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From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.unix.questions
Subject: Re: sbrk(2) question
Message-ID: <6582@auspex.auspex.com>
Date: 12 Mar 91 18:56:18 GMT
References: <1991Mar8.180132.12025@Think.COM> <4296@skye.ed.ac.uk>
Organization: Auspex Systems, Santa Clara
Lines: 11

>There's one case where it amlost certainly won't be zero, which is when
>memory has been previously alocated and released (eg by calling sbrk()
>with a negative argument).  So it's unwise to rely on it even if the
>operating system allocates zeroed (or zero-fill-when-referenced) pages.

Umm, why would it not be zero in that situation?  If the memory has
truly been released, as in "handed back to the kernel", it should be
re-zeroed if allocated to a process again.  (I.e., calling "sbrk()" with
a negative argument, in most if not all versions of UNIX, doesn't just
set some user-mode pointer so that the memory stays in the address space
of the process.)