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

[Christoph Berg]

Re: Andres Freund 2017-12-13 <20171213173524.rjs7b3ahsong5...@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 <m...@debian.org> wrote:
> > > Re: Andres Freund 2017-12-13 <e1eovqf-00075r...@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

diff --git a/src/include/common/int.h b/src/include/common/int.h
new file mode 100644
index e44d42f..e6907c6
*** a/src/include/common/int.h
--- b/src/include/common/int.h
*************** pg_add_s16_overflow(int16 a, int16 b, in
*** 41,47 ****
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 41,47 ----
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a - b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
*************** pg_sub_s16_overflow(int16 a, int16 b, in
*** 61,67 ****
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 61,67 ----
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a * b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
*************** pg_add_s32_overflow(int32 a, int32 b, in
*** 101,107 ****
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 101,107 ----
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a - b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
*************** pg_sub_s32_overflow(int32 a, int32 b, in
*** 121,127 ****
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 121,127 ----
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a * b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
*************** pg_add_s64_overflow(int64 a, int64 b, in
*** 167,173 ****
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 167,173 ----
  }
  
  /*
!  * If a - b overflows, return true, otherwise store the result of a - b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
*************** pg_sub_s64_overflow(int64 a, int64 b, in
*** 193,199 ****
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a + b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */
--- 193,199 ----
  }
  
  /*
!  * If a * b overflows, return true, otherwise store the result of a * b into
   * *result. The content of *result is implementation defined in case of
   * overflow.
   */