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Re: Size of bool unspecified: why?

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From Ian Collins <ian-news@hotmail.com>
Newsgroups comp.lang.c++
Subject Re: Size of bool unspecified: why?
Date Thu, 21 Jul 2011 09:01:59 +1200
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On 07/21/11 08:46 AM, JBarleycorn wrote:
> James Kanze wrote:
>> On Jul 16, 6:02 pm, BGB<cr88...@hotmail.com>  wrote:
>>> On 7/16/2011 3:33 AM, MikeP wrote:
>>
>>>> Why is the size of 'bool' unspecified? That makes bools pretty
>>>> useless as struct members. If one foregoes bools in structs, why
>>>> not then specify that bools should be the size of int and thereby
>>>> likely to be fast to pass to and from functions? (Is it less
>>>> efficient to pass less-than-word-size integers because then they
>>>> have to be sign-extended or zero-extended, or any other reason?)
>>
>> First, is size of bool unspecified?  Or just implementation
>> defined?
>
> Isn't that the same thing?

Not in terms of the standard.  Implementation defined things have to be 
defined by the implementation.

>> The size of all types is implementation defined (with
>> a minimum size).
>>
>> And I don't see the issue with regards to structs.
>
> C compatibility where layout, then, matters? Data transfer/storage.

Then C++ added bool, C didn't have it so there was no layout 
compatibility to maintain.

>>> IIRC, many compilers default to making them the same size as char,
>>> or a single byte. this tends to be most convinient as, bigger, and
>>> they are just wasting space, and smaller, as messing with bits is
>>> awkward and costly (as well as compromising their direct
>>> addressability, ...).
>>
>> A bool is required to be addressable; sizeof(bool) is also
>> required to return an integral value.  So a bool can't be
>> smaller than a char.  On a byte addressable machine, there's
>> also no reason to make them bigger,
>
> Efficiency?

Maybe, but efficiency isn't only dependent on size.  If it were, we'd be 
using 64 bit ints on 64 bit machines.

-- 
Ian Collins

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Thread

Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-16 05:33 -0500
  Re: Size of bool unspecified: why? BGB <cr88192@hotmail.com> - 2011-07-16 10:02 -0700
    Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-20 13:05 -0700
      Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-20 15:46 -0500
        Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-21 09:01 +1200
          Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-20 19:32 -0500
            Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-21 14:46 +1200
              Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-20 23:28 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-21 16:43 +1200
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 02:56 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-21 20:19 +1200
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 18:29 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-22 11:40 +1200
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 22:33 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-22 15:46 +1200
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 23:07 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-22 16:12 +1200
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-31 18:45 +1200
                Re: Size of bool unspecified: why? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-22 00:12 -0700
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 11:10 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 16:52 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-23 09:55 +1200
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 11:01 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 17:17 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-23 10:46 +1200
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-24 03:48 -0700
                Re: Size of bool unspecified: why? Robert Wessel <robertwessel2@yahoo.com> - 2011-07-24 12:40 -0500
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-30 11:22 -0700
                Re: Size of bool unspecified: why? "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-07-31 02:33 +0200
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-30 11:34 -0700
                Re: Size of bool unspecified: why? "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-07-25 04:46 +0200
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-21 07:23 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 18:52 -0500
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 11:24 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 17:22 -0500
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-23 10:51 +1200
                Re: Size of bool unspecified: why? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-22 00:17 -0700
                Re: Size of bool unspecified: why? Robert Wessel <robertwessel2@yahoo.com> - 2011-07-22 04:26 -0500
            Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-21 02:09 -0700
              Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 19:11 -0500
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 11:58 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 17:48 -0500
            Re: Size of bool unspecified: why? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-21 08:41 -0700
              Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 19:14 -0500
                Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 12:01 -0700
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 17:51 -0500
        Re: Size of bool unspecified: why? Noah Roberts <dont@email.me> - 2011-07-20 16:57 -0700
          Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-21 07:29 -0700
            Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 19:24 -0500
              Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-22 12:33 +1200
                Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 22:42 -0500
        Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-21 01:59 -0700
          Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 19:42 -0500
            Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 12:20 -0700
              Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-22 18:21 -0500
  Re: Size of bool unspecified: why? Robert Wessel <robertwessel2@yahoo.com> - 2011-07-16 22:23 -0500
    Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-17 00:07 -0500
      Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-17 17:15 +1200
        Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-17 00:24 -0500
      Re: Size of bool unspecified: why? Robert Wessel <robertwessel2@yahoo.com> - 2011-07-17 02:02 -0500
        Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-17 03:02 -0500
          Re: Size of bool unspecified: why? Robert Wessel <robertwessel2@yahoo.com> - 2011-07-17 03:23 -0500
            Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-17 05:36 -0500
              Re: Size of bool unspecified: why? "James" <no@spam.invalid> - 2011-07-17 16:24 -0700
                Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-18 06:49 -0500
                Re: Size of bool unspecified: why? "James" <no@spam.invalid> - 2011-07-18 16:46 -0700
                Re: Size of bool unspecified: why? Ian Collins <ian-news@hotmail.com> - 2011-07-19 11:59 +1200
                Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-19 22:18 -0500
        Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-17 03:04 -0500
      Re: Size of bool unspecified: why? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-22 00:32 -0700
      Re: Size of bool unspecified: why? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-22 00:41 -0700
  Re: Size of bool unspecified: why? Juha Nieminen <nospam@thanks.invalid> - 2011-07-17 13:50 +0000
    Re: Size of bool unspecified: why? "MikeP" <mp011011@some.org> - 2011-07-18 06:50 -0500
      Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-20 13:06 -0700
    Re: Size of bool unspecified: why? Pawel Dziepak <pdziepak@quarnos.org> - 2011-07-21 12:59 +0000
      Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-21 07:11 -0700
        Re: Size of bool unspecified: why? "JBarleycorn" <jbnh2o@newsnet.org> - 2011-07-21 19:21 -0500
          Re: Size of bool unspecified: why? James Kanze <james.kanze@gmail.com> - 2011-07-22 12:28 -0700

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