Thread: Patches for static check on geo_ops.c

Grzegorz Jaskiewicz wonderful static checker coughed up 5 errors in
geo_ops.c.  None of them of any particular excitement or of earth
shattering nature. A patch is attached below that should correct these.
(The more little issue we eliminate, the more the large ones will stand
out.)

At line 3131 value stored into 'dist' variable is never referenced again.
At line 3014 value stored into 'dist' variable is never referenced again.
At line 2942 value stored into 'd' variable is never referenced again.
At line 2953 value stored into 'd' variable is never referenced again.
At line 2993 value stored into 'd' variable is never referenced again.


? patchfile_clang
Index: src/backend/utils/adt/geo_ops.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/adt/geo_ops.c,v
retrieving revision 1.103
diff -c -r1.103 geo_ops.c
*** src/backend/utils/adt/geo_ops.c    28 Jul 2009 09:47:59 -0000    1.103
--- src/backend/utils/adt/geo_ops.c    27 Aug 2009 09:31:30 -0000
***************
*** 2939,2945 ****
          memcpy(&point, &l1->p[1], sizeof(Point));
      }

!     if ((d = dist_ps_internal(&l2->p[0], l1)) < dist)
      {
          result = DatumGetPointP(DirectFunctionCall2(close_ps,
                                                      PointPGetDatum(&l2->p[0]),
--- 2939,2945 ----
          memcpy(&point, &l1->p[1], sizeof(Point));
      }

!     if (dist_ps_internal(&l2->p[0], l1) < dist)
      {
          result = DatumGetPointP(DirectFunctionCall2(close_ps,
                                                      PointPGetDatum(&l2->p[0]),
***************
*** 2950,2956 ****
                                                      LsegPGetDatum(l2)));
      }

!     if ((d = dist_ps_internal(&l2->p[1], l1)) < dist)
      {
          result = DatumGetPointP(DirectFunctionCall2(close_ps,
                                                      PointPGetDatum(&l2->p[1]),
--- 2950,2956 ----
                                                      LsegPGetDatum(l2)));
      }

!     if (dist_ps_internal(&l2->p[1], l1) < dist)
      {
          result = DatumGetPointP(DirectFunctionCall2(close_ps,
                                                      PointPGetDatum(&l2->p[1]),
***************
*** 2990,2996 ****
      point.x = box->low.x;
      point.y = box->high.y;
      statlseg_construct(&lseg, &box->low, &point);
!     dist = d = dist_ps_internal(pt, &lseg);

      statlseg_construct(&seg, &box->high, &point);
      if ((d = dist_ps_internal(pt, &seg)) < dist)
--- 2990,2996 ----
      point.x = box->low.x;
      point.y = box->high.y;
      statlseg_construct(&lseg, &box->low, &point);
!     dist = dist_ps_internal(pt, &lseg);

      statlseg_construct(&seg, &box->high, &point);
      if ((d = dist_ps_internal(pt, &seg)) < dist)
***************
*** 3011,3017 ****
      statlseg_construct(&seg, &box->high, &point);
      if ((d = dist_ps_internal(pt, &seg)) < dist)
      {
-         dist = d;
          memcpy(&lseg, &seg, sizeof(lseg));
      }

--- 3011,3016 ----
***************
*** 3128,3134 ****
      statlseg_construct(&seg, &box->high, &point);
      if ((d = lseg_dt(lseg, &seg)) < dist)
      {
-         dist = d;
          memcpy(&bseg, &seg, sizeof(bseg));
      }

--- 3127,3132 ----

On 27 Aug 2009, at 10:46, Paul Matthews wrote:

> Grzegorz Jaskiewicz wonderful static checker coughed up 5 errors in
> geo_ops.c.  None of them of any particular excitement or of earth
> shattering nature. A patch is attached below that should correct  
> these.
> (The more little issue we eliminate, the more the large ones will  
> stand
> out.)

I am flattered, but I am merely a user of it - running it against  
postgresql's source. The checker is written by wonderful llvm  
developers, so you should thank them (and apple, for sponsoring  
development of the checker).

Paul Matthews <plm@netspace.net.au> writes:
> Grzegorz Jaskiewicz wonderful static checker coughed up 5 errors in
> geo_ops.c.  None of them of any particular excitement or of earth
> shattering nature. A patch is attached below that should correct these.
> (The more little issue we eliminate, the more the large ones will stand
> out.)

> At line 3131 value stored into 'dist' variable is never referenced again.
> At line 3014 value stored into 'dist' variable is never referenced again.
> At line 2942 value stored into 'd' variable is never referenced again.
> At line 2953 value stored into 'd' variable is never referenced again.
> At line 2993 value stored into 'd' variable is never referenced again.

I've applied the first three of these changes, but not the last two
(the 'dist' assignments).  "clang" seems to have a tin ear for style :-(.
It's failing to notice that we have several similar code blocks in
sequence in these two places, and making the last one different from the
rest would decrease code readability and modifiability.  I'm happy if
the compiler optimizes away useless stores, but I don't really think
it should presume to dictate code style to us on that basis.

BTW, if we did apply those changes, I suppose clang would immediately
start complaining that the preceding assignments to 'd' are useless.
So by the time we'd made it happy, those code blocks would look quite
different from their mates.
        regards, tom lane

Tom Lane wrote:
> I've applied the first three of these changes, but not the last two
> (the 'dist' assignments).  "clang" seems to have a tin ear for style :-(.
> It's failing to notice that we have several similar code blocks in
> sequence in these two places, and making the last one different from the
> rest would decrease code readability and modifiability.
>
>   
<voice="Maxwell Smart">"Ah! The old programming via copy-and-paste
trick"</voice>.

Maybe clang's ear for style isn't that bad after all.
:-)