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Date: Wed, 28 Jan 2009 13:13:49 +0100
From: Rink Springer <rink@FreeBSD.org>
To: Channa <channa.kad@gmail.com>
Message-ID: <20090128121349.GJ16902@rink.nu>
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Cc: Christoph Mallon <christoph.mallon@gmx.de>, freebsd-current@freebsd.org
Subject: Re: Jemalloc SEGV for 1MB chunk
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Hi,

On Wed, Jan 28, 2009 at 05:31:43PM +0530, Channa wrote:
> size_t size = 1048576 ;
> 
>         buf = malloc(size);
>   for (i = 0; i <= 1048575; i++)
>     buf[i] = 'a';
> buf[size]='\0';
> printf("The length of buff is : %d\n",strlen(buf));
> free(buf);
> return 0;
> }
> 
> I NULL terminated the string
> buf[size] = '\0'  <== The last character is NULL
> 
> But still i get a SEGV at strlen.
> 
> Could you please tell me if my changes above are correct?

They are not - because size = 1048576, you will get a buffer of 1048576
bytes, that is, buf[0] ... buf[1048575] = buf[0] .. buf[size - 1]. Thus,
you need to do:

	buf[size - 1] = '\0';

And it'll work.
Regards,

-- 
Rink P.W. Springer                                - http://rink.nu
"Chance favours the prepared mind"
- Penn