Re: structs passed by copy

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: structs passed by copy
Date	2023-01-24 07:53 -0800
Organization	A noiseless patient Spider
Message-ID	<86bkmogc9c.fsf@linuxsc.com> (permalink)
References	(7 earlier) <87sfg2gszl.fsf@nosuchdomain.example.com> <tqkcal$393b1$1@dont-email.me> <87o7qqglva.fsf@nosuchdomain.example.com> <86fsc0hl4i.fsf@linuxsc.com> <87a628g440.fsf@nosuchdomain.example.com>

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> 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.

No apology needed.

>> 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.

What may have happened is that gcc implemented complex types
around the time of C99, when complex types were required but
Annex G was merely informative (and the last sentence of G.1
says "should conform" rather than "shall conform" as it does
in C11).  As far as C99 is concerned, gcc and clang are both
conforming.

Then, when C11 came along, no one noticed the switch in status of
Annex G, and since relatively few people care about imaginary
types, no one noticed that their absence violated the rules in
the new standard.  It may be the case that there are other parts
of Annex G that either gcc or clang do not satisfy, perhaps
because no one has pointed out the (possible) deficiencies.

It would be nice if some energetic person would enter a bug
report on the gcc bug list site, regarding the missing imaginary
types.  I have put in gcc bug reports in the past but don't have
as much time for that now.

Thread

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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