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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle...
Date: Tue, 12 May 2015 10:05:30 -0700
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glen herrmannsfeldt <gah@ugcs.caltech.edu> writes:
> Tim Rentsch <txr@alumni.caltech.edu> wrote:
>> Keith Thompson <kst-u@mib.org> writes:
> (snip)
>>> You're right, size_t doesn't *necessarily* have to be a typedef.
>
> (snip)
>>> The only way to define size_t in standard C is to use a typedef --
>>> but standard headers aren't restricted to using standard C.  Using
>>> an extension would be permissible.
>
>>> I think it still has to be equivalent to some named predefined
>>> type.
>  
>> I agree that size_t must refer to a particular (ie, predefined)
>> type - if not a standard integer type then an extended integer
>> type.  I just don't find anything in the Standard that implies
>> that type has to have a name other than (in this case) size_t.
>> Why couldn't the name just be size_t?  There would need to be a
>> way to declare the name, but that could be done using a reserved
>> keyword or #pragma.
>
> OK, say, for example, a system where short is 16 bits, int
> and long are 32 bits. Also, consider that size_t
> might work just fine at 24 bits. 
>
> If 24 bits could be done faster than 32, it seems reasonable
> to use it.

Sure -- and one reasonable way to do that would be to define an
extended integer type, say `__int24`, and then have

    typedef size_t unsigned __int24;

in <stddef.h>.

But if 24-bit integers are faster than 32-bit integers, and are
useful for representing object sizes, it could also make sense to
make one of the standard integer types 24 bits (say, 16-bit short,
24-bit int, 32-bit long).  On the other hand, the limited number
of standard integer types might make that awkward.

-- 
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"