Re: Write a C program that does NOT use time!

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: Write a C program that does NOT use time!
Date	2016-11-17 09:07 -0800
Organization	None to speak of
Message-ID	<lnfumqghly.fsf@kst-u.example.com> (permalink)
References	<o0eqoq$t9u$1@dont-email.me> <o0f3e7$qfp$2@dont-email.me> <o0kllu$n53$1@dont-email.me>

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Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
> On Tuesday November 15 2016 08:44, in comp.lang.c, "Mr. Man-wai Chang"
> <toylet.toylet@gmail.com> wrote:
[...]
>> void main() {
>
> 3) int main(void) {
>
>>    exit(0);
>
> 4) if main() function is defined as void main(), then
>      exit(0);
>    is (IMHO) superfluous
[...]

For hosted implementations, there is of course no good reason to use
void main() or void main(void).  But implementations are permitted
to permit it.

If the main function is properly defined as `int main(void)`, then
`exit(0)` is superfluous; reaching the closing `}` does an implicit
`return 0;`.  This rule was added in C99, so either `exit(0);` or
`return 0;` might be needed if your code might be compiled with
a pre-C99 or otherwise non-conforming compiler (or if the exit or
return appears other than at the very end of main()).

"If the return type is not compatible with int, the termination
status returned to the host environment is unspecified." (N1570
5.1.2.2.3), so if you use `void main()` *and* the implementation
permits it, `exit(0)` might be required (and `return 0;` would
be invalid).

Another very real possibility is that an implementation could permit
(fail to diagnose) `void main(void)`, but not document its behavior.
In that case, the behavior is undefined.

For freestanding implementations, the name and type of the entry point
are implementation-defined.  If the implementation says you have to use
`void mane(void)`, that's what you have to use.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-15 19:16 +0800
  Re: Write a C program that does NOT use time! Robert Spanjaard <spamtrap@arumes.com> - 2016-11-15 13:30 +0100
    Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-15 21:11 +0800
      Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-16 01:42 +0800
  Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-15 21:44 +0800
    Re: Write a C program that does NOT use time! jameskuyper@verizon.net - 2016-11-16 06:52 -0800
    Re: Write a C program that does NOT use time! Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-11-17 11:26 -0500
      Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-18 01:00 +0800
      Re: Write a C program that does NOT use time! Keith Thompson <kst-u@mib.org> - 2016-11-17 09:07 -0800
  Re: Write a C program that does NOT use time! "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-15 09:46 -0800
    Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-16 11:46 +0800
      Re: Write a C program that does NOT use time! Mark Storkamp <mstorkamp@yahoo.com> - 2016-11-16 08:09 -0600
        Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-16 22:15 +0800
          Re: Write a C program that does NOT use time! Mark Storkamp <mstorkamp@yahoo.com> - 2016-11-16 09:05 -0600
            Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-17 22:13 +0800
        Re: Write a C program that does NOT use time! "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-17 06:21 -0800
          Re: Write a C program that does NOT use time! Mark Storkamp <mstorkamp@yahoo.com> - 2016-11-17 09:36 -0600
            Re: Write a C program that does NOT use time! "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-17 07:45 -0800
          Re: Write a C program that does NOT use time! Jerry Stuckle <jstucklex@attglobal.net> - 2016-11-17 11:47 -0500
            Re: Write a C program that does NOT use time! "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-18 00:57 +0800
              Re: Write a C program that does NOT use time! Robert Wessel <robertwessel2@yahoo.com> - 2016-11-17 20:11 -0600
                Re: C on IBM mainframes "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-18 17:30 +0800
                Re: C on IBM mainframes Robert Wessel <robertwessel2@yahoo.com> - 2016-11-21 03:19 -0600
                Re: C on IBM mainframes "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-21 19:12 +0800
                Re: C on IBM mainframes "J. Clarke" <j.clarke.873638@gmail.com> - 2016-12-04 07:40 -0500
                Re: C on IBM mainframes "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-12-04 20:57 +0800
          Re: Write a C program that does NOT use time! David Brown <david.brown@hesbynett.no> - 2016-11-18 10:32 +0100

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