Coccinelle: Add iterators/list_entry_update.cocci

list_for_each_entry uses its first argument to get from one element of
the list to the next, so it is usually not a good idea to reassign it.
The first rule finds such a reassignment and the second rule checks
that there is a path from the reassignment back to the top of the loop.
Signed-off-by: Nicolas Palix <npalix@diku.dk>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/coccinelle/iterators/list_entry_update.cocci

+/// list_for_each_entry uses its first argument to get from one element of
+/// the list to the next, so it is usually not a good idea to reassign it.
+/// The first rule finds such a reassignment and the second rule checks
+/// that there is a path from the reassignment back to the top of the loop.
+///
+// Confidence: High
+// Copyright: (C) 2010 Nicolas Palix, DIKU.  GPLv2.
+// Copyright: (C) 2010 Julia Lawall, DIKU.  GPLv2.
+// Copyright: (C) 2010 Gilles Muller, INRIA/LiP6.  GPLv2.
+// URL: http://coccinelle.lip6.fr/
+// Comments:
+// Options: -no_includes -include_headers
+
+virtual context
+virtual org
+virtual report
+
+@r@
+iterator name list_for_each_entry;
+expression x,E;
+position p1,p2;
+@@
+
+list_for_each_entry@p1(x,...) { <... x =@p2 E ...> }
+
+@depends on context && !org && !report@
+expression x,E;
+position r.p1,r.p2;
+statement S;
+@@
+
+*x =@p2 E
+...
+list_for_each_entry@p1(x,...) S
+
+// ------------------------------------------------------------------------
+
+@back depends on (org || report) && !context exists@
+expression x,E;
+position r.p1,r.p2;
+statement S;
+@@
+
+x =@p2 E
+...
+list_for_each_entry@p1(x,...) S
+
+@script:python depends on back && org@
+p1 << r.p1;
+p2 << r.p2;
+@@
+
+cocci.print_main("iterator",p1)
+cocci.print_secs("update",p2)
+
+@script:python depends on back && report@
+p1 << r.p1;
+p2 << r.p2;
+@@
+
+msg = "iterator with update on line %s" % (p2[0].line)
+coccilib.report.print_report(p1[0],msg)