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Groups > comp.std.c > #1549

Re: Why are VLAs optional in C11?

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Keith Thompson <kst-u@mib.org> writes:
> John Nagle <nagle@animats.com> writes:
> [...]
>>     The problem is the semantics of fixed-size array parameters
>> (but not local fixed-size arrays).  For those, too, the size of the
>> array is just the size of a pointer.  VLA parameters just repeat
>> that mess from fixed-size arrays.
>
> No, the problem with fixed-size array parameters is that *there is no
> such thing*.  It's not true that "the size of the array is just the size
> of the pointer".  The size of the pointer is the size of the pointer.
>
>     void func(double arr[100]);
>
> is nothing more than syntactic sugar (or perhaps syntactic vinegar)
> for this:
>
>     void func(double *arr);
[...]

John, perhaps you're approaching this from the wrong direction.

You seem to be starting with the idea that `void func(double
arr[100])` defines `arr` as a parameter of array type (but
incidentally, C treats it as a parameter of pointer type).

Instead, I suggest starting with the idea that C does not have
parameters of pointer type (but incidentally, it permits pointer
parameters to be defined with array syntax).

That might make it easier to propose a consistent mechanism for
adding array or array-like parameters to the language.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-17 15:42 -0700
  Re: Why are VLAs optional in C11? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-18 01:19 +0200
    Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-17 16:23 -0700
      Re: Why are VLAs optional in C11? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-18 10:12 +0200
    Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-17 21:04 -0700
      Re: Why are VLAs optional in C11? pacman@kosh.dhis.org (Alan Curry) - 2012-08-18 05:34 +0000
        Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-17 23:07 -0700
          Re: Why are VLAs optional in C11? pacman@kosh.dhis.org (Alan Curry) - 2012-08-18 08:29 +0000
            Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-18 09:37 -0700
              Re: Why are VLAs optional in C11? pa@see.signature.invalid (Pierre Asselin) - 2012-08-19 02:27 +0000
            Re: Why are VLAs optional in C11? Ike Naar <ike@sverige.freeshell.org> - 2012-08-18 17:49 +0000
      Re: Why are VLAs optional in C11? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-18 08:32 +0200
      Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-18 02:50 -0700
      Re: Why are VLAs optional in C11? jacob navia <jacob@spamsink.net> - 2012-08-18 14:33 +0200
        Re: Why are VLAs optional in C11? Ike Naar <ike@sverige.freeshell.org> - 2012-08-18 13:23 +0000
        Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-18 13:48 -0700
          Re: Why are VLAs optional in C11? jacob navia <jacob@spamsink.net> - 2012-08-18 23:31 +0200
            Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-18 18:14 -0700
              Re: Why are VLAs optional in C11? jacob navia <jacob@spamsink.net> - 2012-08-19 09:38 +0200
                Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-19 03:07 -0700
                Re: Why are VLAs optional in C11? jacob navia <jacob@spamsink.net> - 2012-08-19 12:29 +0200
                Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-19 10:38 -0700
                Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-19 13:14 -0700
                Re: Why are VLAs optional in C11? Keith Thompson <kst-u@mib.org> - 2012-08-19 13:59 -0700
                Re: Why are VLAs optional in C11? Owen Shepherd <nntp@owenshepherd.net> - 2012-08-27 22:17 +0100
                Re: Why are VLAs optional in C11? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-28 00:34 +0200
                Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-27 19:36 -0700
                Re: Why are VLAs optional in C11? James Kuyper <jameskuyper@verizon.net> - 2012-08-27 22:54 -0400
                Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-27 22:39 -0700
        Re: Why are VLAs optional in C11? "pdx_scooter@yahoo.com" <pdx_scooter@yahoo.com> - 2022-10-01 13:15 -0700
          Re: Why are VLAs optional in C11? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-10-01 14:33 -0700
          Re: Why are VLAs optional in C11? Tomasz Stanislawski <stanislawski.tomasz@googlemail.com> - 2023-01-25 04:21 -0800
  Re: Why are VLAs optional in C11? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-17 20:54 -0400
  Re: Why are VLAs optional in C11? John Nagle <nagle@animats.com> - 2012-08-17 20:56 -0700

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