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Function pointers allow different code to be executed at runtime. They can also be passed to a function to enable callbacks. Function pointers are supported by third-generation programming languages (such as PL/I, COBOL, Fortran, [1] dBASE dBL [clarification needed], and C) and object-oriented programming languages (such as C++, C#, and D). [2]
Each pointer has a type it points to, but one can freely cast between pointer types (but not between a function pointer and an object pointer). A special pointer type called the “void pointer” allows pointing to any (non-function) object, but is limited by the fact that it cannot be dereferenced directly (it shall be cast).
With a GNU Compiler Collection (GCC) extension, a nested function [15] can be used and a function pointer can emulate closures, provided the function does not exit the containing scope. The next example is invalid because adder is a top-level definition (depending on compiler version, it could produce a correct result if compiled with no ...
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 ...
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
A built-in function, or builtin function, or intrinsic function, is a function for which the compiler generates code at compile time or provides in a way other than for other functions. [23] A built-in function does not need to be defined like other functions since it is built in to the programming language. [24]
The concept of the virtual function solves the following problem: 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.
This avoids having to use "fat" function pointers for nested functions which carry both the code address and the static link. [8] [9] [10] This, however, conflicts with the desire to make the stack non-executable for security reasons. In the esoteric programming language Befunge, a trampoline is an instruction to skip the next cell in the ...