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Re: Do not cast pointers to functions to pointers to primitive types

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pacman@kosh.dhis.org (Alan Curry) writes:
> In article <lnharevbgq.fsf@nuthaus.mib.org>,
> Keith Thompson  <kst-u@mib.org> wrote:
>>pacman@kosh.dhis.org (Alan Curry) writes:
>>>
>>> Any idiot should be able to read that and know without being told that using
>>> a cast will get rid of the warning. Casts do that. It's obvious.
>>
> [...]
>>
>>I posted a code snippet upthread.  Here's a small complete program:
>>
>>    int main(void) {
>>        int obj;
>>        void *vp = &obj;
>>        void (*fp)(void) = (void (*)(void))vp; /* line 4 */
>>        return 0;
>>    }
>>
>>When I compile this with gcc 4.7, with "-pedantic" and any of
>>"-std={c90,c99,c11}", I get the following warning:
>>
>>    c.c:4:24: warning: ISO C forbids conversion of object pointer to
>>function pointer type [-pedantic]
>>
>>I get the same warning with or without the (void (*)(void)) cast.
>>(Without the cast, it's definitely a constraint violation.)
>>
>>You might want to reconsider your "Any idiot" statement.
>
> I reassert "idiot" in the direction of gcc then. Casts should be silent.

So you don't want to distinguish between casts whose behavior
is well defined, those whose behavior is implementation-defined,
and those whose behavior is completely undefined?

I can understand that opinion, but it hardly seems reasonable to
call those who disagrees with it idiots.

Casts are commonly interpreted to mean "Shut up, compiler, I know
what I'm doing"-- but the standard doesn't say or imply that.

How do you feel about casts applied to struct types, which are a
constraint violation?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Thread

Do not cast pointers to functions to pointers to primitive types ajaybgr <ajay.bgr@gmail.com> - 2012-09-03 01:50 -0700
  Re: Do not cast pointers to functions to pointers to primitive types Ian Collins <ian-news@hotmail.com> - 2012-09-03 20:59 +1200
  Re: Do not cast pointers to functions to pointers to primitive types Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-09-03 02:13 -0700
  Re: Do not cast pointers to functions to pointers to primitive types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-09-03 11:24 +0100
  Re: Do not cast pointers to functions to pointers to primitive types James Kuyper <jameskuyper@verizon.net> - 2012-09-03 08:31 -0400
    Re: Do not cast pointers to functions to pointers to primitive types Keith Thompson <kst-u@mib.org> - 2012-09-03 13:21 -0700
      Re: Do not cast pointers to functions to pointers to primitive types James Kuyper <jameskuyper@verizon.net> - 2012-09-03 16:57 -0400
        Re: Do not cast pointers to functions to pointers to primitive types Keith Thompson <kst-u@mib.org> - 2012-09-03 14:48 -0700
          Re: Do not cast pointers to functions to pointers to primitive types pacman@kosh.dhis.org (Alan Curry) - 2012-09-03 21:57 +0000
            Re: Do not cast pointers to functions to pointers to primitive types Keith Thompson <kst-u@mib.org> - 2012-09-03 18:11 -0700
              Re: Do not cast pointers to functions to pointers to primitive types pacman@kosh.dhis.org (Alan Curry) - 2012-09-04 02:03 +0000
                Re: Do not cast pointers to functions to pointers to primitive types Keith Thompson <kst-u@mib.org> - 2012-09-03 19:20 -0700
                Re: Do not cast pointers to functions to pointers to primitive types pacman@kosh.dhis.org (Alan Curry) - 2012-09-04 20:27 +0000
                Re: Do not cast pointers to functions to pointers to primitive types James Kuyper <jameskuyper@verizon.net> - 2012-09-04 17:10 -0400
                Re: Do not cast pointers to functions to pointers to primitive types Barry Schwarz <schwarzb@dqel.com> - 2012-09-04 14:14 -0700
          Re: Do not cast pointers to functions to pointers to primitive types pete <pfiland@mindspring.com> - 2012-09-03 22:51 -0400
      Re: Do not cast pointers to functions to pointers to primitive types Vincenzo Mercuri <vincenzo.mercuri@yahoo.it> - 2012-09-04 00:02 +0200
        Re: Do not cast pointers to functions to pointers to primitive types Keith Thompson <kst-u@mib.org> - 2012-09-03 18:19 -0700
  Re: Do not cast pointers to functions to pointers to primitive types Kaz Kylheku <kaz@kylheku.com> - 2012-09-04 01:18 +0000
    Re: Do not cast pointers to functions to pointers to primitive types "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2012-09-04 11:59 -0400
      Re: Do not cast pointers to functions to pointers to primitive types Philip Lantz <prl@canterey.us> - 2012-09-06 21:34 -0700

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