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(a)minnie.tuhs.org &lt;tuhs-request(a)minnie.tuhs.org&gt; wrote: > Send TUHS mailing list submissions to > tuhs(a)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(a)minnie.tuhs.org > > You can reach the person managing the list at > tuhs-owner(a)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 &lt;david(a)kdbarto.org&gt; > To: tuhs(a)minnie.tuhs.org > Subject: [TUHS] Did realloc ever zero the new memory? > Message-ID: &lt;E798E102-2C50-4AB2-92CC-188D05AA951F(a)kdbarto.org&gt; > 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 &lt;jcapp(a)anteil.com&gt; > To: david(a)kdbarto.org > Cc: tuhs(a)minnie.tuhs.org > Subject: Re: [TUHS] Did realloc ever zero the new memory? > Message-ID: <5962857.12872.1441915841364.JavaMail.root@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" &lt;david(a)kdbarto.org&gt; > To: tuhs(a)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(a)minnie.tuhs.org > https://minnie.tuhs.org/mailman/listinfo/tuhs >