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Re: pedantic gcc and const 2D arrays

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On Wed, 8 Apr 2026 20:34:43 -0700
Andrey Tarasevich <noone@noone.net> wrote:

> On Wed 4/8/2026 3:21 PM, Michael S wrote:
> > 
> > What does it mean ?
> >   
> 
> I already mentioned this issue here not so long ago.
> 
> Again, an old puzzle about C const-correctness rules goes as follows:
> 
>    Is the following initialization
> 
>      T t;
>      const T *pt = &t;
> 
>    valid for all complete object types `T`?
> 
> And the answer is "no". The above initialization is not valid if `T`
> is an array type. E.g. given
> 
>    typedef int T[10];
> 
> the above initialization contains a constraint violation. Your
> original example with 2D array is actually exactly the same thing,
> once you take into account function argument type adjustment.
> 
> This strange behavior is prescribed by
> 
>    6.7.3 Type qualifiers
>    9 If the specification of an array type includes any type
> qualifiers, the element type is so qualified, not the array type.
> 
> (quoted from C11)
> 
> So, the fact that the `const` qualifier applied to array type "falls 
> through" to individual array elements is what prevents this 
> initialization from working. There's simply no provision in other
> rules of the language (re: assignment constraints) that would permit 
> initialization of "pointer to an array of non-const elements" with a 
> "pointer to an array of const elements".
> 
> C23 changed the above to the following:
> 
>    6.7.4 Type qualifiers
>    6.7.4.1 General
>    10 If the specification of an array type includes any type 
> qualifiers, both the array and the element type are so-qualified.
> 
> I.e. now const-qualification applies not only to the elements, but
> also to the entire array type as well. With this change in place the
> above initialization becomes valid. It now falls under the "usual" 
> const-correctness rules. In C23 arrays are no longer special in such 
> contexts.
> 

Thank you.

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pedantic gcc and const 2D arrays Michael S <already5chosen@yahoo.com> - 2026-04-09 01:21 +0300
  Re: pedantic gcc and const 2D arrays Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-04-08 15:57 -0700
    Re: pedantic gcc and const 2D arrays Michael S <already5chosen@yahoo.com> - 2026-04-09 03:09 +0300
      Re: pedantic gcc and const 2D arrays 🇵🇱Jacek Marcin Jaworski🇵🇱 <jmj@energokod.gda.pl> - 2026-04-09 02:33 +0200
      Re: pedantic gcc and const 2D arrays Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-08 21:42 -0700
  Re: pedantic gcc and const 2D arrays Andrey Tarasevich <noone@noone.net> - 2026-04-08 20:34 -0700
    Re: pedantic gcc and const 2D arrays Michael S <already5chosen@yahoo.com> - 2026-04-09 11:09 +0300
    Re: pedantic gcc and const 2D arrays "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-04-09 02:38 -0700
      Re: pedantic gcc and const 2D arrays Michael S <already5chosen@yahoo.com> - 2026-04-09 14:06 +0300
        Re: pedantic gcc and const 2D arrays "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-04-09 13:09 -0700
          Re: pedantic gcc and const 2D arrays Andrey Tarasevich <noone@noone.net> - 2026-04-12 11:30 -0700
            Re: pedantic gcc and const 2D arrays Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-13 05:40 -0700

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