Horton

Re: pgsql: Provide overflow safe integer math inline functions.

Christoph Berg <myon@debian.org>

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From: Christoph Berg <myon@debian.org>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-committers <pgsql-hackers@postgresql.org>
Date: 2017-12-14T08:28:08Z
Lists: pgsql-hackers

Attachments

Re: Andres Freund 2017-12-13 <20171213173524.rjs7b3ahsong5zko@alap3.anarazel.de>
> On 2017-12-13 09:37:25 -0500, Robert Haas wrote:
> > On Wed, Dec 13, 2017 at 5:10 AM, Christoph Berg <myon@debian.org> wrote:
> > > Re: Andres Freund 2017-12-13 <E1eOvQF-00075r-Cy@gemulon.postgresql.org>
> > >> Provide overflow safe integer math inline functions.
> > >
> > > The new _overflow functions have buggy comments:
> > >
> > > /*
> > >  * If a - b overflows, return true, otherwise store the result of a + b into
> > >  * *result.                                                         ^ there
> > 
> > What's wrong with that?
> 
> After staring at it for a while, I seem to have partially mis-copied the
> note for addition to the subtraction operation...

I believe the attached is the correct version.

Christoph

Commits

  1. Try harder to detect unavailability of __builtin_mul_overflow(int64).

  2. Try to detect runtime unavailability of __builtin_mul_overflow(int64).

  3. Fix a number of copy & paste comment errors in common/int.h.

  4. Provide overflow safe integer math inline functions.