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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.
The C99 Language Specification ( ISO9899:1999 ) has the following warning in section 6.3.2.3 Pointers : "A pointer to an object or incomplete type may be converted to a pointer to a different object or incomplete type. If the resulting pointer is not correctly aligned for the pointed-to type, the behavior is undefined."
Something similar to "fat pointers" specifically for Intel's real-mode segment:offset addressing on x86 processors, containing both a deliberately denormalized pointer to a shared code entry point and some info to still distinguish the different callers in the shared code. While, in an open system, pointer-normalizing 3rd-party instances (in ...
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. This avoids having to use "fat" function pointers for nested functions which carry both the code address and the static link.
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.
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.
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 ...
The d-pointer pattern is one of the implementations of the opaque pointer. It is commonly used in C++ classes due to its advantages (noted below). A d-pointer is a private data member of the class that points to an instance of a structure. This method allows class declarations to omit private data members, except for the d-pointer itself. [6]