[Courses] Absolute Beginning C: void?

[Kelly Martin]

On Mon, Feb 6, 2012 at 12:12 AM, jim <jim at well.com> wrote:

>
>
>    As to void for arguments, prototyping is basically
> declaring a function, in my (limited) experience as a
> matter of smoothing the way for functions other than
> main that are in a particular file.
>
> void myfunc();
>    /* declares myfunc to be a function that takes no
>       arguments and does not return anything.
>    */ // comment delimiter style pointers, anyone?
>
> // I'm surmising that
> void myfunk(void);
>    /* declares myfunk identically as the declaration
>       (prototype) of myfunc above. */
>
> // It's silly code, but what about
> void myfunny(void, void, void)
>    /* takes three nothings-at-all passed in. If I
>       were the compiler I'd at least kick out a
>       warning about smart-asses.
>    */
>
>
The first declares myfunc as a function that returns nothing and takes
unspecified arguments.  Such a declaration is deprecated under C99.

The second declares myfunc as a function that returns nothing and takes no
arguments.

The third is a syntax error: "test.c:1: error: 'void' must be the only
parameter" is gcc's complaint to that prototype.

Note that the first and the second are *not* equivalent.  The first gives
the compiler no information about the arguments, while the second
explicitly says that the function takes no arguments.  The reason behind
this is (of course) historical.

Kelly