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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: arranging items in a array with a sorted pointer-list
Date: Sun, 06 Dec 2020 05:34:07 -0800
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James Kuyper <jameskuyper@alumni.caltech.edu> writes:

> On 12/2/20 9:53 AM, Ben Bacarisse wrote:
>
>> James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>
> ...
>
>>> I'm pretty tired right now, so maybe I'm missing something
>>> obvious.  If written in C, how would bsearch() go about returning
>>> a void* when it's arguments are const void*, without casting away
>>> const somewhere?

In English, the possessive form of "it" is spelled "its", with no
apostrophe.  The word "it's" is a contraction for "it is".

>> There are various ways, but as an old-timer,
>
> I definitely qualify as an old-time;  I remember what C was like
> before prototypes were added to the language.  They were an enormous
> improvement.

No one is suggesting otherwise.

>>  I like 
>>
>>   void *remove_const(s) void *s; { return s; }
>>
>> and in bsearch
>>
>>   return remove_const(ptr);
>
> I definitely don't like leaving out a function prototype,
> particularly when the only reason for doing so is to disable
> the type checking enabled by the prototype.

Here that isn't the only reason for not using a prototype, nor
even the most important reason.  A key point of not using a
prototype is so the call will have defined behavior.

However, if someone is determined never to use functions whose
declarations lack prototypes, that restriction too can be
accommodated:

  (file dequalify.h)

        #ifndef HAVE_DEQUALIFY_dot_H
        #define HAVE_DEQUALIFY_dot_H

        extern   void * dequalify( const volatile void * );

        #endif/*HAVE_DEQUALIFY_dot_H*/


  (file dequalify.c)

        #include "dequalify.h"

        #include <stdarg.h>

        static inline void *
        fixit( void *f( const volatile void * ), ... ){
            va_list a;  void *pv;

            va_start( a, f ),  pv = va_arg( a, void * ),  va_end( a );
            return  pv;
        }

        void *
        dequalify( const volatile void *x ){
            return  fixit( dequalify, x );
        }