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Re: function pointer question

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From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: function pointer question
Date Wed, 07 Jan 2026 18:27:02 -0800
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Andrey Tarasevich <noone@noone.net> writes:

> On Wed 1/7/2026 7:35 AM, Tim Rentsch wrote:
>
>> Andrey Tarasevich <noone@noone.net> writes:
>>
>>> On Sat 1/3/2026 12:04 PM, Chris M. Thomasson wrote:
>>>
>>>> struct object_prv_vtable {
>>>>     int (*fp_destroy) (void* const);
>>>> };
>>>
>>> And interesting piece of trivia about C function types and function
>>> type compatibility rules is that:
>>>
>>> 1.  Top-level qualifiers on function parameters are preserved as part
>>> of function type.
>>
>> Not completely wrong but not exactly right either.
>>
>>> However, such top-level qualifiers are ignored when
>>> determining function type compatibility.
>>
>> It's easier to take the point of view that top-level qualifiers
>> for function parameters don't participate in the type of the
>> function as a whole.  Taking that view is easier to understand
>> and gives results that are indistinguishable from the actual
>> rules.
>
> No, that's not entirely accurate.
>
> The C17 modifications I mentioned in my previous post stems from DR#423
>
> https://www.open-std.org/jtc1/sc22/wg14/www/docs/summary.htm#dr_423
>
> which is related to how qualifications are treated under
> _Generic`. `_Generic` operates on "exact match" basis not on "type
> compatibility" basis.  Which is why such matters suddenly become
> important.
>
> The DR itself is about qualifications on rvalues (another thing that
> "did not matter" previously), not about function parameters.  But it is
> clear that it applies to our topic as well.
>
> I have no time to research it further at the moment (will do it a bit
> later), but something tells me that `_Generic` is expected to "see"
> and distinguish the exact const-qualification of function parameters
> in function types.  If so, it might be a "useless" feature, but still..

I see you have posted a further followup.  I am responding to
that.

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function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 07:24 +0000
  Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-02 09:04 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:42 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:45 +0000
  Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 02:52 -0800
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 14:43 +0000
      Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-02 17:21 +0100
        Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 09:37 -0800
        Re: function pointer question Ben Bacarisse <ben@bsb.me.uk> - 2026-01-03 03:33 +0000
          Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-03 07:41 -0800
            Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-03 21:46 +0000
              Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-04 12:03 +0100
            Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-06 20:41 +0000
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 07:18 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 21:52 -0800
                Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-08 09:17 +0100
  Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 17:48 +0000
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:35 +0000
      Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 12:07 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-03 06:06 +0000
      Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 21:50 +0000
      Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-02 21:52 +0000
        Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-02 14:18 -0800
          Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-03 13:55 +0100
            Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-03 12:04 -0800
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-03 13:01 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 07:35 -0800
                Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 08:17 -0800
                Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-07 08:23 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 18:44 -0800
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 18:27 -0800
              Re: function pointer question Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-03 22:05 +0000
            Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-03 16:39 -0800
              Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-04 12:15 +0100
            Re: function pointer question Kaz Kylheku <046-301-5902@kylheku.com> - 2026-01-06 20:33 +0000
              Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-06 17:01 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-03 06:08 +0000
          Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-05 12:40 -0800
            Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 04:30 +0000
              Re: function pointer question "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-01-06 17:05 -0800
      Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-03 17:20 -0500
        Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-03 16:48 -0800
        Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-05 08:39 +0000
          Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 12:32 +0000
            Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-06 13:59 +0100
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 13:57 +0000
              Re: function pointer question antispam@fricas.org (Waldek Hebisch) - 2026-01-06 14:50 +0000
                Re: function pointer question highcrew <high.crew3868@fastmail.com> - 2026-01-06 21:44 +0100
                Re: function pointer question scott@slp53.sl.home (Scott Lurndal) - 2026-01-06 22:08 +0000
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-07 05:59 -0800
                Re: function pointer question antispam@fricas.org (Waldek Hebisch) - 2026-01-07 09:25 +0000
                Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-07 11:37 +0100
            Re: function pointer question Michael S <already5chosen@yahoo.com> - 2026-01-06 15:47 +0200
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 14:01 +0000
            Re: function pointer question David Brown <david.brown@hesbynett.no> - 2026-01-06 15:55 +0100
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:44 +0000
            Re: function pointer question scott@slp53.sl.home (Scott Lurndal) - 2026-01-06 15:41 +0000
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:45 +0000
            Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-06 10:58 -0500
              Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-06 16:49 +0000
                Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-06 12:09 -0500
                Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-07 21:18 +0000
              Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-09 09:14 -0800
              Re: function pointer question Andrey Tarasevich <noone@noone.net> - 2026-01-10 19:17 -0800
                Re: function pointer question "James Russell Kuyper Jr." <jameskuyper@alumni.caltech.edu> - 2026-01-10 22:39 -0500
                Re: function pointer question Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-11 11:49 -0800
        Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-05 06:47 -0500
  Re: function pointer question James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-01-02 14:03 -0500
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:41 +0000
  Re: function pointer question bart <bc@freeuk.com> - 2026-01-02 19:18 +0000
    Re: function pointer question Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-02 11:43 -0800
    Re: function pointer question Michael Sanders <porkchop@invalid.foo> - 2026-01-02 19:44 +0000

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