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Also note the virtual destructors in the base classes, B1 and B2. They are necessary to ensure delete d can free up memory not just for D, but also for B1 and B2, if d is a pointer or reference to the types B1 or B2. They were excluded from the memory layouts to keep the example simple. [nb 2]
Virtual functions allow a program to call methods that don't necessarily even exist at the moment the code is compiled. [citation needed] In C++, virtual methods are declared by prepending the virtual keyword to the function's declaration in the base class. This modifier is inherited by all implementations of that method in derived classes ...
To elaborate on the above example, consider a base class with no virtual functions. Whenever the base class calls another member function, it will always call its own base class functions. When we derive a class from this base class, we inherit all the member variables and member functions that were not overridden (no constructors or destructors).
The destructor has the same name as the class, but with a tilde (~) before it. [2] For example, a class called foo will have the destructor ~ foo (). Additionally, destructors have neither parameters nor return types. [2] As stated above, a destructor for an object is called whenever the object's lifetime ends. [2]
Virtual inheritance is a C++ technique that ensures only one copy of a base class ' s member variables are inherited by grandchild derived classes. Without virtual inheritance, if two classes B and C inherit from a class A , and a class D inherits from both B and C , then D will contain two copies of A ' s member variables: one via B , and one ...
For example, the compiler generated destructor will destroy each sub-object (base class or member) of the object. The compiler generated functions will be public , non- virtual [ 3 ] and the copy constructor and assignment operators will receive const& parameters (and not be of the alternative legal forms ).
The C++ language does allow a program to call a destructor directly, and, since it is not possible to destroy the object using a delete expression, that is how one destroys an object that was constructed via a pointer placement new expression. For example: [11] [12]
In computer programming, run-time type information or run-time type identification (RTTI) [1] is a feature of some programming languages (such as C++, [2] Object Pascal, and Ada [3]) that exposes information about an object's data type at runtime. Run-time type information may be available for all types or only to types that explicitly have it ...