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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.
Instances of these class templates are C++ classes that define a function call operator, and the instances of these classes can be called as if they were functions. [1] It is possible to perform very sophisticated operations without writing a new function object, simply by combining predefined function objects and function object adaptors.
A function pointer, also called a subroutine pointer or procedure pointer, is a pointer referencing executable code, rather than data. Dereferencing the function pointer yields the referenced function , which can be invoked and passed arguments just as in a normal function call.
A function signature consists of the function prototype. It specifies the general information about a function like the name, scope and parameters. Many programming languages use name mangling in order to pass along more semantic information from the compilers to the linkers. In addition to mangling, there is an excess of information in a ...
In some languages, a pointer can reference executable code, i.e., it can point to a function, method, or procedure. A function pointer will store the address of a function to be invoked. While this facility can be used to call functions dynamically, it is often a favorite technique of virus and other malicious software writers.
The trampoline is a small piece of code which is constructed on the fly on the stack when the address of a nested function is taken. The trampoline sets up the static link pointer, which allows the nested function to access local variables of the enclosing function. The function pointer is then simply the address of the trampoline.
In such a case, a common solution is to create a clone (or similar) virtual function that creates and returns a copy of the derived class when called. A member function can also be made "pure virtual" by appending it with = 0 after the closing parenthesis and before the semicolon. A class containing a pure virtual function is called an abstract ...
Instances of such classes are called functors or function objects. Functors allow the behavior of the associated function to be parameterized (e.g. through arguments passed to the functor's constructor) and can be used to keep associated per-functor state information along with the function. Since both functors and function pointers can be ...