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To: Channa <channa.kad@gmail.com>
From: Ian FREISLICH <ianf@clue.co.za>
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Date: Mon, 02 Feb 2009 15:48:29 +0200
Message-Id: <E1LTzA5-0005zc-OH@clue.co.za>
Cc: Christoph Mallon <christoph.mallon@gmx.de>, freebsd-current@freebsd.org
Subject: Re: Jemalloc SEGV for 1MB chunk 
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Channa wrote:
> Thanks for the reply.
> 
> I understand , after terminating the string with NULL character no
> SEGV is seen.
>
> But if i change the request size to a value less than 1MB for eg: 4096
> Bytes,
>
> I dont see any issues, without terminating the string with NULL
> character the test code works fine. The issue is seen only for size
> 1MB exactly.
>
> Can anyone explain this behaviour?

It's probably caused because although you asked for 4096 bytes of
memory a larger chunk was allocated so that a subsequent malloc calls
need not make a system call but can allocate from unallocated
allocated memory.  It's also likely that the memory was zeroed by
malloc so the string was NULL terminated "by accident".

Ian

--
Ian Freislich