Horton

Re: Greatest Common Divisor

Vik Fearing <vik.fearing@2ndquadrant.com>

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From: Vik Fearing <vik.fearing@2ndquadrant.com>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Fabien COELHO <coelho@cri.ensmp.fr>, Stephen Frost <sfrost@snowman.net>, Chapman Flack <chap@anastigmatix.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-01-26T05:52:05Z
Lists: pgsql-hackers 
On 25/01/2020 15:18, Dean Rasheed wrote:
> 
> Committed with some adjustments, mostly cosmetic but a couple more substantive:

Thanks!

> The code to guard against a floating point exception with inputs of
> (INT_MIN, -1) wasn't quite right because it actually just moved the
> problem so that it would fall over with inputs of (INT_MIN, +1).

Good catch.

> The convention in numeric.c is that the xxx_var() functions take
> *pointers* to their NumericVar arguments rather than copies, and they
> do not modify their inputs, as indicated by the use of "const". You
> might just have gotten away with what you were doing, but I think it
> was bad style and potentially unsafe -- for example, someone calling
> gcd_var() with a NumericVar that came from some other computation and
> having a non-null buf would risk having the buf freed in the copy,
> leaving the original NumericVar with a buf pointing to freed memory.

Thank you for taking the time to look closely at this.  This was my
first time dealing with "numeric" so I was bound to make some mistakes.
-- 
Vik Fearing

Commits

  1. Add functions gcd() and lcm() for integer and numeric types.