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Groups > comp.lang.c > #162203

Re: Padding between char array/VLA in struct?

From Ian Pilcher <arequipeno@gmail.com>
Newsgroups comp.lang.c
Subject Re: Padding between char array/VLA in struct?
Date 2021-08-02 13:59 -0500
Organization A noiseless patient Spider
Message-ID <se9fa1$ikv$1@dont-email.me> (permalink)
References <se9b5g$l2n$1@dont-email.me>

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On 8/2/21 12:48 PM, Ian Pilcher wrote:
> Given the following:
> 
>    struct foo {
>        /* other members */
>        char prefix[PREFIX_SIZE];
>        char name[];
>    };

As has been pointed out, the 'name' member is a flexible array member,
not a variable length array.  I apologize for the mistake.

Also, PREFIX_SIZE is intended to represent a macro that expands to a
positive(!) integer constant expression.

The consensus seems to be that no one can think of a good reason that a
compiler would insert padding between the 'prefix' and 'name' members,
but there's nothing in any of the language standards that would forbid
it from doing so.  That would certainly explain my failure to find any
such rule.

(_Static_assert here I come!)

Thanks!

-- 
========================================================================
Ian Pilcher                                         arequipeno@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================

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Thread

Padding between char array/VLA in struct? Ian Pilcher <arequipeno@gmail.com> - 2021-08-02 12:48 -0500
  Re: Padding between char array/VLA in struct? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-08-02 14:07 -0400
    Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 11:25 -0700
      Re: Padding between char array/VLA in struct? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-08-02 19:21 -0400
  Re: Padding between char array/VLA in struct? Bart <bc@freeuk.com> - 2021-08-02 19:11 +0100
    Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 11:27 -0700
      Re: Padding between char array/VLA in struct? Bart <bc@freeuk.com> - 2021-08-02 20:43 +0100
        Re: Padding between char array/VLA in struct? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-08-02 13:11 -0700
          Re: Padding between char array/VLA in struct? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-08-02 13:18 -0700
          Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 13:31 -0700
            Re: Padding between char array/VLA in struct? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-08-02 19:50 -0700
              Re: Padding between char array/VLA in struct? David Brown <david.brown@hesbynett.no> - 2021-08-04 14:01 +0200
        Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 13:19 -0700
        Re: Padding between char array/VLA in struct? BGB <cr88192@gmail.com> - 2021-08-03 10:40 -0500
          Re: Padding between char array/VLA in struct? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-08-03 09:10 -0700
            Re: Padding between char array/VLA in struct? BGB <cr88192@gmail.com> - 2021-08-03 12:52 -0500
              Re: Padding between char array/VLA in struct? BGB <cr88192@gmail.com> - 2021-08-04 12:05 -0500
  Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 11:12 -0700
    Re: Padding between char array/VLA in struct? Bart <bc@freeuk.com> - 2021-08-02 19:23 +0100
      Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 13:15 -0700
  Re: Padding between char array/VLA in struct? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-08-02 11:32 -0700
  Re: Padding between char array/VLA in struct? Ian Pilcher <arequipeno@gmail.com> - 2021-08-02 13:59 -0500
    Re: Padding between char array/VLA in struct? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-08-02 12:47 -0700
      Re: Padding between char array/VLA in struct? Ian Pilcher <arequipeno@gmail.com> - 2021-08-02 15:27 -0500
        Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 13:36 -0700
        Re: Padding between char array/VLA in struct? antispam@math.uni.wroc.pl - 2021-08-02 21:52 +0000
    Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-02 13:22 -0700
      Re: Padding between char array/VLA in struct? Manfred <noname@add.invalid> - 2021-08-04 17:01 +0200
        Re: Padding between char array/VLA in struct? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-04 10:11 -0700

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