Re: VMS

From	Robert Riches <spamtrap42@jacob21819.net>
Newsgroups	comp.os.linux.misc
Subject	Re: VMS
Date	2025-06-25 03:01 +0000
Organization	none-at-all
Message-ID	<slrn105mpkd.q0k.spamtrap42@one.localnet> (permalink)
References	(13 earlier) <mbmm2nFdsgcU2@mid.individual.net> <slrn105cajs.4vj.spamtrap42@one.localnet> <slrn105g20l.3q8n7.candycanearter07@candydeb.host.invalid> <slrn105k75h.h13.spamtrap42@one.localnet> <wwvpletmv3e.fsf@LkoBDZeT.terraraq.uk>

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On 2025-06-24, Richard Kettlewell <invalid@invalid.invalid> wrote:
> Robert Riches <spamtrap42@jacob21819.net> writes:
>> On 2025-06-22, candycanearter07
>> <candycanearter07@candycanearter07.nomail.afraid> wrote:
>>> Aren't you supposed to multiply by sizeof as well?
>>
>> Multiply by sizeof what?  sizeof(char)?  This was in the
>> pre-Unicode days.  Even now with Unicode, IIUC sizeof(char) is
>> still always 1.
>
> Yes. char is the unit in which sizeof measures things. Multiplying by
> ‘sizeof (char)’ is a completely incoherent thing to do.
>
> And as noted elsewhere, doing the multiplication yourself is generally
> the wrong approach.
>
>> IIUC, heap-based malloc _usually_ returns a larger allocation
>> block than you really asked for.
>
> Yes.
>
>> As long as malloc gave you at least 2 extra bytes, you'd never see any
>> misbehavior.  Even if it didn't give you 2 or more extra bytes, it's
>> fairly likely you'd just get lucky and never see the program crash or
>> otherwise misbehavior in a significant way.  For example, if you
>> stomped on the header of the next allocation block, as long as nothing
>> ever read and acted upon the data in said header, you'd never see it.
>
> This is wrong. Exceeding the space allocated by even 1 byte is undefined
> behavior, even if the allocation happens to have been sufficiently
> padded. What this means in practice is very situational but
> optimizations exploiting the freedom that undefined behavior provides to
> the compiler routinely result in defects.

Please remember that this was an unintended _BUG_ in some old
code, _NOT_ a deliberately chosen strategy.  What I was
describing was one possible explanation for how the bug remained
undetected for some number of years.

-- 
Robert Riches
spamtrap42@jacob21819.net
(Yes, that is one of my email addresses.)

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VMS c186282 <c186282@nnada.net> - 2025-06-14 01:15 -0400
  Re: VMS Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2025-06-14 10:05 -0700
    Re: VMS Andreas Eder <a_eder_muc@web.de> - 2025-06-14 20:30 +0200
      Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-14 23:27 +0000
        Re: VMS rbowman <bowman@montana.com> - 2025-06-15 00:57 +0000
          Re: VMS c186282 <c186282@nnada.net> - 2025-06-14 23:32 -0400
            Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-15 08:26 +0100
              Re: VMS c186282 <c186282@nnada.net> - 2025-06-15 21:12 -0400
                Re: VMS Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-06-16 18:15 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-17 23:20 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-18 04:14 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-18 02:34 -0400
            Re: VMS rbowman <bowman@montana.com> - 2025-06-15 18:49 +0000
              Re: VMS c186282 <c186282@nnada.net> - 2025-06-15 22:45 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-16 04:35 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-16 01:35 -0400
        Re: VMS c186282 <c186282@nnada.net> - 2025-06-14 23:03 -0400
          Re: VMS candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-06-18 05:30 +0000
            Re: VMS c186282 <c186282@nnada.net> - 2025-06-18 02:09 -0400
              Re: VMS candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-06-18 19:00 +0000
                Re: VMS Rich <rich@example.invalid> - 2025-06-18 20:23 +0000
                Re: VMS Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-06-18 20:30 +0000
                Re: VMS rbowman <bowman@montana.com> - 2025-06-18 23:09 +0000
              Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-19 08:40 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-20 00:43 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-20 09:00 +0100
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-20 10:19 +0100
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-20 15:15 +0100
                Re: VMS Rich <rich@example.invalid> - 2025-06-20 13:36 +0000
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-20 16:15 +0100
                Re: VMS Rich <rich@example.invalid> - 2025-06-20 23:07 +0000
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-21 01:07 +0100
                Re: VMS rbowman <bowman@montana.com> - 2025-06-21 03:09 +0000
                Re: VMS Robert Riches <spamtrap42@jacob21819.net> - 2025-06-21 03:43 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 01:36 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-21 05:53 +0000
                Re: VMS candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-06-22 13:50 +0000
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-22 15:27 +0100
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-22 15:56 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-23 00:18 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-22 19:23 +0000
                Re: VMS candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-06-23 18:10 +0000
                Re: VMS rbowman <bowman@montana.com> - 2025-06-23 19:27 +0000
                Re: VMS Robert Riches <spamtrap42@jacob21819.net> - 2025-06-24 03:34 +0000
                Re: VMS Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-06-24 04:52 +0000
                Re: VMS rbowman <bowman@montana.com> - 2025-06-24 05:14 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-24 01:36 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-24 06:49 +0000
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-24 10:31 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-25 01:36 -0400
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-25 07:31 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-25 03:08 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-24 08:56 +0100
                Re: VMS Robert Riches <spamtrap42@jacob21819.net> - 2025-06-25 03:01 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-25 01:59 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-25 06:52 +0000
                Re: VMS John Ames <commodorejohn@gmail.com> - 2025-06-25 09:32 -0700
                Re: VMS John Ames <commodorejohn@gmail.com> - 2025-06-25 09:44 -0700
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-25 19:01 -0400
                Re: VMS candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-06-27 06:00 +0000
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-27 08:37 +0100
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-27 08:45 +0100
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-27 08:14 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-27 13:27 -0400
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-27 19:13 +0100
                Re: VMS Chris Ahlstrom <OFeem1987@teleworm.us> - 2025-06-28 09:16 -0400
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-27 13:24 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-27 17:40 +0000
                Re: VMS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-06-27 18:20 +0000
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-27 23:03 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-28 01:13 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-28 06:10 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-27 18:16 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-28 08:52 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-28 23:16 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-29 08:18 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-29 19:09 -0400
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-30 08:36 +0100
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-30 08:51 +0100
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-30 08:59 +0100
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-30 08:33 +0000
                Re: VMS John Ames <commodorejohn@gmail.com> - 2025-06-30 09:08 -0700
                Re: VMS jayjwa <jayjwa@atr2.ath.cx.invalid> - 2025-06-30 22:18 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-30 09:00 +0100
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-30 09:24 +0100
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-30 08:34 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-30 23:30 -0400
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-30 23:26 -0400
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-07-01 10:49 +0100
                Re: VMS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-07-01 12:44 +0000
                Re: VMS Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-07-02 01:13 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-07-01 21:46 -0400
                Re: VMS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-07-02 16:03 +0000
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-30 07:54 +0000
                Re: VMS rbowman <bowman@montana.com> - 2025-06-30 18:10 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-30 23:12 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-07-01 04:02 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-07-01 12:42 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-30 08:56 +0100
                Re: VMS Rich <rich@example.invalid> - 2025-06-27 19:40 +0000
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-20 21:19 +0100
                Re: VMS Rich <rich@example.invalid> - 2025-06-20 23:17 +0000
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-21 08:42 +0100
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-21 07:02 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 03:23 -0400
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 01:27 -0400
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 01:10 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-21 05:59 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 02:10 -0400
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-20 10:12 +0100
                Re: VMS Rich <rich@example.invalid> - 2025-06-20 13:39 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 01:23 -0400
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-21 06:57 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 03:07 -0400
                Re: VMS Richard Kettlewell <invalid@invalid.invalid> - 2025-06-21 08:45 +0100
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-22 02:32 -0400
                Re: VMS Rich <rich@example.invalid> - 2025-06-20 13:30 +0000
                Re: VMS The Natural Philosopher <tnp@invalid.invalid> - 2025-06-20 16:14 +0100
                Re: VMS Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-06-20 08:57 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-21 01:17 -0400
    Re: VMS c186282 <c186282@nnada.net> - 2025-06-14 22:57 -0400
      Re: VMS Rich <rich@example.invalid> - 2025-06-15 14:24 +0000
        Re: VMS c186282 <c186282@nnada.net> - 2025-06-15 22:26 -0400
          Re: VMS rbowman <bowman@montana.com> - 2025-06-16 04:30 +0000
            Re: VMS c186282 <c186282@nnada.net> - 2025-06-16 01:31 -0400
            Re: VMS Rich <rich@example.invalid> - 2025-06-18 17:40 +0000
              Re: VMS rbowman <bowman@montana.com> - 2025-06-18 23:06 +0000
              Re: VMS c186282 <c186282@nnada.net> - 2025-06-18 19:43 -0400
                Re: VMS Rich <rich@example.invalid> - 2025-06-19 01:08 +0000
                Re: VMS c186282 <c186282@nnada.net> - 2025-06-19 00:46 -0400
                Re: VMS rbowman <bowman@montana.com> - 2025-06-19 06:36 +0000

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