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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: "core C" |
| Date | 2015-07-01 08:05 -0700 |
| Organization | None to speak of |
| Message-ID | <lny4iz2a0i.fsf@kst-u.example.com> (permalink) |
| References | (6 earlier) <mmu7vc$eak$1@dont-email.me> <47f5d704-4ab6-4afc-a558-cbed67915a76@googlegroups.com> <mmugvp$mpc$1@dont-email.me> <8de0b72b-0f2c-45cc-92c7-0c3c498134e3@googlegroups.com> <mn0gap$cf3$1@dont-email.me> |
Bartc <bc@freeuk.com> writes:
> On 30/06/2015 18:04, Rick C. Hodgin wrote:
>> On Tuesday, June 30, 2015 at 12:45:08 PM UTC-4, Bart wrote:
>>> Presumably this (pointer,offset) combo is the same size overall as the
>>> other pointers in the language? Or would you make an exception, or not
>>> call it a pointer, or would require two values to be passed?
>>
>> Same size.
>
> I'm curious: how can a pointer and offset together be the same size as a
> pointer?
>
> Or do all pointers have a spare 32-bit field on the off-chance they
> might have to store an offset?
An example I've mentioned here many times: Cray vector machines are
word-oriented, where a word is 64 bits. A machine-level address/pointer
is a 64-bit quantity containing the address of a word. Cray's C
compiler has CHAR_BIT==8 (for Unix/POSIX compatibility), and implements
a byte pointer as a word pointer with the byte offset stored in the
otherwise unused high-order 3 bits.
Any system with 64-bit pointers that doesn't actually support 16
exabytes of memory is likely to be able to do something similar.
> (I also think that a normal byte-addressed pointer to a single value
> ought to be the same size regardless of the type it points to. But it is
> also reasonable that a bit pointer, bit-field pointer, slice, or
> bit/bitfield slice might all need extra information and could therefore
> be wider. You wouldn't then expect a void* type to accommodate all those
> special forms too.)
--
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"
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"core C" Rosario19 <Ros@invalid.invalid> - 2015-06-30 08:38 +0200
Re: "core C" jt@toerring.de (Jens Thoms Toerring) - 2015-06-30 07:54 +0000
Re: "core C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-30 02:55 -0700
Re: "core C" Rosario19 <Ros@invalid.invalid> - 2015-06-30 17:31 +0200
Re: "core C" Rosario19 <Ros@invalid.invalid> - 2015-06-30 18:15 +0200
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 12:19 -0700
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 04:27 -0700
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 04:48 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-06-30 13:07 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 05:15 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-06-30 13:02 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 05:13 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-06-30 13:58 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 06:11 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-06-30 15:11 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 07:50 -0700
Re: "core C" Rosario19 <Ros@invalid.invalid> - 2015-06-30 17:24 +0200
Re: "core C" Bartc <bc@freeuk.com> - 2015-06-30 17:44 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 10:04 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-07-01 11:46 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-01 04:40 -0700
Re: "core C" Keith Thompson <kst-u@mib.org> - 2015-07-01 08:05 -0700
Re: "core C" Bartc <bc@freeuk.com> - 2015-07-01 17:01 +0100
Re: "core C" Keith Thompson <kst-u@mib.org> - 2015-07-01 10:56 -0700
Re: "core C" BGB <cr88192@hotmail.com> - 2015-07-04 12:59 -0500
Re: "core C" Bartc <bc@freeuk.com> - 2015-07-04 20:25 +0100
Re: "core C" BGB <cr88192@hotmail.com> - 2015-07-04 20:56 -0500
Re: "core C" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-30 14:17 +0100
Re: "core C" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-30 14:03 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 06:16 -0700
Re: "core C" David Brown <david.brown@hesbynett.no> - 2015-06-30 15:46 +0200
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 07:54 -0700
Re: "core C" Steve Thompson <stevet810@gmail.com> - 2015-07-03 12:25 +0000
Re: "core C" jt@toerring.de (Jens Thoms Toerring) - 2015-07-01 15:04 +0000
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-01 08:12 -0700
Re: "core C" BGB <cr88192@hotmail.com> - 2015-07-04 10:36 -0500
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 04:41 -0700
Re: "core C" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-30 14:19 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 06:25 -0700
Re: "core C" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-30 15:48 +0100
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 07:52 -0700
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 04:42 -0700
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 08:28 -0700
Re: "core C" David Brown <david.brown@hesbynett.no> - 2015-06-30 22:28 +0200
Re: "core C" Ian Collins <ian-news@hotmail.com> - 2015-07-01 08:45 +1200
Re: "core C" "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-30 13:56 -0700
Re: "core C" David Brown <david.brown@hesbynett.no> - 2015-07-01 10:27 +0200
Re: "core C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-30 14:56 -0700
Re: "core C" Ian Collins <ian-news@hotmail.com> - 2015-07-01 10:03 +1200
Re: "core C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-30 15:31 -0700
Re: "core C" Ian Collins <ian-news@hotmail.com> - 2015-07-01 10:52 +1200
Re: "core C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-30 16:58 -0700
Re: "core C" Keith Thompson <kst-u@mib.org> - 2015-06-30 17:30 -0700
Re: "core C" David Brown <david.brown@hesbynett.no> - 2015-07-01 08:54 +0200
Re: "core C" Keith Thompson <kst-u@mib.org> - 2015-07-01 07:54 -0700
Re: "core C" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-01 09:42 -0700
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