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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].
Function pointers allow referencing functions with a particular signature. For example, to store the address of the standard function abs in the variable my_int_f : int ( * my_int_f )( int ) = & abs ; // the & operator can be omitted, but makes clear that the "address of" abs is used here
A basic example is in the argv argument to the main function in C (and C++), which is given in the prototype as char **argv—this is because the variable argv itself is a pointer to an array of strings (an array of arrays), so *argv is a pointer to the 0th string (by convention the name of the program), and **argv is the 0th character of the ...
In C and C++, the type signature is declared by what is commonly known as a function prototype. In C/C++, a function declaration reflects its use; for example, a function pointer with the signature (int)(char, double) would be called as:
In computer programming, a callback is a function that is stored as data (a reference) and designed to be called by another function – often back to the original abstraction layer. A function that accepts a callback parameter may be designed to call back before returning to its caller which is known as synchronous or blocking.
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 February 2025. General-purpose programming language "C programming language" redirects here. For the book, see The C Programming Language. Not to be confused with C++ or C#. C Logotype used on the cover of the first edition of The C Programming Language Paradigm Multi-paradigm: imperative (procedural ...
Differences between C and C++ linkage and calling conventions can also have subtle implications for code that uses function pointers. Some compilers will produce non-working code if a function pointer declared extern "C" points to a C++ function that is not declared extern "C". [22] For example, the following code:
Examples of, and arguments for, Jump Tables via Function Pointer Arrays in C/C++; Example code generated by 'Switch/Case' branch table in C, versus IF/ELSE. Example code generated for array indexing if structure size is divisible by powers of 2 or otherwise. "Arrays of Pointers to Functions" by Nigel Jones