Re: Pointer Arithmetic & UB

From	glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: Pointer Arithmetic & UB
Date	2013-01-18 20:59 +0000
Organization	Aioe.org NNTP Server
Message-ID	<kdcd4d$10i$1@speranza.aioe.org> (permalink)
References	(4 earlier) <kfnhamhblwo.fsf@x-alumni2.alumni.caltech.edu> <0.ee0ca3b7f0127d4ae325.20130116153452GMT.87wqvd9m5f.fsf@bsb.me.uk> <kfnsj619e49.fsf@x-alumni2.alumni.caltech.edu> <kd6tt1$l5$1@speranza.aioe.org> <kfny5fq8fta.fsf@x-alumni2.alumni.caltech.edu>

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Tim Rentsch <txr@alumni.caltech.edu> wrote:
> glen herrmannsfeldt <gah@ugcs.caltech.edu> writes:

>> Tim Rentsch <txr@alumni.caltech.edu> wrote:
>> [snip]

>>> and implementations aren't allowed to assume something (like
>>> what side effects are caused by some volatile access) that the
>>> Standard deems outside of what they know.
>
>> This is the one I don't agree with.  An implementation might, for
>> example, and as an extension, allow access to I/O registers.  The
>> implementation might, then, document that I/O registers should be
>> declared volatile, and might even document that no other kinds of
>> volatile data are supported.

> Implementations don't get to make that choice.  The volatile
> keyword is allowed in declaring/defining any variable, and also
> in type names (eg, casts or compound literals).  Any expression
> doing an access through a volatile-qualified lvalue is obliged to
> perform that access under the rules that the Standard gives for
> the semantics of such accesses.  Implementations don't get to
> choose which volatile-qualified accesses are "supported" and
> which ones aren't -- the Standard obliges them to perform them
> all, and without making any assumptions about what side effects
> might take place as a result.

I don't say this very often, but that is just dumb.

Except for the case of multithreading, which has been pretty
much left out of the discussion, only the implementation knows
which possible accesses need to be protected against, and how
to protect against them.

Someone whose name I forget used to post in comp.lang.fortran
on how useless the C rules were for volatile, but I never
understood why they were so useless.

Now, on many processors with memory mapped I/O registers,
it is simple to access one by dereferencing a pointer
to a specific address. Volatile pointers and pointers
(that aren't volatile) to volatile locations also have
been pretty much left out of the discussion.

>>> What constitutes an access to a volatile object is
>>> implementation defined, but what happens when a volatile
>>> access occurs is not, and cannot be,

>> Why can't the implementation define exactly what types of
>> volatile access it allows?

> Because it isn't consistent with the requirements that all
> accesses be performed, and volatile-qualified accesses be
> performed according to how the Standard describes the semantics
> for such accesses.

There are way too many different ways to access memory, most
of which only the implementation can know about.

OK, say a program has:

volatile int x=1;
while(x) ;

waiting until someone, somewhere, changes x, and, as
required the implementation makes the appropriate access and, among
others, doesn't optimize the loop. Now, say that the implementation
has a cache such that, even though memory fetch instructions are
executed it never actually gets to real memory. Maybe the user need
to go to the BIOS setup and turn off caching. Yet you say that
the standard understands how to do that?

>>> defined by an implementation, because the Standard specifically
>>> allows side effects unknown to the implementation to take place,
>>> and implementations are obliged to proceed under that assumption.

>> OK, then, the implementation can, as an extension to the standard,
>> define which types of volatile access it allow and which ones it
>> doesn't.  [snip]

> That simply isn't consistent with what the Standard requires.
> Implementations must carry out volatile-qualified accesses
> according to the requireed semantics;  they don't get to choose
> which of those might be "allowed" and which aren't.  It's like
> saying an implementation could define an extension where array
> indexing only works for even index values -- it cannot, because
> such an implementation fails to meet the requirements that the
> Standard otherwise imposes.

Probably a bad example because, with alignment restrictions, 
implementations can do just that. The implementation has to
add the appropriate padding, as required. 

Fortran now has the ASYNCHRONOUS attribute, and ASYNCHRONOUS I/O
statements. That is another way that variables can change at
unexpected times. I know I used asynchronous I/O in SunOS C
many years ago, but it wasn't in the standard, and may still
not be. 

I previously wrote about the PL/I ABNORMAL attribute. PL/I is
insteresting as, pretty much, the whole language was defined
before any implementations were written. They had to anticipate
what could and couldn't be implemented, and ABNORMAL has a 
pretty simple definition. But it is then up to the implementation
to figure out what can actually happen, and what to do about it.

-- glen

Thread

Pointer Arithmetic & UB Edward Rutherford <edward.p.rutherford79@REMOVETHIS.gmail.com> - 2012-12-10 17:14 +0000
  Re: Pointer Arithmetic & UB "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-12-10 09:35 -0800
  Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-10 12:55 -0500
    Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-10 13:25 -0500
      Re: Pointer Arithmetic & UB falk@rahul.net (Edward A. Falk) - 2012-12-11 00:46 +0000
        Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-10 21:28 -0500
          Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-12 14:36 -0500
            Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-12 20:35 +0000
            Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-12 15:57 -0500
            Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-12 16:02 -0500
              Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-12 16:13 -0500
                Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-12 21:18 -0500
                Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-12 22:42 -0500
                Re: Pointer Arithmetic & UB Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-17 12:04 +0200
                Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-17 08:47 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-17 14:58 +0000
                Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-17 10:59 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-17 17:26 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-17 19:33 -0500
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-20 11:00 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-20 10:03 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-20 22:02 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-21 13:09 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-21 22:40 +0000
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-21 23:39 -0500
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-22 06:50 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-22 00:15 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-22 10:34 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-22 09:32 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-23 09:38 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-23 09:55 -0800
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-26 13:35 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-27 09:03 -0800
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-27 21:31 -0500
                Re: Pointer Arithmetic & UB Philip Lantz <prl@canterey.us> - 2012-12-28 01:55 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-29 13:43 -0800
                Re: Pointer Arithmetic & UB Philip Lantz <prl@canterey.us> - 2012-12-28 01:39 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-28 11:31 +0000
                Re: Pointer Arithmetic & UB Keith Thompson <kst-u@mib.org> - 2012-12-28 08:47 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-29 17:45 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-30 04:06 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-02 10:08 -0800
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-26 13:29 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-27 07:55 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-27 08:01 -0800
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-27 21:10 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-29 18:03 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-23 03:48 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-23 10:22 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-27 10:34 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-27 10:16 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-10 17:26 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-12 12:38 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-12 20:50 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-13 13:07 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-13 22:11 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-14 11:11 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-12 18:32 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-13 00:34 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-13 16:40 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-14 00:01 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-13 19:20 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-14 01:03 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-13 20:41 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-14 03:19 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-13 23:36 -0500
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-13 23:43 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-14 13:20 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-14 20:02 -0500
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-15 21:20 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-14 10:23 -0800
                Re: Pointer Arithmetic & UB 88888 Dihedral <dihedral88888@googlemail.com> - 2013-01-15 10:53 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-15 22:39 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-15 22:28 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-15 23:35 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-16 23:38 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-18 09:37 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-14 10:29 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-15 21:38 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-15 23:57 -0800
                Re: Pointer Arithmetic & UB Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-16 15:34 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-16 11:15 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-16 10:28 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-16 19:09 +0000
                Re: Pointer Arithmetic & UB Richard Damon <news.x.richarddamon@xoxy.net> - 2013-01-16 23:26 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-18 10:08 -0800
                Re: Pointer Arithmetic & UB Keith Thompson <kst-u@mib.org> - 2013-01-18 11:33 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-18 14:00 -0800
                Re: Pointer Arithmetic & UB Richard Damon <news.x.richarddamon@xoxy.net> - 2013-01-19 09:10 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-20 13:35 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-20 20:15 -0500
                Re: Pointer Arithmetic & UB Richard Damon <news.x.richarddamon@xoxy.net> - 2013-01-20 21:05 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-21 09:43 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-18 11:13 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-18 20:59 +0000
                Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2013-01-18 16:24 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-19 00:17 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-19 11:22 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-20 14:51 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-21 00:07 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-21 10:05 -0800
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-21 20:19 +0000
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-21 23:20 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2013-01-18 17:48 -0500
                Re: Pointer Arithmetic & UB 88888 Dihedral <dihedral88888@googlemail.com> - 2013-01-18 13:13 -0800
                Re: Pointer Arithmetic & UB Robert Wessel <robertwessel2@yahoo.com> - 2012-12-20 12:21 -0600
                Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-20 13:40 -0500
                Re: Pointer Arithmetic & UB Robert Wessel <robertwessel2@yahoo.com> - 2012-12-20 13:32 -0600
                Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-20 14:58 -0500
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-20 21:54 +0000
                Re: Pointer Arithmetic & UB Lanarcam <lanarcam1@yahoo.fr> - 2012-12-20 19:49 +0100
                Re: Pointer Arithmetic & UB Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-21 02:38 +0200
                Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-21 14:33 -0500
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-21 03:18 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-21 13:16 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-21 17:57 -0500
                Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-21 23:52 +0000
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-21 19:47 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-21 22:54 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-22 03:31 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-22 09:16 -0800
                Re: Pointer Arithmetic & UB Shao Miller <sha0.miller@gmail.com> - 2012-12-24 04:23 -0500
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-27 11:07 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 02:33 -0800
                Re: Pointer Arithmetic & UB Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 02:18 -0800
        Re: Pointer Arithmetic & UB Noob <root@127.0.0.1> - 2012-12-11 11:36 +0100
          Re: Pointer Arithmetic & UB "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-12-11 10:00 -0800
            Re: Pointer Arithmetic & UB Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-17 12:11 +0200
        Re: Pointer Arithmetic & UB Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-11 15:27 -0500
          Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-11 21:09 +0000
        Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-12 14:30 -0500
          Re: Pointer Arithmetic & UB Keith Thompson <kst-u@mib.org> - 2012-12-12 11:42 -0800
          Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-12 17:12 -0500
          Re: Pointer Arithmetic & UB Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-17 12:16 +0200
  Re: Pointer Arithmetic & UB Prathamesh Kulkarni <bilbotheelffriend@gmail.com> - 2012-12-10 12:04 -0800
    Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-10 15:29 -0500
      Re: Pointer Arithmetic & UB Prathamesh Kulkarni <bilbotheelffriend@gmail.com> - 2012-12-10 12:44 -0800
        Re: Pointer Arithmetic & UB Prathamesh Kulkarni <bilbotheelffriend@gmail.com> - 2012-12-10 12:47 -0800
          Re: Pointer Arithmetic & UB James Kuyper <jameskuyper@verizon.net> - 2012-12-10 16:02 -0500
            Re: Pointer Arithmetic & UB Prathamesh Kulkarni <bilbotheelffriend@gmail.com> - 2012-12-10 13:08 -0800
              Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-12 14:26 -0500
            Re: Pointer Arithmetic & UB Greg Martin <greg@softsprocket.com> - 2012-12-10 14:55 -0800
        Re: Pointer Arithmetic & UB Sjouke Burry <s@b> - 2012-12-10 21:18 +0000
        Re: Pointer Arithmetic & UB falk@rahul.net (Edward A. Falk) - 2012-12-11 00:48 +0000
      Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-10 21:01 +0000
      Re: Pointer Arithmetic & UB Ken Brody <kenbrody@spamcop.net> - 2012-12-12 14:24 -0500
        Re: Pointer Arithmetic & UB Robert Wessel <robertwessel2@yahoo.com> - 2012-12-12 14:34 -0600
        Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-12 20:45 +0000
          Re: Pointer Arithmetic & UB Robert Wessel <robertwessel2@yahoo.com> - 2012-12-12 15:29 -0600
            Re: Pointer Arithmetic & UB glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-13 02:02 +0000
        Re: Pointer Arithmetic & UB Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-12-17 05:57 -0800
    Re: Pointer Arithmetic & UB pete <pfiland@mindspring.com> - 2012-12-10 20:20 -0500

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