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Groups > comp.lang.c > #106184

Re: va_start without the first argument?

Newsgroups comp.lang.c
Date 2017-03-15 15:16 -0700
References (11 earlier) <lnh92vkf22.fsf@kst-u.example.com> <UcVxA.62280$Bp6.51791@fx36.iad> <ln4lyvk8ql.fsf@kst-u.example.com> <931c4a06-8f14-4c60-8a41-f34b36d07563@googlegroups.com> <slrn3vfsocje8a.ffd.ike@iceland.freeshell.org>
Message-ID <1486f63d-baaf-4656-b264-0ff123eedeae@googlegroups.com> (permalink)
Subject Re: va_start without the first argument?
From supercat@casperkitty.com

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On Wednesday, March 15, 2017 at 4:59:04 PM UTC-5, Ike Naar wrote:
> On 2017-03-14, supercat wrote:
> > The above will fail compilation, but changing the mac2 definition to
> >
> >     #define mac2(x) mac1(x)
> >
> > will fix it.
> 
> What's the difference between
> 
>     #define mac2(x) mac1(x)
> 
> and
> 
>     #define mac2(x) mac1(x)
> 
> ?

For the latter, I meant

    #define mac2(x) mac1((x))

For situations where mac1 is supposed to behave like a function that accepts
a single value, the corner cases where the macro would fail are pretty rare,
but the extra parentheses will take care of them, albeit at the cost of
masking some problems that probably should be errors (e.g. if mac2 is passed
a macro that expands to two comma-separated items, the parentheses would turn
the comma from a separator into an operator, but I know of no other way to
add punctuation around a macro argument that will prevent an expression that
contains a comma which is enclosed in {} or [] but not () from being treated
as two arguments.

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Thread

va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 11:57 -0800
  Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 12:04 -0800
  Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-10 12:32 -0800
    Re: va_start without the first argument? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-03-10 15:51 -0500
    Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 14:36 -0800
      Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 14:53 -0800
        Re: va_start without the first argument? Robert Wessel <robertwessel2@yahoo.com> - 2017-03-10 17:14 -0600
          Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 15:37 -0800
            Re: va_start without the first argument? Robert Wessel <robertwessel2@yahoo.com> - 2017-03-10 23:12 -0600
              Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 10:29 -0700
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 11:31 -0700
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-13 18:40 +0000
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 12:31 -0700
            Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-11 19:53 +0100
              Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-11 19:05 +0000
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-11 11:56 -0800
              Re: va_start without the first argument? antispam@math.uni.wroc.pl - 2017-03-12 05:41 +0000
              Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-12 13:52 +0100
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-12 14:40 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-12 18:13 +0100
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-12 18:04 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-12 21:04 +0100
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-12 21:02 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-12 22:40 +0100
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-12 15:51 -0700
                Re: va_start without the first argument? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-03-12 16:52 -0700
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-13 00:56 +0100
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-13 09:17 -0700
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-13 17:54 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-13 22:12 +0100
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-13 22:48 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 13:46 +0100
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-14 13:37 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 15:24 +0100
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-14 08:25 -0700
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 17:02 +0100
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-14 09:45 -0700
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-14 09:15 -0700
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-14 10:02 -0700
                Re: va_start without the first argument? jt@toerring.de (Jens Thoms Toerring) - 2017-03-14 20:32 +0000
                Re: va_start without the first argument? raltbos@xs4all.nl (Richard Bos) - 2017-03-14 07:44 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 13:38 +0100
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-14 08:57 -0700
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-13 11:21 -0700
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-13 18:33 +0000
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-13 22:08 +0100
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-13 15:23 -0700
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 13:58 +0100
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-14 09:18 -0700
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 16:52 +0000
                Re: va_start without the first argument? Keith Thompson <kst-u@mib.org> - 2017-03-14 11:34 -0700
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 18:54 +0000
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-14 13:30 -0700
                Re: va_start without the first argument? Ike Naar <ike@iceland.freeshell.org> - 2017-03-15 21:55 +0000
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-15 15:16 -0700
                Re: va_start without the first argument? Philip Lantz <prl@canterey.us> - 2017-03-23 21:04 -0700
                Re: va_start without the first argument? David Brown <david.brown@hesbynett.no> - 2017-03-14 21:48 +0100
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 14:01 +0000
                Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-14 07:42 -0700
                Re: va_start without the first argument? scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 12:38 +0000
                Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-13 01:11 +0100
                Re: va_start without the first argument? Ian Collins <ian-news@hotmail.com> - 2017-03-13 15:43 +1300
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-13 10:36 +0000
                Re: va_start without the first argument? Ian Collins <ian-news@hotmail.com> - 2017-03-14 07:33 +1300
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-13 19:00 +0000
                Re: va_start without the first argument? Ian Collins <ian-news@hotmail.com> - 2017-03-14 08:05 +1300
                Re: va_start without the first argument? BartC <bc@freeuk.com> - 2017-03-13 23:10 +0000
                Re: va_start without the first argument? Ian Collins <ian-news@hotmail.com> - 2017-03-14 17:38 +1300
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-14 05:48 -0700
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 12:12 -0700
                Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-12 19:39 +0100
  Re: va_start without the first argument? jt@toerring.de (Jens Thoms Toerring) - 2017-03-10 20:49 +0000
    Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-10 14:41 -0800
      Re: va_start without the first argument? John Bode <jfbode1029@gmail.com> - 2017-03-10 16:05 -0800
        Re: va_start without the first argument? jacob navia <jacob@jacob.remcomp.fr> - 2017-03-11 21:47 +0100
          Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-11 13:07 -0800
            Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-11 22:24 +0100
              Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 05:44 -0700
                Re: va_start without the first argument? Jerry Stuckle <jstucklex@attglobal.net> - 2017-03-13 08:59 -0400
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 06:17 -0700
                Re: va_start without the first argument? Jerry Stuckle <jstucklex@attglobal.net> - 2017-03-13 13:27 -0400
                Re: va_start without the first argument? Jerry Stuckle <jstucklex@attglobal.net> - 2017-03-13 13:30 -0400
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 11:00 -0700
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 10:34 -0700
          Re: va_start without the first argument? antispam@math.uni.wroc.pl - 2017-03-12 06:00 +0000
          Re: va_start without the first argument? gordonb.gas5o@burditt.org (Gordon Burditt) - 2017-03-17 09:46 -0500
            Re: va_start without the first argument? supercat@casperkitty.com - 2017-03-17 09:07 -0700
        Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 05:39 -0700
          Re: va_start without the first argument? John Bode <jfbode1029@gmail.com> - 2017-03-13 11:40 -0700
            Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 12:01 -0700
              Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-13 23:17 +0100
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 16:15 -0700
                Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-14 00:26 +0100
                Re: va_start without the first argument? kikiins@gmail.com - 2017-03-13 16:51 -0700
                Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-14 01:12 +0100
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 18:24 -0700
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-13 18:57 -0700
                Re: va_start without the first argument? raltbos@xs4all.nl (Richard Bos) - 2017-03-14 07:59 +0000
                Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-14 06:45 -0700
                Re: va_start without the first argument? Robert Wessel <robertwessel2@yahoo.com> - 2017-03-13 18:20 -0500
                Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-14 00:31 +0100
    Re: va_start without the first argument? raltbos@xs4all.nl (Richard Bos) - 2017-03-13 16:51 +0000
  Re: va_start without the first argument? jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-11 19:29 +0100
  Re: va_start without the first argument? Siri Cruise <chine.bleu@yahoo.com> - 2017-03-11 12:12 -0800
  Re: va_start without the first argument? luser droog <luser.droog@gmail.com> - 2017-03-13 05:37 -0700
    Re: va_start without the first argument? luser droog <luser.droog@gmail.com> - 2017-03-15 11:45 -0700
      Re: va_start without the first argument? Thiago Adams <thiago.adams@gmail.com> - 2017-03-15 13:39 -0700

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