Re: who invented static?

From	Tim Rentsch <txr@alumni.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: who invented static?
Date	2015-09-06 19:33 -0700
Organization	A noiseless patient Spider
Message-ID	<kfn613nnelf.fsf@x-alumni2.alumni.caltech.edu> (permalink)
References	(5 earlier) <mrv5f3$g9b$1@dont-email.me> <55E32CBB.2050001@verizon.net> <mrvcnh$fju$1@dont-email.me> <m_GEx.8461$1H1.2009@fx23.iad> <87io7wwmwu.fsf@bsb.me.uk>

Show all headers | View raw

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

> Richard Damon <Richard@Damon-Family.org> writes:
>
>> On 8/30/15 1:00 PM, David Brown wrote:
>>> On 30/08/15 18:18, James Kuyper wrote:
>>>> On 08/30/2015 10:56 AM, David Brown wrote:
>>>>> On 29/08/15 23:08, James Kuyper wrote:
>>>>>
>>>>>> The following use of "static" is new in C99, and can only occur in the
>>>>>> leading dimension of a function parameter declared as an array:
>>>>>> "If the keyword static also appears within the [ and ] of the array
>>>>>> type
>>>>>> derivation, then for each call to the function, the value of the
>>>>>> corresponding actual argument shall provide access to the first element
>>>>>> of an array with at least as many elements as specified by the size
>>>>>> expression."  6.7.6.3p7
>
> <snip>
>
>>>> Given:
>>>>
>>>>      void f(int array[static 3]);
>>>>      int large_array[6];
>>>>      int small_array[2];
>>>>      int *p = small_array;
>>>>
>>>> then f(large_array) is fine, because large_array has more than 3
>>>> elements.  However, f(small_array) violates a "shall" that occurs outside
>>>> of a constraint, because small_array has fewer than 3 elements.  The
>>>> behavior is therefore undefined.  I would have preferred that this be a
>>>> constraint violation, and I would expect any decent implementation of
>>>> C99 or later to issue the diagnostic message that would be mandatory if
>>>> it were a constraint violation - in my opinion, that possibility is the
>>>> only thing that makes this feature worthwhile.  I think that the reason
>>>> why it cannot be made a constraint violation is that f(p) is also a
>>>> violation of the same rule, and unlike f(small_array), it's not in
>>>> general easy for a compiler to identify the fact that an arbitrary
>>>> pointer points at location which violates this rule.
>
> I think it's simpler to say that it can't be a constraint because it
> can't be diagnosed.  [snip]

Not only that, but the use of 'static' could be given just
in the function definition, but not in any declarations.
The "shall" requirement still applies, but the information
simply isn't there in other translation units.

>>> But surely if g were defined:
>>>
>>>      void g(int array[3]);
>>>
>>> Then g(small_array) would still be a constraint violation?  Or is it
>>> defined behaviour to call g(small_array), and only becomes undefined if
>>> g() accesses array[2] ?
>>>
>>> It seems to me that even without the "static", g is asking for a
>>> parameter with particular characteristics, and calling g(small_array) is
>>> breaking that requirement.
>>
>> in c, this definition of g is IDENTICAL to (by a rewrite rule)
>>   void g(int *array);
>>
>> (note, the 3 is lost)
>> Thus, the passing of anything that is an int* or decays to an int*
>> (like an array of any size of int) is valid.
>>
>> Adding the static keyword changes the type of that parameter so that
>> the compiler actually remembers the needed bounds, and will check that
>> the passed array is large enough.
>
> The compiler can't always do that check but maybe you were talking about
> the example given.  Anyway, where does the idea that static changes the
> type of the parameter come from?  I don't see that at all.

Using 'static' in this way does not change the type of the
parameter.  How it behaves is analogous to type qualifiers,
eg, 'const' or 'restrict' - there is an effect on the
function definition, but no effect for calls.

Thread

who invented static? fir <profesor.fir@gmail.com> - 2015-08-29 11:40 -0700
  Re: who invented static? David Kleinecke <dkleinecke@gmail.com> - 2015-08-29 13:36 -0700
    Re: who invented static? fir <profesor.fir@gmail.com> - 2015-08-29 13:46 -0700
      Re: who invented static? David Kleinecke <dkleinecke@gmail.com> - 2015-08-29 13:53 -0700
        Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-08-29 17:08 -0400
          Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-08-30 16:56 +0200
            Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-08-30 12:18 -0400
              Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-08-30 19:00 +0200
                Re: who invented static? Richard Damon <Richard@Damon-Family.org> - 2015-08-30 13:23 -0400
                Re: who invented static? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-30 21:18 +0100
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 19:33 -0700
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 19:26 -0700
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-08-30 13:40 -0400
                Re: who invented static? supercat@casperkitty.com - 2015-08-31 06:47 -0700
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 19:20 -0700
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 18:59 -0700
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-07 10:25 +0200
                Re: who invented static? Keith Thompson <kst-u@mib.org> - 2015-09-07 01:59 -0700
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-07 12:22 +0200
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-09-07 13:04 -0400
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-07 21:25 +0200
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-09-07 15:47 -0400
                Re: who invented static? Philip Lantz <prl@canterey.us> - 2015-09-07 13:27 -0700
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-09-07 17:31 -0400
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-08 09:16 +0200
                Re: who invented static? Keith Thompson <kst-u@mib.org> - 2015-09-07 13:27 -0700
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-08 09:12 +0200
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-07 16:06 -0700
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-08 09:08 +0200
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-12 11:29 -0700
                Re: who invented static? Keith Thompson <kst-u@mib.org> - 2015-09-08 10:18 -0700
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-09-08 13:28 -0400
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-11 10:07 -0700
                Re: who invented static? Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-12 12:30 -0700
                Re: who invented static? David Brown <david.brown@hesbynett.no> - 2015-09-13 15:48 +0200
                Re: who invented static? supercat@casperkitty.com - 2015-09-29 09:04 -0700
                Re: who invented static? Keith Thompson <kst-u@mib.org> - 2015-09-29 09:18 -0700
                Re: who invented static? supercat@casperkitty.com - 2015-09-29 09:57 -0700
        Re: who invented static? fir <profesor.fir@gmail.com> - 2015-08-29 14:18 -0700
          Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-01 01:36 -0700
    Re: who invented static? Keith Thompson <kst-u@mib.org> - 2015-08-29 14:27 -0700
  Re: who invented static? Siri Cruz <chine.bleu@yahoo.com> - 2015-08-29 14:32 -0700
    Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-29 23:03 +0000
    Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-01 01:52 -0700
      Re: who invented static? Robert Wessel <robertwessel2@yahoo.com> - 2015-09-01 23:42 -0500
        Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-02 00:14 -0700
          Re: who invented static? Richard Heathfield <rjh@cpax.org.uk> - 2015-09-02 08:24 +0100
        Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-04 04:25 +0000
          Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-04 00:45 -0700
            Re: who invented static? Robert Wessel <robertwessel2@yahoo.com> - 2015-09-04 04:09 -0500
              Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-04 02:35 -0700
                Re: who invented static? Robert Wessel <robertwessel2@yahoo.com> - 2015-09-04 23:58 -0500
                Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-05 03:02 -0700
                Re: who invented static? wssimms@gmail.com - 2015-09-05 13:14 -0700
                Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-05 13:49 -0700
                Re: who invented static? Siri Cruz <chine.bleu@yahoo.com> - 2015-09-05 14:09 -0700
                Re: who invented static? gazelle@shell.xmission.com (Kenny McCormack) - 2015-09-05 22:30 +0000
                Re: who invented static? wssimms@gmail.com - 2015-09-05 20:41 -0700
                Re: who invented static? gazelle@shell.xmission.com (Kenny McCormack) - 2015-09-06 05:28 +0000
                Re: who invented static? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-09-05 22:40 -0700
                Re: who invented static? James Kuyper <jameskuyper@verizon.net> - 2015-09-06 11:42 -0400
                Re: who invented static? Robert Wessel <robertwessel2@yahoo.com> - 2015-09-05 23:38 -0500
                Re: who invented static? raltbos@xs4all.nl (Richard Bos) - 2015-09-27 21:25 +0000
                Re: who invented static? Siri Cruz <chine.bleu@yahoo.com> - 2015-09-27 14:53 -0700
                Re: who invented static? Thomas Richter <thor@math.tu-berlin.de> - 2015-09-29 01:46 +0200
                Re: who invented static? raltbos@xs4all.nl (Richard Bos) - 2015-10-02 12:52 +0000
            Re: who invented static? Siri Cruz <chine.bleu@yahoo.com> - 2015-09-04 02:34 -0700
              Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-04 02:43 -0700
              Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-05 01:30 +0000
                Re: who invented static? Siri Cruz <chine.bleu@yahoo.com> - 2015-09-04 20:52 -0700
                Re: who invented static? Robert Wessel <robertwessel2@yahoo.com> - 2015-09-05 00:03 -0500
                Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-05 09:04 +0000
                Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-05 03:02 -0700
                Re: who invented static? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-09-05 04:33 -0700
                Re: who invented static? Reinhardt Behm <rbehm@hushmail.com> - 2015-09-05 20:08 +0800
                Re: who invented static? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-09-05 05:21 -0700
                Re: who invented static? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-09-05 06:37 -0700
                Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-05 16:54 +0000
                Re: who invented static? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-09-05 11:06 +0100
                Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-05 03:17 -0700
                Re: who invented static? raltbos@xs4all.nl (Richard Bos) - 2015-09-05 19:14 +0000
                Re: who invented static? fir <profesor.fir@gmail.com> - 2015-09-05 12:59 -0700
            Re: who invented static? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-05 01:24 +0000

csiph-web