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Re: structs passed by copy

From Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups comp.lang.c
Subject Re: structs passed by copy
Date 2023-01-23 16:37 -0800
Organization None to speak of
Message-ID <87a628g440.fsf@nosuchdomain.example.com> (permalink)
References (6 earlier) <tqk855$386s5$2@dont-email.me> <87sfg2gszl.fsf@nosuchdomain.example.com> <tqkcal$393b1$1@dont-email.me> <87o7qqglva.fsf@nosuchdomain.example.com> <86fsc0hl4i.fsf@linuxsc.com>

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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>
> [...]
>
>> BTW, I was wrong about one thing:  Support for _Imaginary is optional
>> even for an implementation that predefines __STDC_IEC_559_COMPLEX__.
>> `#ifdef _Imaginary_I` can be used to detect whether an implementation
>> supports imaginary types.
>
> I don't see how you reach this conclusion.  My reading of N1570 says
> an implementation that defines __STDC_IEC_559_COMPLEX__ must have
> imaginary types.  Annex G is normative.  It clearly states that an
> implementation that defines __STDC_IEC_559_COMPLEX__ must conform to
> its specifications.  Section G.2 says _Imaginary is a keyword, and
> there are three imaginary types, float _Imaginary, double _Imaginary,
> and long double _Imaginary.  That statement (actually a combination of
> two statements in the annex) is a specification, and so any designated
> implementation must conform to it.

I believe you're correct, and I was wrong (the second time, not
the first).  I honestly don't know how I reached the conclusion
that defining __STDC_IEC_559_COMPLEX__ *doesn't* imply a requirement
to support imaginary types.  Most likely I read one document while
thinking it was a different one.

I apologize for the confusion.

> In section 7.3.1, paragraph 5 says that the two macros 'imaginary' and
> '_Imaginary_I' are defined if and only if the implementation supports
> imaginary types, but I don't see that it gives any license to overrule
> any other statement in the standard.  Annex G is clear that there are
> imaginary types, and the implementation must provide them.  I don't
> see any wiggle room at all.  What is the reasoning behind what you
> say above?

I now think that an implementation that defines __STDC_IEC_559_COMPLEX__
(which is optional) must support imaginary types as described in Annex G.
The N1570 draft, of the C11 standard, and of the N3054 draft of C23
are all consistent on this point.

Both gcc and clang define __STDC_IEC_559_COMPLEX__ but do not support
imaginary types (with command-line options to make them attempt to be
fully conforming).  I find it surprising that they would both be
non-conforming in such a seemingly obvious way.  The gcc 12.2.0 manual
doesn't even mention the _Imaginary keyword.

(Both complex and imaginary types are optional in C11.  And a conforming
implementation could support both without supporting Annex G.)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */

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structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 10:41 -0800
  Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-20 19:01 +0000
    Re: structs passed by copy Anton Shepelev <anton.txt@gmail.com> - 2023-01-20 23:01 +0300
      Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-20 21:28 +0000
        Re: structs passed by copy Kaz Kylheku <864-117-4973@kylheku.com> - 2023-01-21 09:14 +0000
        Re: structs passed by copy Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2023-01-21 10:58 -0700
          Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-21 18:00 +0000
          Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-21 16:14 -0800
            Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-22 16:00 -0500
              Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:07 -0800
              Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-22 13:27 -0800
                Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:51 -0800
                Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:51 -0800
                Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-22 17:11 -0500
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-22 16:01 -0800
                Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-22 21:22 -0500
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 10:46 +0100
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 12:15 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 21:47 +0100
                Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-23 13:21 -0800
                Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-23 23:49 +0000
                Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-24 02:46 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:18 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:45 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:54 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:26 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:38 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:53 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 06:20 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 06:56 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 07:17 -0800
                Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-24 12:56 +0000
                Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-24 07:29 -0800
                Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-23 15:44 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 16:37 -0800
                Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-23 20:13 -0500
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 17:58 -0800
                Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-24 07:53 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-24 11:14 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-24 12:02 -0800
                Re: structs passed by copy Phil Carmody <pc+usenet@asdf.org> - 2023-01-25 10:18 +0200
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-25 10:53 -0800
                Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-29 13:30 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-29 17:42 -0800
                Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-17 07:19 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 09:35 -0800
                Re: structs passed by copy John Forkosh <forkosh@panix.com> - 2023-01-30 04:24 +0000
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-29 21:10 -0800
                Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-30 13:55 -0800
                Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-17 05:57 -0800
      Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-21 05:00 -0500
        Re: structs passed by copy Anton Shepelev <anton.txt@gmail.com> - 2023-01-21 23:00 +0300
          Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-21 17:10 -0500
    Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 18:12 -0800
    Re: structs passed by copy antispam@math.uni.wroc.pl - 2023-01-21 02:28 +0000
  Re: structs passed by copy Blue-Maned_Hawk <bluemanedhawk@gmail.com> - 2023-01-20 14:09 -0500
    Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 11:26 -0800
  Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 11:22 -0800
  Re: structs passed by copy Bart <bc@freeuk.com> - 2023-01-20 20:16 +0000
    Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 19:16 -0800
      Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 21:08 -0800
      Re: structs passed by copy Bart <bc@freeuk.com> - 2023-01-21 13:30 +0000
        Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 10:27 -0800
  Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-20 21:35 -0500
  Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-20 19:01 -0800
    Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-21 17:01 -0800
  Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-21 14:59 +0100
  Re: structs passed by copy Opus <ifonly@youknew.org> - 2023-01-21 19:59 +0100
  Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-21 16:55 -0800
    Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 02:32 -0800
      Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 15:54 +0000
        Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 09:17 -0800
          Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 09:56 -0800
            Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 10:19 -0800
              Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:01 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:08 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:17 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 13:27 -0800
        Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:04 -0800
          Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 21:43 +0000
            Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 14:10 -0800
              Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 22:29 +0000
                Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 14:39 -0800
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 19:06 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 10:54 +0100
        Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 19:00 -0800
          Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-23 12:14 +0000
  Re: structs passed by copy Jorgen Grahn <grahn+nntp@snipabacken.se> - 2023-02-11 19:35 +0000
    Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-11 15:08 -0800
      Re: structs passed by copy Öö Tiib <ootiib@hot.ee> - 2023-02-11 15:56 -0800
        Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-11 16:32 -0800
          Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-02-12 01:23 -0500
            Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-12 11:24 +0100
              Re: structs passed by copy Vir Campestris <vir.campestris@invalid.invalid> - 2023-02-12 22:11 +0000
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 10:25 +0100
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 06:41 -0800
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 06:50 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 17:22 +0100
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 10:47 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 21:50 +0100
                Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-02-15 17:14 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-16 10:53 +0100
                Re: structs passed by copy scott@slp53.sl.home (Scott Lurndal) - 2023-02-16 15:22 +0000
            Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-12 11:04 -0800
          Re: structs passed by copy Öö Tiib <ootiib@hot.ee> - 2023-02-12 12:41 -0800
          Re: structs passed by copy Andrey Tarasevich <andreytarasevich@hotmail.com> - 2023-02-16 22:49 -0800
      Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-02-11 17:49 -0800
      Grammar nitpick (Was: structs passed by copy) gazelle@shell.xmission.com (Kenny McCormack) - 2023-02-12 06:30 +0000
      Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 09:32 -0800
        Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-06 09:58 -0800
          Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 11:30 -0800
            Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-06 12:59 -0800
    Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-15 01:52 -0800
      Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-16 05:20 -0800
        Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-16 16:49 +0100
        Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-26 08:12 -0800
          Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-28 05:38 -0800
            Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-28 14:18 -0800
              Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-01 05:02 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-01 10:23 -0800
                Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-01 10:42 -0800
                Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-03-01 15:13 -0800
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 04:17 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-03-05 04:17 -0800
                Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-03-05 04:55 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-03-02 10:48 +0100
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 04:07 -0800
                Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-03-02 15:08 +0100
                Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 09:22 -0800
              Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-03-01 13:34 +0000
                Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-03-01 21:42 -0500
            Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 09:36 -0800
  Re: structs passed by copy Maciej Zelma <maciej.projectmanager@gmail.com> - 2023-02-17 14:10 -0800
    Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 15:45 -0800
      Re: structs passed by copy scott@slp53.sl.home (Scott Lurndal) - 2023-02-18 00:12 +0000
        Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-02-18 02:33 -0800
    Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-02-18 00:44 -0500
      Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 22:21 -0800
  Re: structs passed by copy Bonita Montero <Bonita.Montero@gmail.com> - 2023-03-01 18:00 +0100
    Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-01 09:18 -0800
      Re: structs passed by copy Bonita Montero <Bonita.Montero@gmail.com> - 2023-03-05 14:05 +0100

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