough. If you create an object with default implementations … Read more
UPDATE: This question was the subject of my blog in May of 2015. Thanks for the great question! See the blog for a long list of falsehoods that people commonly believe about finalization. When should I manually create a destructor? Almost never. Typically one only creates a destructor when your class is holding on to … Read more
Basically, any time you want some other class to be responsible for the life cycle of your class’ objects, or you have reason to prevent the destruction of an object, you can make the destructor private. For instance, if you’re doing some sort of reference counting thing, you can have the object (or manager that … Read more
Throwing an exception out of a destructor is dangerous. If another exception is already propagating the application will terminate. #include <iostream> class Bad { public: // Added the noexcept(false) so the code keeps its original meaning. // Post C++11 destructors are by default `noexcept(true)` and // this will (by default) call terminate if an exception … Read more
No, destructors are called automatically in the reverse order of construction. (Base classes last). Do not call base class destructors.
I’d recommend using Python’s with statement for managing resources that need to be cleaned up. The problem with using an explicit close() statement is that you have to worry about people forgetting to call it at all or forgetting to place it in a finally block to prevent a resource leak when an exception occurs. … Read more
Because Java is a garbage collected language you cannot predict when (or even if) an object will be destroyed. Hence there is no direct equivalent of a destructor. There is an inherited method called finalize, but this is called entirely at the discretion of the garbage collector. So for classes that need to explicitly tidy … Read more