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Re: pointers

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From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: pointers
Date Mon, 24 Oct 2016 12:22:43 -0700
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supercat@casperkitty.com writes:
> On Monday, October 24, 2016 at 11:52:05 AM UTC-5, Keith Thompson wrote:
>> So the only reason you can think of to use those constructs is to
>> illustrate them?  That's hardly a good reason to add them to the
>> language.
>
> Especially on implementations where all pointers have the same representation
> and are alias-compatible with void*, it would be helpful to have a means by
> which a macro that wraps a function call could ensure that it is given a
> double-indirect pointer to some kind of object.  If the final target type
> were required to be something other than "void", such a macro could perhaps
> use:
>
>     foo(sizeof(**(theHandle)) >= 0 ? (void**)(theHandle) : 0));
>
> Since sizeof would not evaluate its operand, that would only cause theHandle
> to be evaluated once.  I can't think of any other way, though, to write a
> macro which would cast its argument to void** in the event that it was any
> kind of double-indirect pointer, but would squawk if it were anything else.

How is that relevant?  BartC is talking about constructs that are not
valid in C.  

(Of course void** is not a generic pointer-to-pointer type.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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pointers asetofsymbols@gmail.com - 2016-10-23 08:11 -0700
  Re: pointers Richard Heathfield <rjh@cpax.org.uk> - 2016-10-23 16:26 +0100
    Re: pointers asetofsymbols@gmail.com - 2016-10-23 10:35 -0700
      Re: pointers Ike Naar <ike@iceland.freeshell.org> - 2016-10-23 17:47 +0000
        Re: pointers asetofsymbols@gmail.com - 2016-10-25 12:55 -0700
      Re: pointers "James R. Kuyper" <jameskuyper@verizon.net> - 2016-10-23 13:58 -0400
        Re: pointers BartC <bc@freeuk.com> - 2016-10-24 00:55 +0100
          Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-23 17:27 -0700
            Re: pointers BartC <bc@freeuk.com> - 2016-10-24 11:53 +0100
              Re: pointers supercat@casperkitty.com - 2016-10-24 07:29 -0700
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 08:55 -0700
                Re: pointers Tim Rentsch <txr@alumni.caltech.edu> - 2016-10-24 14:02 -0700
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 14:42 -0700
                Re: pointers Tim Rentsch <txr@alumni.caltech.edu> - 2016-10-25 08:56 -0700
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 12:17 -0700
                Re: pointers Tim Rentsch <txr@alumni.caltech.edu> - 2016-10-26 06:37 -0700
              Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 08:49 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-24 17:25 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 09:52 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-24 18:15 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 12:20 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-24 20:58 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 13:16 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-24 23:53 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 13:38 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-25 23:06 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 15:39 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 00:26 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 16:44 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 01:02 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 17:35 -0700
                Re: pointers Ike Naar <ike@iceland.freeshell.org> - 2016-10-26 06:27 +0000
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 12:47 +0100
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-26 09:05 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 18:46 +0100
                Re: pointers supercat@casperkitty.com - 2016-10-26 11:44 -0700
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 20:12 +0100
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 20:30 +0100
                Re: pointers supercat@casperkitty.com - 2016-10-26 13:02 -0700
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-26 11:52 -0700
                Re: pointers Ike Naar <ike@iceland.freeshell.org> - 2016-10-26 19:11 +0000
                Re: pointers BartC <bc@freeuk.com> - 2016-10-26 21:25 +0100
                Re: pointers "James R. Kuyper" <jameskuyper@verizon.net> - 2016-10-25 18:56 -0400
                Re: pointers "James R. Kuyper" <jameskuyper@verizon.net> - 2016-10-25 19:12 -0400
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-25 16:31 -0700
                Re: pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-24 21:36 +0100
                Re: pointers BartC <bc@freeuk.com> - 2016-10-25 16:54 +0100
                Re: pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-25 19:09 +0100
                Re: pointers supercat@casperkitty.com - 2016-10-24 11:33 -0700
                Re: pointers Keith Thompson <kst-u@mib.org> - 2016-10-24 12:22 -0700
          Re: pointers James Kuyper <jameskuyper@verizon.net> - 2016-10-24 10:23 -0400
  Re: pointers "James R. Kuyper" <jameskuyper@verizon.net> - 2016-10-23 12:31 -0400
    Re: pointers Richard Heathfield <rjh@cpax.org.uk> - 2016-10-23 17:38 +0100
  Re: pointers Lorinczy Zsigmond <zsiga@nospam.for.me> - 2016-10-24 14:02 +0200
  Re: pointers John Bode <jfbode1029@gmail.com> - 2016-10-24 13:34 -0700

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