[hobbit] overflow in netbsd-meminfo.c

Scott, Brian brian.scott4 at det.nsw.edu.au
Thu Nov 13 06:09:21 CET 2008


Isn't this a case of netbsd returning a perfectly valid number that
meminfo has misinterpreted as a negative number (-773). Hobbit has then
seen the negative number and incorrectly handled it as a very large
positive number.

Netbsd doesn't appear to have a bug based on this evidence.

Offcourse if netbsd is returning a negative number to meminfo then they
do have a bug. However, since the bug in the meminfo code could easily
have caused the error seen, we can't know if netbsd also has the same
bug. If the fix to meminfo works (and I'm guessing it does) then it's
pretty solid proof that there isn't an underlying problem in netbsd.

I don't have a copy of netbsd to double check this.

Regards,

Brian Scott

-----Original Message-----
From: Rich Smrcina [mailto:rsmrcina at wi.rr.com] 
Sent: Thursday, 13 November 2008 3:43 PM
To: hobbit at hswn.dk
Subject: Re: [hobbit] overflow in netbsd-meminfo.c

Tracy Di Marco White wrote:
>> That appears to be a bug in netbsd.
> 
> This is what it appears as in meminfo for one of my 4GB machines:
> [meminfo]
> Total:-773
> Free:2884
> Swaptotal:4098
> Swapused:0
> 
> Since freebsd-meminfo.c seems to be using unsigned long in the same
> place I modified it, I'm not sure it's a bug only in NetBSD.
> 

The display is a bug, Hobbit's interpretation and use of it is an
artifact of the bug.

If netbsd doesn't have a fix for this problem, you're patch is the right
solution.
-- 
Rich Smrcina
VM Assist, Inc.
Phone: 414-491-6001
Ans Service:  360-715-2467
http://www.linkedin.com/in/richsmrcina

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