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Re: Loops (was Re: do { quit; } else { })

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: Loops (was Re: do { quit; } else { })
Date 2025-05-12 00:43 -0700
Organization A noiseless patient Spider
Message-ID <86o6vyxoit.fsf@linuxsc.com> (permalink)
References (16 earlier) <vvpsji$4jht$1@dont-email.me> <vvr5mg$l85c$1@dont-email.me> <87wmam4xa5.fsf@nosuchdomain.example.com> <868qn2zl1m.fsf@linuxsc.com> <vvrs5j$t9go$1@dont-email.me>

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James Kuyper <jameskuyper@alumni.caltech.edu> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>
>>> James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>>> [...]
>>>
>>>> It's main potential usefulness is not in the definition of the
>>>> function, but in calls to the function.  If the calls occur in
>>>> a different translation unit from the definition, the compiler
>>>> does not have the needed information.
>>>
>>> It does if the visible declaration has the same information.
>>
>> Like 'restrict', parameter array length information, specified by
>> way of 'static', is ignored outside of function definitions.  As
>> was intended (with 'restrict' also).
>
> ? What "static" does when applied to an array parameter's length is to
> render the behavior undefined if the function is called with a pointer
> that points to an array that is shorter than the specified length.  Are
> you saying that it has no such effect except for inside the function
> definition?  I'm not sure what that would even mean - is the behavior
> undefined only for recursive calls to the function?

What I mean is that such uses of 'static' have no effect when
used in declarations that are not part of a definition.

>> Furthermore, and also like 'restrict', there is no general
>> way to verify at compile time that the stipulated condition
>> holds.
>
> As I already mentioned, if such verification could have been
> generally possible, it should have been a constraint violation.
> Because it is not possible in general, but only in certain cases,
> making the behavior undefined is the best that can be done.  Doing
> so encourages implementations to generate a diagnostic when those
> cases do come up.

It isn't just that checking the condition cannot be done in general.
To be reliable the parameter length information would need to be
part of the function's type.  That has implications for type
compatibility and also for the types of pointers-to-function.  And
it would mean that removing a 'static' array length specification on
a function definition would necessitate also changing the functions
declarations, plus any affected pointers-to-function.  Not worth it,
even if in theory it were doable.

>> Considering the above, it's better to observe the status quo, and
>> leave any diagnostics up to the discretion of the implementation,
>> rather than try to retrofit an incompatible change that would
>> make an infringement be a constraint violation that can't be
>> checked anyway.
>
> I was not suggesting any change to the status quo, [...]

I didn't mean to imply you had.

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Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-04 07:31 -0700
  Re: Loops (was Re: do { quit; } else { }) Michael S <already5chosen@yahoo.com> - 2025-05-04 18:08 +0300
    Re: Loops (was Re: do { quit; } else { }) Michael S <already5chosen@yahoo.com> - 2025-05-05 10:42 +0300
    Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-10 06:43 -0700
      Re: Loops (was Re: do { quit; } else { }) Muttley@dastardlyhq.com - 2025-05-10 15:56 +0000
        Re: Loops (was Re: do { quit; } else { }) scott@slp53.sl.home (Scott Lurndal) - 2025-05-10 17:48 +0000
          Re: Loops (was Re: do { quit; } else { }) Muttley@dastardlyhq.com - 2025-05-11 08:20 +0000
        Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-10 14:29 -0700
          Re: Loops (was Re: do { quit; } else { }) Muttley@dastardlyhq.com - 2025-05-11 08:21 +0000
            Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-11 12:02 +0200
              Re: Loops (was Re: do { quit; } else { }) Muttley@dastardlyhq.com - 2025-05-11 15:30 +0000
                Re: Loops (was Re: do { quit; } else { }) scott@slp53.sl.home (Scott Lurndal) - 2025-05-11 16:29 +0000
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-11 18:49 +0200
              Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-11 14:41 -0700
              Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-11 17:43 -0400
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-11 15:06 -0700
                Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-11 18:30 -0400
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-11 18:15 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-11 19:09 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 00:16 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-12 02:23 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 07:19 -0700
                Re: Loops (was Re: do { quit; } else { }) Richard Heathfield <rjh@cpax.org.uk> - 2025-05-12 15:34 +0100
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 22:42 -0700
                Re: Loops (was Re: do { quit; } else { }) Richard Heathfield <rjh@cpax.org.uk> - 2025-05-13 07:31 +0100
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-14 21:12 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-13 09:30 -0700
                Re: Loops (was Re: do { quit; } else { }) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-13 22:28 +0200
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-12 13:31 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-14 20:44 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-14 21:45 -0700
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-12 17:24 +0200
                Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-12 00:07 -0400
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 00:43 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-12 02:27 -0700
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-12 17:18 +0200
                Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-12 19:53 -0400
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 23:03 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-12 19:04 -0700
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-12 17:08 +0200
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-12 13:38 -0700
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-13 12:41 +0200
                Re: Loops (was Re: do { quit; } else { }) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-13 23:16 +0200
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-13 14:35 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-13 15:10 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-13 15:41 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-13 18:38 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-13 19:37 -0700
                Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-13 23:54 -0400
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-13 21:19 -0700
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-13 21:12 -0700
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-13 22:38 -0700
                Re: Loops (was Re: do { quit; } else { }) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-14 03:35 +0000
                Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-13 21:54 -0700
                Re: Loops (was Re: do { quit; } else { }) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-14 06:31 +0000
                Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-06-10 06:01 -0700
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-14 13:00 +0200
                Re: Loops (was Re: do { quit; } else { }) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-14 13:20 +0200
                Re: Loops (was Re: do { quit; } else { }) James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-05-14 23:20 -0400
                Re: Loops (was Re: do { quit; } else { }) David Brown <david.brown@hesbynett.no> - 2025-05-15 11:23 +0200
            Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-11 17:59 -0700
              Re: Loops (was Re: do { quit; } else { }) Muttley@DastardlyHQ.org - 2025-05-12 10:11 +0000
                Re: Loops (was Re: do { quit; } else { }) Michael S <already5chosen@yahoo.com> - 2025-05-12 17:09 +0300
      Re: Loops (was Re: do { quit; } else { }) Michael S <already5chosen@yahoo.com> - 2025-05-11 01:09 +0300
        Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-11 17:30 -0700
          Re: Loops (was Re: do { quit; } else { }) Michael S <already5chosen@yahoo.com> - 2025-05-12 16:18 +0300
            Re: Loops (was Re: do { quit; } else { }) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-05-14 11:09 -0700
          Re: Loops (was Re: do { quit; } else { }) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-05-13 15:57 +0200
  Re: Loops (was Re: do { quit; } else { }) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-04 13:52 -0700

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