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The default form of dispatch is static. To get dynamic dispatch the programmer must declare a method as virtual. C++ compilers typically implement dynamic dispatch with a data structure called a virtual function table (vtable) that defines the name-to-implementation mapping for a given class as a set of member function pointers. This is purely ...
Thus, fetching the method's address from a given offset into a virtual method table will get the method corresponding to the object's actual class. [2] The C++ standards do not mandate exactly how dynamic dispatch must be implemented, but compilers generally use minor variations on the same basic model.
As of 2021, C++ natively supports only single dispatch, though adding multi-methods (multiple dispatch) was proposed by Bjarne Stroustrup (and collaborators) in 2007. [20] The methods of working around this limit are analogous: use either the visitor pattern, dynamic cast or a library:
The call is therefore subject to all the usual additional performance costs that are associated with dynamic resolution of calls, usually more than in a language supporting only single method dispatch. In C++, for example, a dynamic function call is usually resolved by a single offset calculation - which is possible because the compiler knows ...
In computing, late binding or dynamic linkage [1] —though not an identical process to dynamically linking imported code libraries—is a computer programming mechanism in which the method being called upon an object, or the function being called with arguments, is looked up by name at runtime.
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 ...
Dynamic binding (or late binding or virtual binding) is name binding performed as the program is running. [2] An example of a static binding is a direct C function call: the function referenced by the identifier cannot change at runtime. An example of dynamic binding is dynamic dispatch, as in a C++ virtual method call.
In computer science, a dispatch table is a table of pointers or memory addresses to functions or methods. [1] Use of such a table is a common technique when implementing late binding in object-oriented programming .