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Groups > comp.lang.c > #120516

Re: Set the result of void function

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Set the result of void function
Date 2017-09-28 18:45 -0700
Organization None to speak of
Message-ID <lnefqquvko.fsf@kst-u.example.com> (permalink)
References (16 earlier) <oqj43k$g9l$1@dont-email.me> <uB9zB.1550017$WI6.973316@fx30.am4> <oqjk7g$h3p$1@dont-email.me> <ln7ewiwon8.fsf@kst-u.example.com> <5b6b3759-5c3e-4b65-9c54-a96ccc0dd393@googlegroups.com>

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David Kleinecke <dkleinecke@gmail.com> writes:
> On Thursday, September 28, 2017 at 1:32:04 PM UTC-7, Keith Thompson wrote:
>> It is 100% clear that the program of which the above main function is a
>> part has undefined behavior.  If a function is declared with (), then
>> it's the caller's responsibility to call it with the correct number and
>> type(s) of arguments.  If the call is inconsistent with the definition
>> (which in this case is probably in some other source file), then the
>> behavior is undefined.
>> 
>> There is no possible definition of the fn function that could be
>> consistent with all 4 calls shown above.  In fact, any definition could
>> be consistent with at most one of them.
>> 
>> Problem: Non-prototyped functions are error-prone.  Solution: Don't use
>> them.
>
> As nearly as I can tell it would be possible to use
> non-prototyped functions where we now use variadic
> functions. I think that is a bad idea. But ...

The behavior would be undefined.

Given:

    printf("%d\n", 42);
    printf("%s\n", "hello");

there is no way to declare and define printf such that both calls will
have defined behavior other than by using the ", ..." syntax.

Any call to a variadic function has undefined behavior unless a correct
prototype for that function is visible.

-- 
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"

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Thread

Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-19 14:23 -0700
  Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-19 14:38 -0700
    Re: Set the result of void function gordonb.tfand@burditt.org (Gordon Burditt) - 2017-09-19 17:16 -0500
    Re: Set the result of void function "Pascal J. Bourguignon" <pjb@informatimago.com> - 2017-09-20 00:39 +0200
      Re: Set the result of void function James Kuyper <jameskuyper@verizon.net> - 2017-09-19 22:06 -0400
        Re: Set the result of void function "Pascal J. Bourguignon" <pjb@informatimago.com> - 2017-09-20 06:51 +0200
          Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-20 10:55 +0100
            Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-20 12:11 +0100
            Re: Set the result of void function fir <profesor.fir@gmail.com> - 2017-09-20 07:17 -0700
          Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-20 11:28 +0100
          Re: Set the result of void function mark.bluemel@gmail.com - 2017-09-20 03:30 -0700
            Re: Set the result of void function fir <profesor.fir@gmail.com> - 2017-09-20 06:53 -0700
              Re: Set the result of void function Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-09-21 03:50 -0500
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-21 11:00 +0100
                Re: Set the result of void function scott@slp53.sl.home (Scott Lurndal) - 2017-09-21 12:39 +0000
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-21 14:12 +0100
                Re: Set the result of void function scott@slp53.sl.home (Scott Lurndal) - 2017-09-21 13:51 +0000
                Re: Set the result of void function Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-09-21 08:36 -0600
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-21 17:51 +0100
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-21 10:06 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-22 08:51 +0200
                Plunging innocent people into poverty (Was: Set the result of void function) gazelle@shell.xmission.com (Kenny McCormack) - 2017-09-23 09:31 +0000
                Re: Plunging innocent people into poverty (Was: Set the result of void function) David Brown <david.brown@hesbynett.no> - 2017-09-23 12:09 +0200
                Re: Plunging innocent people into poverty (Was: Set the result of void function) gazelle@shell.xmission.com (Kenny McCormack) - 2017-09-23 10:25 +0000
                Re: Plunging innocent people into poverty Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-09-23 10:43 -0600
                Re: Plunging innocent people into poverty supercat@casperkitty.com - 2017-09-23 10:41 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-22 09:37 +0200
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-22 11:27 +0100
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-22 14:42 +0200
                Re: Set the result of void function Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-09-24 12:09 +0000
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 08:31 +0200
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 03:52 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 13:25 +0200
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 04:58 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 14:20 +0200
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-25 13:44 +0100
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 15:09 +0200
                Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-25 05:44 -0700
                Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-25 05:58 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 15:15 +0200
                Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-25 06:46 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-25 16:01 +0200
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 07:18 -0700
                Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-25 07:55 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-25 08:49 -0700
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 09:21 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-25 09:51 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-25 21:57 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-25 15:03 -0700
                Re: Set the result of void function Öö Tiib <ootiib@hot.ee> - 2017-09-25 21:34 -0700
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-26 04:28 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-27 08:26 +0200
                Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-27 11:48 -0400
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 08:54 +0200
                Re: Set the result of void function gordonb.iddsu@burditt.org (Gordon Burditt) - 2017-09-28 23:33 -0500
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-27 09:15 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-27 17:50 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-27 10:35 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-27 18:47 +0100
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-27 10:52 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-27 11:10 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 09:10 +0200
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-27 11:06 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-27 20:01 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-27 12:26 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-27 20:38 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-27 13:00 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-27 21:54 +0100
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-27 14:12 -0700
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-27 14:34 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-27 23:16 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-27 16:09 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 01:12 +0100
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-28 02:03 +0100
                Re: Set the result of void function Ian Collins <ian-news@hotmail.com> - 2017-09-28 17:31 +1300
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 09:55 +0200
                Re: Set the result of void function Ian Collins <ian-news@hotmail.com> - 2017-09-28 21:00 +1300
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 10:48 +0100
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 13:20 +0200
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-28 11:29 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-27 20:27 -0700
                Re: Set the result of void function Gareth Owen <gwowen@gmail.com> - 2017-09-29 19:30 +0100
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-29 19:45 +0100
                Re: Set the result of void function Jerry Stuckle <jstucklex@attglobal.net> - 2017-09-29 14:49 -0400
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-27 15:07 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 09:42 +0200
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 13:55 +0100
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 17:22 +0200
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 09:14 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 20:13 +0200
                Re: Set the result of void function Gareth Owen <gwowen@gmail.com> - 2017-09-29 19:42 +0100
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-28 09:14 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 09:25 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 20:17 +0200
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 17:39 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-28 10:10 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 19:05 +0100
                Re: Set the result of void function "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-09-28 14:20 -0400
                Re: Set the result of void function Ian Collins <ian-news@hotmail.com> - 2017-09-29 07:52 +1300
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-28 11:59 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-28 18:50 +0100
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 19:47 +0100
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 21:57 +0200
                Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-28 16:14 -0400
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-28 13:17 -0700
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 21:23 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 13:55 -0700
                Re: Set the result of void function Gareth Owen <gwowen@gmail.com> - 2017-09-29 19:50 +0100
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-28 13:57 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-28 23:18 +0200
                Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-28 17:38 -0400
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-28 15:54 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-29 08:59 +0200
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 14:43 -0700
                Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-29 10:43 +0200
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-29 07:43 -0700
                Re: Set the result of void function Gareth Owen <gwowen@gmail.com> - 2017-09-30 19:21 +0100
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-30 19:45 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 13:31 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-28 13:41 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 14:07 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-28 16:25 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 18:45 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-28 19:54 -0700
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-28 20:51 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-28 22:39 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-29 09:16 -0700
                Re: Set the result of void function gazelle@shell.xmission.com (Kenny McCormack) - 2017-09-29 16:17 +0000
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 11:05 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-29 11:23 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-29 12:15 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 16:04 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-29 16:44 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-30 10:04 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-30 10:33 -0700
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-29 11:26 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 16:03 -0700
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-29 09:44 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 11:15 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-29 11:35 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 16:11 -0700
                Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-29 16:14 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-30 08:55 -0700
                Re: Set the result of void function jameskuyper@verizon.net - 2017-09-29 11:36 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-29 12:05 +0100
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-29 12:17 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-29 09:15 -0700
                Re: Set the result of void function Ian Collins <ian-news@hotmail.com> - 2017-09-29 09:42 +1300
                Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-28 21:55 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 14:12 -0700
                Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-28 17:22 -0400
                Re: Set the result of void function Gareth Owen <gwowen@gmail.com> - 2017-09-29 19:50 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 09:00 -0700
                Re: Set the result of void function supercat@casperkitty.com - 2017-09-28 09:35 -0700
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-28 10:57 -0700
                Re: Set the result of void function Thiago Adams <thiago.adams@gmail.com> - 2017-09-25 10:35 -0700
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 06:57 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-25 16:32 +0100
                Re: Set the result of void function Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-09-25 08:43 -0700
                Re: Set the result of void function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-09-25 22:12 +0100
                Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-25 09:03 -0700
                Re: Set the result of void function Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-09-25 14:17 +0000
          Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-20 11:32 -0400
        Re: Set the result of void function fir <profesor.fir@gmail.com> - 2017-09-20 01:50 -0700
          Re: Set the result of void function David Kleinecke <dkleinecke@gmail.com> - 2017-09-20 15:56 -0700
  Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-19 23:01 +0100
    Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-20 15:40 +0200
      Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-20 08:50 -0700
        Re: Set the result of void function David Brown <david.brown@hesbynett.no> - 2017-09-20 22:52 +0200
          Re: Set the result of void function supercat@casperkitty.com - 2017-09-20 15:04 -0700
    Re: Set the result of void function supercat@casperkitty.com - 2017-09-20 07:39 -0700
  Re: Set the result of void function jameskuyper@verizon.net - 2017-09-19 15:18 -0700
    Re: Set the result of void function bartc <bc@freeuk.com> - 2017-09-20 01:21 +0100
      Re: Set the result of void function jameskuyper@verizon.net - 2017-09-19 19:40 -0700
  Re: Set the result of void function rockbrentwood@gmail.com - 2017-09-19 16:36 -0700
    Re: Set the result of void function James Kuyper <jameskuyper@verizon.net> - 2017-09-19 22:13 -0400
    Re: Set the result of void function gazelle@shell.xmission.com (Kenny McCormack) - 2017-09-22 01:48 +0000
  Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-19 19:36 -0700
  Re: Set the result of void function mark.bluemel@gmail.com - 2017-09-20 01:00 -0700
    Re: Set the result of void function fir <profesor.fir@gmail.com> - 2017-09-20 02:01 -0700
  Re: Set the result of void function Keith Thompson <kst-u@mib.org> - 2017-09-20 08:36 -0700
  Re: Set the result of void function "James R. Kuyper" <jameskuyper@verizon.net> - 2017-09-20 11:36 -0400
  Re: Set the result of void function John Bode <jfbode1029@gmail.com> - 2017-09-20 15:30 -0700

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