[TUHS] TUHS Digest, Vol 128, Issue 1

Warner Losh imp at bsdimp.com
Fri Sep 11 23:17:09 AEST 2015 

When I ported OI to a few dozen OSes back in the early 1990s,
realloc behaved correctly. We used it in the pre-template / STL
days of C++ to implement variable length arrays. Any misbehavior
predated this.

The systems were HP/UX, AIX, AUX, OSF/1 (Digital Unix), SunOS 4,
Solaris, Linux, FreeBSD, IRIX, and Apollo's Unix.

Warner

On Fri, Sep 11, 2015 at 12:21 AM, Rudi Blom <rudi.j.blom at gmail.com> wrote:

> I never used realloc(), only malloc() and calloc().
>
> Checking a few unixes I have access to all reallocs() seem to state
> either nothing on contents of memory added or state explicitly
> 'undefined'.
>
> The only function which zeroes allocated memory is calloc() it seems.
> Unixes checks: SCO UNIX 3.2V4.2, Digital Unix 4.0G, Tru64 Unix V5.1B,
> HP-UX 11.23, HP-UX 11.31
>
> Cheers
>
> On 9/11/15, tuhs-request at minnie.tuhs.org <tuhs-request at minnie.tuhs.org>
> wrote:
> > Send TUHS mailing list submissions to
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> > than "Re: Contents of TUHS digest..."
> >
> >
> > Today's Topics:
> >
> >    1. Did realloc ever zero the new memory? (David)
> >    2. Re: Did realloc ever zero the new memory? (Jim Capp)
> >    3. Re: Did realloc ever zero the new memory? (David)
> >    4. Re: Did realloc ever zero the new memory? (Larry McVoy)
> >    5. Re: Did realloc ever zero the new memory? (David)
> >    6. Re: Did realloc ever zero the new memory? (Larry McVoy)
> >    7. Re: Did realloc ever zero the new memory? (Clem Cole)
> >    8. Re: Did realloc ever zero the new memory? (Dave Horsfall)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Thu, 10 Sep 2015 12:52:45 -0700
> > From: David <david at kdbarto.org>
> > To: tuhs at minnie.tuhs.org
> > Subject: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <E798E102-2C50-4AB2-92CC-188D05AA951F at kdbarto.org>
> > Content-Type: text/plain; charset=utf-8
> >
> > I?ve just had a discussion with my boss about this and he claimed that it
> > did at one point and I said it hasn?t in all the unix versions I?ve ever
> > played with (v6, v7, sys III, V, BSD 2, 3, 4, SunOS and Solaris).
> >
> > My question to this illustrious group is: Did any Unix or Unix like OS
> ever
> > zero fill on realloc?
> >
> >       David
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Thu, 10 Sep 2015 16:10:41 -0400 (EDT)
> > From: Jim Capp <jcapp at anteil.com>
> > To: david at kdbarto.org
> > Cc: tuhs at minnie.tuhs.org
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <5962857.12872.1441915841364.JavaMail.root at zimbraanteil>
> > Content-Type: text/plain; charset="utf-8"
> >
> > On every system that I've ever used, I believe that realloc did not do a
> > zero fill. There might have been a time when malloc did a zero fill, but
> I
> > never counted on it. I always performed a memset or bzero after a malloc.
> > I'm pretty sure that I counted on realloc to NOT perform a zero fill.
> >
> >
> > $.02
> >
> >
> >
> > From: "David" <david at kdbarto.org>
> > To: tuhs at minnie.tuhs.org
> > Sent: Thursday, September 10, 2015 3:52:45 PM
> > Subject: [TUHS] Did realloc ever zero the new memory?
> >
> > I?ve just had a discussion with my boss about this and he claimed that it
> > did at one point and I said it hasn?t in all the unix versions I?ve ever
> > played with (v6, v7, sys III, V, BSD 2, 3, 4, SunOS and Solaris).
> >
> > My question to this illustrious group is: Did any Unix or Unix like OS
> ever
> > zero fill on realloc?
> >
> > David
> >
> > _______________________________________________
> > TUHS mailing list
> > TUHS at minnie.tuhs.org
> > https://minnie.tuhs.org/mailman/listinfo/tuhs
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> >
> > ------------------------------
> >
> > Message: 3
> > Date: Thu, 10 Sep 2015 13:22:33 -0700
> > From: David <david at kdbarto.org>
> > To: Larry McVoy <lm at mcvoy.com>
> > Cc: tuhs at minnie.tuhs.org
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <395F25EB-77F3-4830-A1AF-C27E43550C04 at kdbarto.org>
> > Content-Type: text/plain; charset=us-ascii
> >
> > Buggy, sure.
> >
> > Zero (less) filling, that is the question.
> >
> > Realloc has had a difficult history, and I try to avoid it if at all
> > possible.
> >
> >       David
> >
> >> On Sep 10, 2015, at 1:21 PM, Larry McVoy <lm at mcvoy.com> wrote:
> >>
> >> Am I the only one that remembers realloc() being buggy on some systems?
> >
> >
> >
> > ------------------------------
> >
> > Message: 4
> > Date: Thu, 10 Sep 2015 13:27:23 -0700
> > From: Larry McVoy <lm at mcvoy.com>
> > To: David <david at kdbarto.org>
> > Cc: tuhs at minnie.tuhs.org
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <20150910202723.GI8154 at mcvoy.com>
> > Content-Type: text/plain; charset=us-ascii
> >
> > Good, glad to know it wasn't just me.  I've finally let my team use it
> > but we avoided it when we supported more odd ball platforms.
> >
> > On zero fill, I doubt many did that.  Many really early on when memory
> > was small.
> >
> > What you might be thinking of is modern systems implement malloc()
> > as an mmap of /dev/zero and the initial data comes through as zeroed.
> > But counting on that would be a mistake.
> >
> > On Thu, Sep 10, 2015 at 01:22:33PM -0700, David wrote:
> >> Buggy, sure.
> >>
> >> Zero (less) filling, that is the question.
> >>
> >> Realloc has had a difficult history, and I try to avoid it if at all
> >> possible.
> >>
> >>      David
> >>
> >> > On Sep 10, 2015, at 1:21 PM, Larry McVoy <lm at mcvoy.com> wrote:
> >> >
> >> > Am I the only one that remembers realloc() being buggy on some
> systems?
> >
> > --
> > ---
> > Larry McVoy                        lm at mcvoy.com
> > http://www.mcvoy.com/lm
> >
> >
> > ------------------------------
> >
> > Message: 5
> > Date: Thu, 10 Sep 2015 13:29:16 -0700
> > From: David <david at kdbarto.org>
> > To: Larry McVoy <lm at mcvoy.com>
> > Cc: tuhs at minnie.tuhs.org
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <FF64BDD6-C57E-4959-B0D1-2F97FF909EA9 at kdbarto.org>
> > Content-Type: text/plain; charset=utf-8
> >
> > I mentioned the /dev/zero malloc and, no, he was quite sure that it was
> > realloc doing the zero fills.
> >
> > Glad to know that I?m sitting on the right side of history on this one.
> >
> >       David
> >
> >> On Sep 10, 2015, at 1:27 PM, Larry McVoy <lm at mcvoy.com> wrote:
> >>
> >> Good, glad to know it wasn't just me.  I've finally let my team use it
> >> but we avoided it when we supported more odd ball platforms.
> >>
> >> On zero fill, I doubt many did that.  Many really early on when memory
> >> was small.
> >>
> >> What you might be thinking of is modern systems implement malloc()
> >> as an mmap of /dev/zero and the initial data comes through as zeroed.
> >> But counting on that would be a mistake.
> >>
> >> On Thu, Sep 10, 2015 at 01:22:33PM -0700, David wrote:
> >>> Buggy, sure.
> >>>
> >>> Zero (less) filling, that is the question.
> >>>
> >>> Realloc has had a difficult history, and I try to avoid it if at all
> >>> possible.
> >>>
> >>>     David
> >>>
> >>>> On Sep 10, 2015, at 1:21 PM, Larry McVoy <lm at mcvoy.com> wrote:
> >>>>
> >>>> Am I the only one that remembers realloc() being buggy on some
> systems?
> >>
> >> --
> >> ---
> >> Larry McVoy                       lm at mcvoy.com
> >> http://www.mcvoy.com/lm
> >
> >
> >
> > ------------------------------
> >
> > Message: 6
> > Date: Thu, 10 Sep 2015 13:21:15 -0700
> > From: Larry McVoy <lm at mcvoy.com>
> > To: Jim Capp <jcapp at anteil.com>
> > Cc: tuhs at minnie.tuhs.org, david at kdbarto.org
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <20150910202115.GH8154 at mcvoy.com>
> > Content-Type: text/plain; charset=us-ascii
> >
> > Am I the only one that remembers realloc() being buggy on some systems?
> >
> >
> > ------------------------------
> >
> > Message: 7
> > Date: Thu, 10 Sep 2015 16:41:26 -0400
> > From: Clem Cole <clemc at ccc.com>
> > To: Larry McVoy <lm at mcvoy.com>
> > Cc: david at kdbarto.org, TUHS main list <tuhs at minnie.tuhs.org>
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID:
> >       <
> CAC20D2P_Gw-YKP8EHASFToTe_W0nfdcJabQ6_aJYnX0BhnPvng at mail.gmail.com>
> > Content-Type: text/plain; charset="utf-8"
> >
> > below
> >
> > On Thu, Sep 10, 2015 at 4:21 PM, Larry McVoy <lm at mcvoy.com> wrote:
> >
> >> Am I the only one that remembers realloc() being buggy on some systems?
> >>
> >>
> > ?Amen...   it was rarely useful.   I always found realloc to one of the
> > part I could never trust.  I do remember  what you got back from any of
> the
> > malloc calls could vary widely.  Particularly pre-ANSI C and working on
> > non-UNIX systems.
> >
> >
> > Malloc in general was always a tarbaby because there were (are) so many
> > implementations "in the wild."   I used to advise our application people
> to
> > create something that was application specific and then call the local
> > malloc under the covers, but the chances that a general malloc
> > implementation would be optimal for your code was low.?
> >
> > Clem
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> >
> > ------------------------------
> >
> > Message: 8
> > Date: Fri, 11 Sep 2015 10:13:41 +1000 (EST)
> > From: Dave Horsfall <dave at horsfall.org>
> > To: The Eunuchs Hysterical Society <tuhs at tuhs.org>
> > Subject: Re: [TUHS] Did realloc ever zero the new memory?
> > Message-ID: <alpine.BSF.2.11.1509111005190.42450 at aneurin.horsfall.org>
> > Content-Type: text/plain; charset="utf-8"
> >
> > On Thu, 10 Sep 2015, David wrote:
> >
> >> I?ve just had a discussion with my boss about this and he claimed that
> >> it did at one point and I said it hasn?t in all the unix versions I?ve
> >> ever played with (v6, v7, sys III, V, BSD 2, 3, 4, SunOS and Solaris).
> >
> > Only V6?  I did V5...  Tell that to the young kids of today, and they
> > won't believe you.
> >
> >> My question to this illustrious group is: Did any Unix or Unix like OS
> >> ever zero fill on realloc?
> >
> > Never in my lifetime, which meant that you got inspect someone's private
> > messages and there's someone knocking at my door and
> >
> > #$%^&*\{{{
> >
> > NO CARRIER
> >
> > ------------------------------
> >
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> >
> >
> > End of TUHS Digest, Vol 128, Issue 1
> > ************************************
> >
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