Does the standard ever mention the phrase "function prototype"? Many
C++ books make a big fuss about "function prototypes". They use it in
the sense "function declaration that is not a definition". All names
must be declared before use, and some uses of some types of names need
a definition too. So what's so special about funcions? I know one
could call undeclared functions in C, and so functions were different,
but in C++ all names must be declared before use, so why fuss over
functions?

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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-L. Peter Deutsch
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Prateek R Karandikar wrote:
> Does the standard ever mention the phrase "function prototype"? Many
> C++ books make a big fuss about "function prototypes". They use it in
> the sense "function declaration that is not a definition".

Strictly speaking, the term "function prototype" is C terminology, not
C++. It's defined in the C standard 6.2.1/2: "A function prototype is a
declaration of a function that declares the types of its parameters"

Such terminology makes sense in C as declarations like

   int foo();      // a declaration, *not* a prototype

and

   int foo(void);  // a declaration that's a prototype

have very different meaning. In C++ there is no such difference, so we
can say that every function declaration is a prototype. Notice that this
also includes declarations that *are* definitions. The very common use
of the term "prototype" to identify "declarations that are not
definition" is thus not completely correct. (But I'm pretty sure I must
have used this incorrect terminology several times myself... ;)

BTW, a full-text search in the C++ reveals that the word "prototype" is
used exactly 10 times (you did try to do a search before asking, right? ;)

Apart from three occurrences in the index and three references to C
prototypes, the word is used in 3.3.3 to define the concept of
"function-prototype-scope". Such concept is indeed related only to
declarations that are not definitions, but only because function
definitions trigger the broader concept of local-scope described in 3.3.2.

There is finally a reference to "function prototype" in 17.3.1.3/1, but
as the term has never been defined, it's probably a misprint.

> All names
> must be declared before use, and some uses of some types of names need
> a definition too. So what's so special about funcions? I know one
> could call undeclared functions in C, and so functions were different,
> but in C++ all names must be declared before use, so why fuss over
> functions?

Remember that in C++ functions may be overloaded. The presence and/or
absence of an overloaded function declaration (==prototype!) before the
actual use of the function's name does matter.

Alberto

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