From mboxrd@z Thu Jan 1 00:00:00 1970 From: imp@bsdimp.com (Warner Losh) Date: Fri, 11 Sep 2015 07:17:09 -0600 Subject: [TUHS] TUHS Digest, Vol 128, Issue 1 In-Reply-To: References: Message-ID: 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 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 > wrote: > > Send TUHS mailing list submissions to > > tuhs at minnie.tuhs.org > > > > To subscribe or unsubscribe via the World Wide Web, visit > > https://minnie.tuhs.org/mailman/listinfo/tuhs > > or, via email, send a message with subject or body 'help' to > > tuhs-request at minnie.tuhs.org > > > > You can reach the person managing the list at > > tuhs-owner at minnie.tuhs.org > > > > When replying, please edit your Subject line so it is more specific > > 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 > > To: tuhs at minnie.tuhs.org > > Subject: [TUHS] Did realloc ever zero the new memory? > > Message-ID: > > 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 > > 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" > > 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 > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > > < > http://minnie.tuhs.org/pipermail/tuhs/attachments/20150910/f4857c45/attachment-0001.html > > > > > > ------------------------------ > > > > Message: 3 > > Date: Thu, 10 Sep 2015 13:22:33 -0700 > > From: David > > To: Larry McVoy > > 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 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 > > To: David > > 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 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 > > To: Larry McVoy > > Cc: tuhs at minnie.tuhs.org > > Subject: Re: [TUHS] Did realloc ever zero the new memory? > > Message-ID: > > 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 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 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 > > To: Jim Capp > > 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 > > To: Larry McVoy > > Cc: david at kdbarto.org, TUHS main list > > 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 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 > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > > < > http://minnie.tuhs.org/pipermail/tuhs/attachments/20150910/25a3e14c/attachment-0001.html > > > > > > ------------------------------ > > > > Message: 8 > > Date: Fri, 11 Sep 2015 10:13:41 +1000 (EST) > > From: Dave Horsfall > > To: The Eunuchs Hysterical Society > > Subject: Re: [TUHS] Did realloc ever zero the new memory? > > Message-ID: > > 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 > > > > ------------------------------ > > > > _______________________________________________ > > TUHS mailing list > > TUHS at minnie.tuhs.org > > https://minnie.tuhs.org/mailman/listinfo/tuhs > > > > > > End of TUHS Digest, Vol 128, Issue 1 > > ************************************ > > > _______________________________________________ > TUHS mailing list > TUHS at minnie.tuhs.org > https://minnie.tuhs.org/mailman/listinfo/tuhs > -------------- next part -------------- An HTML attachment was scrubbed... URL: