[TUHS] TUHS Digest, Vol 128, Issue 1

Rudi Blom rudi.j.blom at gmail.com
Fri Sep 11 16:21:28 AEST 2015 

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:
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> 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
>
> _______________________________________________
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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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