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I found in old code that when calling a void function:

void
foo() {
......
}
....
(void) foo();

I wonder why (void) is used to typecast the function.
Is there any historical reason?


Any reply from you will be appreciated.

su wrote:
> I found in old code that when calling a void function:
>
> void
> foo() {
> .....
> }
> ...
> (void) foo();
>
> I wonder why (void) is used to typecast the function.
> Is there any historical reason?
>
"cast", actors get "typecast"

The reason is usually to suppress compiler or lint warnings, but they
tend not to be a problem with functions returning void.

--
Ian Collins

Thanks. I got it.

Jack Klein wrote:
> On Thu, 22 Jan 2009 19:23:07 -0800 (PST), su <> wrote
> in comp.lang.c:
>
> > I found in old code that when calling a void function:
> >
> > void
> > foo() {
> > .....
> > }
> > ...
> > (void) foo();
> >
> > I wonder why (void) is used to typecast the function.
> > Is there any historical reason?
> >
> >
> > Any reply from you will be appreciated.
>
> There's no good reason at all to do this if foo() actually has a
> "void" return type.
>
> There are reasons for doing this is foo() actually returns a value of
> some type. Some static code checking tools and coding standards
> specify that the return value of every function should be checked or
> specifically ignored.
>
> So given:
>
> int f(int arg);
>
> ...then:
>
> f(12);
>
> ...violates the coding standard or generates a message from the code
> checking tool, whereas:
>
> (void)f(12);
>
> ...does not.
>
> The first case could be the programmer making an error and forgetting
> to check the return value.
>
> --
> Jack Klein
> Home: http://JK-Technology.Com
> FAQs for
> comp.lang.c http://c-faq.com/
> comp.lang.c++ http://www.parashift.com/c++-faq-lite/
> alt.comp.lang.learn.c-c++
> http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html

Jack Klein wrote:
> su <> wrote in comp.lang.c:
>
.... snip ...
>
>> (void) foo();
>>
>> I wonder why (void) is used to typecast the function.
>> Is there any historical reason?
>
.... snip ...
>
> int f(int arg);
>
> ...then:
>
> f(12);
>
> ...violates the coding standard or generates a message from the
> code checking tool, whereas:
>
> (void)f(12);
>
> ...does not.
>
> The first case could be the programmer making an error and
> forgetting to check the return value.

And the number of scanfs and similar calls one sees unchecked
indicate that insistance on the void usage might be helpful.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
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