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Re: “ChattyG takes a college freshman C/C++ programming exam”

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From Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups comp.lang.c++, comp.lang.c
Subject Re: “ChattyG takes a college freshman C/C++ programming exam”
Date Fri, 13 Oct 2023 10:04:31 -0700
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MarioCCCP <NoliMihiFrangereMentulam@libero.it> writes:
> On 08/10/23 21:31, Chris M. Thomasson wrote:
>> On 10/8/2023 4:22 AM, candycanearter07 wrote:
>>> On 10/8/23 04:55, Anton Shepelev wrote:
>>>> I disagree.  A function returns the value of its declared
>>>> return type.  And although C allows the definition of self-
>>>> referential structs, it does allow the declaration of self-
>>>> referencial functions.
>>>
>>> What if you typedef'd the function pointer?
>>>
>>> Also, you could probably get away with it by just setting it to a
>>> void pointer and casting the return value to the function pointer.
>> Not sure if that's allowed. A function pointer cast to a 
>> void pointer, which in turn is cast back to a function pointer is
>> undefined? What am I forgetting here?
>
> mine is not an answer but a doubt : maybe void * and void (*) (void)
> could require different alignment restrictions ?
>
> I dunno whether or not void * has any restriction at all ...

It does.

Object pointers can be converted to void* and back without loss of
information.  Quoting the C standard:

    A pointer to void may be converted to or from a pointer to any
    object type. A pointer to any object type may be converted to a
    pointer to void and back again; the result shall compare equal to
    the original pointer.

Function pointers can be converted to other function pointer types and
back again without loss of information.  Quoting the C standard again:

    A pointer to a function of one type may be converted to a pointer to
    a function of another type and back again; the result shall compare
    equal to the original pointer. If a converted pointer is used to
    call a function whose type is not compatible with the referenced
    type, the behavior is undefined.

But conversions between object pointer types (including void*) and
function pointer types have undefined behavior.

Many implementations do support meaningful conversion between function
pointer types and void* (and POSIX requires such conversions to work at
least for values returned by dlsym()).  On most implementations, all
pointers have the same representation, but that's not required.  A
conforming implementation could, for example, have 64-bit object
pointers and 128-bit function pointers.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */

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Thread

“ChattyG takes a college freshman C/C++ programming exam” Lynn McGuire <lynnmcguire5@gmail.com> - 2023-10-05 17:40 -0500
  Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-05 15:57 -0700
  Re: “ChattyG takes a college freshman C/C++ programming exam” Christian Gollwitzer <auriocus@gmx.de> - 2023-10-06 07:36 +0200
    Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-06 11:59 -0700
  Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-07 23:54 +0300
    Re: “ChattyG takes a college freshman C/C++ programming exam” jak <nospam@please.ty> - 2023-10-08 09:42 +0200
      Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-08 04:27 -0400
      Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-08 12:55 +0300
        Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-08 13:06 +0300
        Re: “ChattyG takes a college freshman C/C++ programming exam” candycanearter07 <no@thanks.net> - 2023-10-08 06:22 -0500
          Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-08 15:03 +0300
            Re: “ChattyG takes a college freshman C/C++ programming exam” Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2023-10-15 15:51 -0400
              Re: “ChattyG takes a college freshman C/C++ programming exam” Richard Damon <richard@damon-family.org> - 2023-10-15 17:53 -0400
              Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-16 00:07 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2023-10-16 22:01 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” Richard Damon <richard@damon-family.org> - 2023-10-16 22:41 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-17 12:22 -0400
          Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-08 12:31 -0700
            Re: “ChattyG takes a college freshman C/C++ programming exam” Richard Damon <news.x.richarddamon@xoxy.net> - 2023-10-08 21:17 -0400
              Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-09 01:13 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-10 12:18 -0700
            Re: “ChattyG takes a college freshman C/C++ programming exam” MarioCCCP <NoliMihiFrangereMentulam@libero.it> - 2023-10-13 11:22 +0200
              Re: “ChattyG takes a college freshman C/C++ programming exam” Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-10-13 10:04 -0700
        Re: “ChattyG takes a college freshman C/C++ programming exam” Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-10-08 13:54 +0100
        Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-08 11:25 -0400
          Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-08 20:07 +0300
        Re: “ChattyG takes a college freshman C/C++ programming exam” Blue-Maned_Hawk <bluemanedhawk@invalid.invalid> - 2023-10-08 16:37 +0000
          Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-08 20:05 +0300
            Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-09 01:13 -0400
              Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-09 13:30 -0700
                Re: Re: “ChattyG takes a college freshman C/C++ programming exam” scott@slp53.sl.home (Scott Lurndal) - 2023-10-09 20:33 +0000
                Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-10 12:04 -0700
            Re: “ChattyG takes a college freshman C/C++ programming exam” Blue-Maned_Hawk <bluemanedhawk@invalid.invalid> - 2023-10-09 12:17 +0000
              Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-09 23:03 +0300
                Re: “ChattyG takes a college freshman C/C++ programming exam” scott@slp53.sl.home (Scott Lurndal) - 2023-10-09 20:30 +0000
                Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-09 23:45 +0300
                Re: “ChattyG takes a college freshman C/C++ programming exam” scott@slp53.sl.home (Scott Lurndal) - 2023-10-09 21:21 +0000
                Re: “ChattyG takes a college freshman C/C++ programming exam” scott@slp53.sl.home (Scott Lurndal) - 2023-10-09 21:26 +0000
                Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-09 22:41 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-10-09 21:47 +0100
          Re: “ChattyG takes a college freshman C/C++ programming exam” Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-10-08 15:31 -0700
            Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-09 01:12 -0400
              Re: “ChattyG takes a college freshman C/C++ programming exam” Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-10-10 18:46 -0700
                Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-11 01:14 -0400
                Re: “ChattyG takes a college freshman C/C++ programming exam” scott@slp53.sl.home (Scott Lurndal) - 2023-10-11 13:47 +0000
                Re: “ChattyG takes a college freshman C/C++ programming exam” Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-10-11 07:56 -0700
            Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@gmail.moc> - 2023-10-09 23:06 +0300
              Re: “ChattyG takes a college freshman C/C++ programming exam” Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-10-09 17:15 -0700
      Re: “ChattyG takes a college freshman C/C++ programming exam” James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-10-08 11:08 -0400
  Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-11 21:06 -0700
    Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-11 21:10 -0700
    Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@g{oogle}mail.com> - 2023-10-12 10:56 +0300
    Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@g{oogle}mail.com> - 2023-10-12 10:57 +0300
      Re: “ChattyG takes a college freshman C/C++ programming exam” "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-10-12 12:59 -0700
  Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@g{oogle}mail.com> - 2023-10-12 10:53 +0300
    Re: “ChattyG takes a college freshman C/C++ programming exam” Phil Carmody <pc+usenet@asdf.org> - 2023-10-23 15:39 +0300
      Re: “ChattyG takes a college freshman C/C++ programming exam” Anton Shepelev <anton.txt@g{oogle}mail.com> - 2023-10-23 16:45 +0300

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