linux-kernel - [PATCH] Coccinelle: doubletest: reduce side effect false positives

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Date:   Fri,  3 Aug 2018 18:32:11 +0200
From:   Julia Lawall <Julia.Lawall@...6.fr>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     kernel-janitors@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>, cocci@...teme.lip6.fr,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Finn Thain <fthain@...egraphics.com.au>,
        zhong jiang <zhongjiang@...wei.com>,
        Michael Schmitz <schmitzmic@...il.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        John Garry <john.garry@...wei.com>,
        linux-scsi <linux-scsi@...r.kernel.org>
Subject: [PATCH] Coccinelle: doubletest: reduce side effect false positives

Ensure that the cited expression is not a function call or an
assignment to reduce the chance of false positives.

Slightly modify the warning message to indicate another source
of false positves.

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 scripts/coccinelle/tests/doubletest.cocci |   34 ++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/scripts/coccinelle/tests/doubletest.cocci b/scripts/coccinelle/tests/doubletest.cocci
index 78d74c2..7af2ce7 100644
--- a/scripts/coccinelle/tests/doubletest.cocci
+++ b/scripts/coccinelle/tests/doubletest.cocci
@@ -1,6 +1,7 @@
 /// Find &&/|| operations that include the same argument more than once
-//# A common source of false positives is when the argument performs a side
-//# effect.
+//# A common source of false positives is when the expression, or
+//# another expresssion in the same && or || operation, performs a
+//# side effect.
 ///
 // Confidence: Moderate
 // Copyright: (C) 2010 Nicolas Palix, DIKU.  GPLv2.
@@ -20,20 +21,37 @@ position p;
 @@
 
 (
-* E@p
-  || ... || E
+ E@p || ... || E
 |
-* E@p
-  && ... && E
+ E@p && ... && E
 )
 
-@...ipt:python depends on org@
+@bad@
+expression r.E,e1,e2,fn;
+position r.p;
+assignment operator op;
+@@
+
+(
+E@p
+&
+ <+... \(fn(...)\|e1 op e2\|e1++\|e1--\|++e1\|--e1\) ...+>
+)
+
+@...ends on context && !bad@
+expression r.E;
+position r.p;
+@@
+
+*E@p
+
+@...ipt:python depends on org && !bad@
 p << r.p;
 @@
 
 cocci.print_main("duplicated argument to && or ||",p)
 
-@...ipt:python depends on report@
+@...ipt:python depends on report && !bad@
 p << r.p;
 @@