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Groups > comp.lang.c > #63051

Re: counting bytes

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: counting bytes
Date 2015-06-07 23:49 +0200
Organization A noiseless patient Spider
Message-ID <ml2e69$e8i$1@dont-email.me> (permalink)
References (4 earlier) <cthalvFnjb7U1@mid.uni-berlin.de> <ml1h2m$1dc$1@dont-email.me> <87eglns3jc.fsf@kst-u.example.com> <ml2bjj$5jb$1@dont-email.me> <ml2cae$832$1@dont-email.me>

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On 07/06/15 23:17, Richard Heathfield wrote:
> On 07/06/15 22:05, David Brown wrote:
> 
> <snip>
> 
>> * I believe there may be a theoretical opening in the standards for an
>> architecture that has CHAR_BIT not equal to 8 and yet still has a
>> uint8_t type.  But I am certain that I will never be using such a system.
> 
> CHAR_BIT is guaranteed to be *at least* 8. If it is not 8, it must be
> greater than 8.
> 
> The sizeof operator yields a size_t, which is the size (in bytes) of its
> operand, and size_t has an unsigned integer type, which means that it
> cannot represent fractional sizes.
> 
> Since int8_t denotes a signed integer type with *exactly* 8 bits (see
> 7.20.1.1(1), which makes this crystal clear), on a system with CHAR_BIT
> greater than 8, it would have to have a fractional size.
> 
> Since the sizeof operator is both (a) required to yield the size in
> bytes of its operand, and (b) unable to yield the size of an int8_t on a
> system with CHAR_BIT > 8, we have a contradiction. I deduce that such an
> implementation would not be conforming.
> 

That all makes sense - but the C standards have this nasty tendency to
have weird loopholes hidden in them.  Just because neither you nor I see
a loophole here, doesn't mean there isn't one somewhere.  But it
certainly reduces the likelihood of a malicious ABI designer making a
target with uint8_t but CHAR_BIT != 8.

It is certainly possible for int8_t to exist but not be "signed char"
(by using an extended signed integer type with 8 bits) - perhaps that's
why I thought that there might be a loophole here too.

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counting bytes bilsch01 <king621@comcast.net> - 2015-06-06 04:58 -0700
  Re: counting bytes Bartc <bc@freeuk.com> - 2015-06-06 13:05 +0100
    Re: counting bytes bilsch01 <king621@comcast.net> - 2015-06-06 05:24 -0700
      Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-06 05:41 -0700
        Re: counting bytes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-06 14:00 +0100
      Re: counting bytes Bartc <bc@freeuk.com> - 2015-06-06 13:52 +0100
      Re: counting bytes Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-06-06 10:27 -0400
        Re: counting bytes jt@toerring.de (Jens Thoms Toerring) - 2015-06-06 22:31 +0000
          THANKS EVERYBODY FOR THE INFO bilsch01 <king621@comcast.net> - 2015-06-06 23:35 -0700
            Re: THANKS EVERYBODY FOR THE INFO Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-07 10:08 +0100
              Re: THANKS EVERYBODY FOR THE INFO Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-07 09:22 -0700
                Re: THANKS EVERYBODY FOR THE INFO Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-07 18:07 +0100
                Re: THANKS EVERYBODY FOR THE INFO Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-08 04:03 -0700
                Re: THANKS EVERYBODY FOR THE INFO Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 08:12 -0700
            Re: THANKS EVERYBODY FOR THE INFO Keith Thompson <kst-u@mib.org> - 2015-06-07 08:01 -0700
          Re: counting bytes gordonb.3gcai@burditt.org (Gordon Burditt) - 2015-06-07 05:02 -0500
          Re: counting bytes David Brown <david.brown@hesbynett.no> - 2015-06-07 15:32 +0200
            Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-06-07 12:48 -0700
              Re: counting bytes David Brown <david.brown@hesbynett.no> - 2015-06-07 23:05 +0200
                Re: counting bytes Richard Heathfield <rjh@cpax.org.uk> - 2015-06-07 22:17 +0100
                Re: counting bytes David Brown <david.brown@hesbynett.no> - 2015-06-07 23:49 +0200
                Re: counting bytes Richard Heathfield <rjh@cpax.org.uk> - 2015-06-07 23:37 +0100
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 08:25 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 08:21 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-11 13:54 -0500
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 06:33 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-20 09:51 -0500
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-24 09:49 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-24 12:26 -0500
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-30 11:16 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-30 23:15 -0500
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-02 06:07 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-02 14:31 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-09 05:31 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-09 17:09 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-05 09:58 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-09-05 19:29 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 14:38 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-09-06 17:46 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-07 23:50 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-09-06 22:00 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-07 23:24 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-24 20:03 -0400
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-24 22:13 -0500
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-25 02:22 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-25 11:39 -0500
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-25 09:48 -0700
                Re: counting bytes Martin Shobe <martin.shobe@yahoo.com> - 2015-07-25 14:04 -0500
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-25 14:22 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-25 11:07 -0400
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-25 12:43 -0400
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-25 13:32 -0400
                Re: counting bytes glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-25 20:14 +0000
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-25 17:24 -0400
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-25 14:42 -0700
                Re: counting bytes glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-25 23:02 +0000
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-25 19:17 -0400
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-25 16:37 -0700
                Re: counting bytes glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-26 06:10 +0000
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-26 08:31 -0400
                Re: counting bytes Bartc <bc@freeuk.com> - 2015-07-30 21:32 +0100
                Re: counting bytes raltbos@xs4all.nl (Richard Bos) - 2015-07-31 13:25 +0000
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-31 11:31 -0400
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-31 11:30 -0700
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-31 14:29 -0400
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-31 12:14 -0700
                Re: counting bytes David Kleinecke <dkleinecke@gmail.com> - 2015-07-31 17:39 -0700
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-31 23:32 -0400
                Re: counting bytes David Kleinecke <dkleinecke@gmail.com> - 2015-08-01 16:41 -0700
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-08-01 20:23 -0400
                Re: counting bytes Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-31 11:01 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-25 19:42 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-30 12:16 -0700
                Re: counting bytes Bartc <bc@freeuk.com> - 2015-07-30 22:04 +0100
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-02 06:10 -0700
                Re: counting bytes David Kleinecke <dkleinecke@gmail.com> - 2015-07-25 19:10 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-25 22:16 -0400
                Re: counting bytes David Kleinecke <dkleinecke@gmail.com> - 2015-07-25 19:46 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-30 11:52 -0700
                Re: counting bytes raltbos@xs4all.nl (Richard Bos) - 2015-07-31 08:51 +0000
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-02 06:19 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-01 09:39 -0400
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-08-01 13:06 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-01 20:43 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-02 06:52 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-02 15:14 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-09 07:54 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-08-09 16:43 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-05 10:48 -0700
                Re: counting bytes Richard Damon <Richard@Damon-Family.org> - 2015-07-11 17:50 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 06:36 -0700
                Re: counting bytes raltbos@xs4all.nl (Richard Bos) - 2015-07-20 15:14 +0000
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-24 09:38 -0700
                Re: counting bytes raltbos@xs4all.nl (Richard Bos) - 2015-07-25 19:12 +0000
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-30 12:18 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-11 17:03 -0700
                Re: counting bytes glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-12 00:15 +0000
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-11 17:42 -0700
                Re: counting bytes glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-12 02:46 +0000
                Re: counting bytes James Kuyper <jameskuyper@verizon.net> - 2015-07-12 12:33 -0400
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 06:48 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-20 11:18 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-24 09:58 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-24 11:14 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-30 11:02 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-07-30 13:10 -0700
                Re: counting bytes Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-01 10:53 -0700
                Re: counting bytes Keith Thompson <kst-u@mib.org> - 2015-06-07 14:46 -0700
                Re: counting bytes David Brown <david.brown@hesbynett.no> - 2015-06-08 09:05 +0200
  Re: counting bytes Siri Cruz <chine.bleu@yahoo.com> - 2015-06-06 05:06 -0700
  Re: counting bytes bartekltg <bartekltg@gmail.com> - 2015-07-26 00:58 +0200
    Re: counting bytes bartekltg <bartekltg@gmail.com> - 2015-07-26 01:00 +0200

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