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Although function pointers in C and C++ can be implemented as simple addresses, so that typically sizeof(Fx)==sizeof(void *), member pointers in C++ are sometimes implemented as "fat pointers", typically two or three times the size of a simple function pointer, in order to deal with virtual methods and virtual inheritance [citation needed].
When an object is created, a pointer to this table, called the virtual table pointer, vpointer or VPTR, is added as a hidden member of this object. As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table.
C++ generally prohibits forward references, but they are allowed in the special case of class members. Since the member function accessor cannot be compiled until the compiler knows the type of the member variable myValue, it is the compiler's responsibility to remember the definition of accessor until it sees myValue's declaration.
A class in C++ is a user-defined type or data structure declared with any of the keywords class, struct or union (the first two are collectively referred to as non-union classes) that has data and functions (also called member variables and member functions) as its members whose access is governed by the three access specifiers private, protected or public.
All virtual functions must be class member functions, and all (non-static) class member functions are called with the __thiscall calling convention (unless the member function takes a variable number of arguments, in which case it is called with __cdecl). The __thiscall calling convention passes a pointer to the calling class instance (commonly ...
In object-oriented programming, when a derived class inherits from a base class, an object of the derived class may be referred to via a pointer or reference of the base class type instead of the derived class type. If there are base class methods overridden by the derived class, the method actually called by such a reference or pointer can be ...
/*Ruby has three member variable types: class, class instance, and instance. */ class Dog # The class variable is defined within the class body with two at-signs # and describes data about all Dogs *and* their derived Dog breeds (if any) @@sniffs = true end mutt = Dog. new mutt. class. sniffs #=> true class Poodle < Dog # The "class instance variable" is defined within the class body with a ...
a variable definition for variable time_keeper of class TimeKeeper, initialized with an anonymous instance of class Timer or; a function declaration for a function time_keeper that returns an object of type TimeKeeper and has a single (unnamed) parameter, whose type is a (pointer to a) function [Note 1] taking no input and returning Timer objects.