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Re: Fix for Win32 division involving INT_MIN

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Magnus Hagander <mha(at)sollentuna(dot)net>, Wang Haiyong <wanghaiyong(at)neusoft(dot)com>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Fix for Win32 division involving INT_MIN
Date: 2006-06-12 16:09:12
Message-ID: 200606121609.k5CG9Ci07661@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-patches
Patch applied.  Backpatch to 8.1.X.

---------------------------------------------------------------------------


Bruce Momjian wrote:
> Tom Lane wrote:
> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > With no Win32 exception detection code in sight, I propose the following
> > > patch to prevent server crashes for unusual INT_MIN integer division. 
> > 
> > The overflow code tries hard to avoid assuming it knows what INT_MIN and
> > INT_MAX are --- this is maybe not so important for int4 but it is for
> > int8 (because of our support for int8-less machines).  I don't
> > immediately see how to make this test without assuming you know the
> > value of INT_MIN, but we ought to try to come up with one.
> > 
> > We do see funny behavior on Intel chips even without Windows, so it'd
> > be better to not #ifdef WIN32 but use the same overflow test for
> > everyone.
> 
> > I would imagine the same problem arises with int8, has anyone checked?
> 
> Seems int8 is OK on Win32:
> 
> 	postgres=# SELECT (-9223372036854775808) / (-1);
> 	ERROR:  bigint out of range
> 
> > Also, the overflow tests in the intNmul routines seem vulnerable.
> 
> I reproduced the crash using int4 multiplication.  Again int8
> multiplication seemed OK.
> 
> I tried int2 and that seemed OK.
> 
> Updated patch attached.
> 
> -- 
>   Bruce Momjian   http://candle.pha.pa.us
>   EnterpriseDB    http://www.enterprisedb.com
> 
>   + If your life is a hard drive, Christ can be your backup. +


> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
>        choose an index scan if your joining column's datatypes do not
>        match

-- 
  Bruce Momjian   http://candle.pha.pa.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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