Re: Regarding assignment to struct

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Regarding assignment to struct
Date	2025-05-03 17:37 -0700
Organization	None to speak of
Message-ID	<87ikmhp5x3.fsf@nosuchdomain.example.com> (permalink)
References	<vv338b$16oam$1@dont-email.me> <vv4j9p$33vhj$1@dont-email.me> <vv66cu$hbtf$1@dont-email.me>

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Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> On Sat, 3 May 2025 01:14:46 -0700, Andrey Tarasevich wrote:
>> Virtually every C project relies on assignment of structures.
>> Passing-returning structs by value might be more rare (although
>> perfectly valid and often appropriate too), but assignment...
>> assignment is used by everyone everywhere without even giving it a
>> second thought.
>
> There is a caveat, to do with alignment padding: will this always have a 
> defined value?

I don't believe so.  In a quick look, I don't see anything in
the standard that explicitly addresses this, but I believe that a
conforming implementation could implement structure assignment by
copying the individual members, leaving any padding in the target
undefined.

(A quibble about your wording: I don't believe padding has a "value"
as the term is used by the standard.)

The question is whether the "value" of a struct object consists
only of the values of its members.  I'd say it does, but unless
I'm missing something the standard doesn't say so explicitly.

Finally, why would you care?e

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */

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Regarding assignment to struct Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-05-02 18:34 +0000
  Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-02 13:17 -0700
  Re: Regarding assignment to struct Barry Schwarz <schwarzb@delq.com> - 2025-05-02 13:35 -0700
    That depends... (Was: Regarding assignment to struct) gazelle@shell.xmission.com (Kenny McCormack) - 2025-05-02 20:44 +0000
      Re: That depends... (Was: Regarding assignment to struct) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-05-03 01:13 +0000
        Re: That depends... (Was: Regarding assignment to struct) Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-05-03 02:28 +0000
        Re: That depends... (Was: Regarding assignment to struct) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-03 06:17 +0200
        Re: That depends... (Was: Regarding assignment to struct) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-03 04:31 +0000
          Re: That depends... (Was: Regarding assignment to struct) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-03 05:11 +0000
            Re: That depends... (Was: Regarding assignment to struct) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-05 12:30 +0200
              Re: That depends... (Was: Regarding assignment to struct) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-05 18:47 +0000
          Re: That depends... (Was: Regarding assignment to struct) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-04 11:05 -0700
        Re: That depends... (Was: Regarding assignment to struct) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-03 00:47 -0400
        Re: That depends... (Was: Regarding assignment to struct) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-04 10:59 -0700
          Re: That depends... (Was: Regarding assignment to struct) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-05-04 18:16 +0000
  Re: Regarding assignment to struct antispam@fricas.org (Waldek Hebisch) - 2025-05-02 21:35 +0000
    Re: Regarding assignment to struct Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-05-03 01:43 +0000
  Re: Regarding assignment to struct Andrey Tarasevich <noone@noone.net> - 2025-05-03 01:14 -0700
    Re: Regarding assignment to struct Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-05-03 22:46 +0000
      Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-03 17:37 -0700
        Re: Regarding assignment to struct James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-03 23:38 -0400
          Re: Regarding assignment to struct gazelle@shell.xmission.com (Kenny McCormack) - 2025-05-04 09:25 +0000
          Re: Regarding assignment to struct scott@slp53.sl.home (Scott Lurndal) - 2025-05-04 14:27 +0000
            Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-04 18:45 +0200
          Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-04 13:20 -0700
            Re: Regarding assignment to struct scott@slp53.sl.home (Scott Lurndal) - 2025-05-05 00:41 +0000
              Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-04 18:42 -0700
              Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 21:57 -0700
            Re: Regarding assignment to struct James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-04 21:08 -0400
    Re: Regarding assignment to struct Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-05-03 22:47 +0000
    Re: Regarding assignment to struct Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-05-03 22:46 +0000
    Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-04 06:48 -0700
      Re: Regarding assignment to struct Andrey Tarasevich <noone@noone.net> - 2025-05-04 22:22 -0700
        Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-05 11:12 +0300
          Re: Regarding assignment to struct Andrey Tarasevich <noone@noone.net> - 2025-05-05 01:29 -0700
            Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-05 12:01 +0300
              Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 07:14 -0700
              Re: Regarding assignment to struct Andrey Tarasevich <noone@noone.net> - 2025-05-05 08:45 -0700
                Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-05 20:20 +0300
                Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 22:26 -0700
                Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 13:27 -0700
                Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 17:04 -0700
                Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 17:53 -0700
                Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-06 11:35 +0200
                Re: Regarding assignment to struct antispam@fricas.org (Waldek Hebisch) - 2025-05-06 17:36 +0000
                Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-06 20:46 +0200
                Re: Regarding assignment to struct scott@slp53.sl.home (Scott Lurndal) - 2025-05-06 19:22 +0000
                Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-07 09:37 +0200
                Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-06 13:06 -0700
          Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 07:03 -0700
        Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 01:26 -0700
          Re: Regarding assignment to struct Andrey Tarasevich <noone@noone.net> - 2025-05-05 10:14 -0700
            Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-08 12:45 -0700
              Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-08 22:20 +0200
        Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 01:34 -0700
          Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-05 12:03 +0300
            Re: Regarding assignment to struct gazelle@shell.xmission.com (Kenny McCormack) - 2025-05-05 11:30 +0000
            Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 13:32 -0700
              Re: Regarding assignment to struct Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-05 21:10 +0000
                Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 22:57 -0700
            Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 22:40 -0700
          Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 06:34 -0700
            Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 13:43 -0700
              Re: Regarding assignment to struct Nick Bowler <nbowler@draconx.ca> - 2025-05-06 19:06 +0000
                Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-06 13:21 -0700
                Re: Regarding assignment to struct Nick Bowler <nbowler@draconx.ca> - 2025-05-07 19:09 +0000
                Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-07 14:23 -0700
                Re: Regarding assignment to struct Nick Bowler <nbowler@draconx.ca> - 2025-05-08 12:58 +0000
                Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-07 21:17 -0700
        Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 07:56 -0700
          Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-05 20:00 +0200
        Re: Regarding assignment to struct NotAorB <atod101101@gmail.com> - 2025-05-12 16:38 -0400
  Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-03 11:46 +0200
    Re: Regarding assignment to struct Muttley@dastardlyhq.com - 2025-05-05 08:50 +0000
      Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-05 13:34 +0200
      Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-05 13:53 -0700
        Re: Regarding assignment to struct Muttley@DastardlyHQ.org - 2025-05-06 07:16 +0000
        Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-06 11:46 +0200
          Re: Regarding assignment to struct Muttley@DastardlyHQ.org - 2025-05-06 10:18 +0000
        Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-06 16:34 +0300
  Re: Regarding assignment to struct Richard Damon <richard@damon-family.org> - 2025-05-03 21:42 -0400
    Re: Regarding assignment to struct Michael S <already5chosen@yahoo.com> - 2025-05-04 11:01 +0300
      Re: Regarding assignment to struct Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-05-04 08:34 +0000
        Re: Regarding assignment to struct David Brown <david.brown@hesbynett.no> - 2025-05-04 14:06 +0200
      Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-05 21:25 -0700
      Re: Regarding assignment to struct Rosario19 <Ros@invalid.invalid> - 2025-05-12 11:23 +0200
  Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-04 07:49 -0700
  Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-04 14:09 -0700

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