coccinelle: misc: add swap script

Check for opencoded swap() implementation.
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>

scripts/coccinelle/misc/swap.cocci

+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Check for opencoded swap() implementation.
+///
+// Confidence: High
+// Copyright: (C) 2021 Denis Efremov ISPRAS
+// Options: --no-includes --include-headers
+//
+// Keywords: swap
+//
+
+virtual patch
+virtual org
+virtual report
+virtual context
+
+@rvar depends on !patch@
+identifier tmp;
+expression a, b;
+type T;
+position p;
+@@
+
+(
+* T tmp;
+|
+* T tmp = 0;
+|
+* T *tmp = NULL;
+)
+... when != tmp
+* tmp = a;
+* a = b;@p
+* b = tmp;
+... when != tmp
+
+@r depends on !patch@
+identifier tmp;
+expression a, b;
+position p != rvar.p;
+@@
+
+* tmp = a;
+* a = b;@p
+* b = tmp;
+
+@rpvar depends on patch@
+identifier tmp;
+expression a, b;
+type T;
+@@
+
+(
+- T tmp;
+|
+- T tmp = 0;
+|
+- T *tmp = NULL;
+)
+... when != tmp
+- tmp = a;
+- a = b;
+- b = tmp
++ swap(a, b)
+  ;
+... when != tmp
+
+@rp depends on patch@
+identifier tmp;
+expression a, b;
+@@
+
+- tmp = a;
+- a = b;
+- b = tmp
++ swap(a, b)
+  ;
+
+@depends on patch && (rpvar || rp)@
+@@
+
+(
+  for (...;...;...)
+- {
+	swap(...);
+- }
+|
+  while (...)
+- {
+	swap(...);
+- }
+|
+  if (...)
+- {
+	swap(...);
+- }
+)
+
+
+@script:python depends on report@
+p << r.p;
+@@
+
+coccilib.report.print_report(p[0], "WARNING opportunity for swap()")
+
+@script:python depends on org@
+p << r.p;
+@@
+
+coccilib.org.print_todo(p[0], "WARNING opportunity for swap()")
+
+@script:python depends on report@
+p << rvar.p;
+@@
+
+coccilib.report.print_report(p[0], "WARNING opportunity for swap()")
+
+@script:python depends on org@
+p << rvar.p;
+@@
+
+coccilib.org.print_todo(p[0], "WARNING opportunity for swap()")