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Re: Strange interval arithmetic

From: Michael Fuhr <mike(at)fuhr(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Strange interval arithmetic
Date: 2005-11-30 21:50:18
Message-ID: 20051130215018.GA24778@winnie.fuhr.org (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
On Wed, Nov 30, 2005 at 02:01:46PM -0500, Tom Lane wrote:
> Michael Fuhr <mike(at)fuhr(dot)org> writes:
> > Any preferences on an approach?  The simplest and easiest to verify
> > would be to raise an error for just this particular case; a TODO
> > item might be to change how the string is parsed to allow values
> > larger than LONG_MAX.
> 
> I think the latter would be a feature enhancement and therefore not
> good material to back-patch.  Just erroring out seems appropriate
> for now.

Agreed.  I'm thinking about rewriting strtol() calls in datetime.c
to look like this:

  errno = 0;
  val = strtol(field[i], &cp, 10);
  if (errno == ERANGE)
      return DTERR_FIELD_OVERFLOW;

Does that look okay?  Or would you rather raise an error with ereport()?

> > I see several calls to strtol() that aren't checked for overflow but
> > that might not be relevant to this problem, so I'm thinking this patch
> > ought not touch them.  Maybe that's another TODO item.
> 
> If it's possible for them to be given overflowing input, they probably
> ought to be checked.

I'm looking at all the strtol() calls in datetime.c right now; I
haven't looked anywhere else yet.  Should I bother checking values
that will be range checked later anyway?  Time zone displacements,
for example?

-- 
Michael Fuhr

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