Support a source code search approach for finding duplicate code from two if branches

[elfring]

The analysis tool “Cppcheck 2.10.3-3.2” pointed a source code place out for further development considerations: (style) Condition 'tint==NULL' is always true [knownConditionTrueFalse]

:eyes: See also a corresponding change suggestion.

I tried another SmPL script variant out.

@replacement@
statement s;
@@
-if (tint == NULL)
-{
- ...
- cs->tint = GetColor(black);
- s
-}
+cs->tint = GetColor(tint ? tint : black);
+s

The following test result demonstrates a possible code transformation:

Markus_Elfring@Sonne:…/Projekte/fvwm3> spatch test_tint_determination2.cocci lokal/fvwm/colorset.c
…
@@ -962,14 +962,9 @@ void parse_colorset(int n, char *line)
                                have_pixels_changed = True;
                        }
                }
-               else if (tint == NULL)
-               {
-                       /* default */
-                       Pixel old_tint = cs->tint;
-                       PictureFreeColors(dpy, Pcmap, &cs->tint, 1, 0, True);
-                       cs->tint = GetColor(black);
-                       if (old_tint != cs->tint)
-                       {
+               else {
+                       cs->tint = GetColor(tint ? tint : black);
+                       if (old_tint != cs->tint) {
                                have_pixels_changed = True;
                        }
                }

:crystal_ball: How will the chances evolve to improve components of the software combination “Coccinelle 1.1.1-00478-g0afff7fa” for more desirable source code search (and change) results?

• A)

  @display1@
  declaration d;
  statement s1, s2;
  @@
  *if (tint != NULL)
  *{
  * d
  * s1
  * cs->tint = GetColor(tint);
  * s2
  *}
  *else if (tint == NULL)
  *{
  * d
  * s1
  * cs->tint = GetColor(black);
  * s2
  *}

• B)

  @display2@
  statement s1, s2;
  @@
  *if (tint != NULL)
  *{
  * ...
  * s1
  * cs->tint = GetColor(tint);
  * s2
  *}
  *else if (tint == NULL)
  *{
  * ...
  * s1
  * cs->tint = GetColor(black);
  * s2
  *}

[elfring]

How do you think about to disable isomorphisms like the following for another analysis approach (so that extra case distinctions can be avoided from the application of SmPL disjunctions)? :thinking:

• is_null
• isnt_null1
• neg_if
• ne_if
• drop_else
• commeq
• commneq
• ptr_to_array

[elfring]

Why can known source code places also not be found with the following SmPL script variant?

@display disable is_null, isnt_null1, neg_if, ne_if, drop_else, commeq, commneq, ptr_to_array@
statement s;
@@
*if (tint != NULL)
*{
* ...
* PictureFreeColors(...);
* cs->tint = GetColor(tint);
* s
*}
*else if (tint == NULL)
*{
* ...
* PictureFreeColors(...);
* cs->tint = GetColor(black);
* s
*}

:crystal_ball: How will observed difficulties be resolved for the safe application of statement metavariables?

[elfring]

• :thinking: Can any Coccinelle software component indicate which source code place could not be matched so far in the shown example?
• :crystal_ball: Will another clarification approach become helpful by the means of decision trees?