linux-kernel - [PATCH] coccinelle: tests: unsigned value cannot be lesser than zero

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Message-id: <1442309232-5902-1-git-send-email-a.hajda@samsung.com>
Date:	Tue, 15 Sep 2015 11:27:12 +0200
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Julia.Lawall@...6.fr
Cc:	Andrzej Hajda <a.hajda@...sung.com>, Gilles.Muller@...6.fr,
	nicolas.palix@...g.fr, mmarek@...e.com, cocci@...teme.lip6.fr,
	joe@...ches.com, linux-kernel@...r.kernel.org,
	b.zolnierkie@...sung.com
Subject: [PATCH] coccinelle: tests: unsigned value cannot be lesser than zero

Code comparing unsigned variables with zero using operators < or >= does not
make sense. It is always false or true, respectively. However, its presence
often indicates bugs in the code.
gcc can detect it also using -Wtype-limits switch, but it warns also in correct
cases, making too much noise.

Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
---
Hi Julia,

This test finds 93 issues in kernel code (with --all-includes) which could
be corrected. Some of them are harmless, just unnecessary code, but there
are also serious bugs, like:
	u32 irq = platform_get_irq(...)
	if (irq < 0)
		...
	unsigned int target = cpumask_any_but(cpu_online_mask, cpu);
	if (target < 0)
		...

Regards
Andrzej
---
 .../tests/unsigned_lesser_than_zero.cocci          | 37 ++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci

diff --git a/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci b/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci
new file mode 100644
index 0000000..6a90510
--- /dev/null
+++ b/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci
@@ -0,0 +1,37 @@
+/// Unsigned variables cannot be lesser than zero. Presence of such checks
+/// can indicate incorrect variable type or just unnecessary code.
+///
+// Confidence: High
+// Copyright: (C) 2015 Andrzej Hajda, Samsung Electronics Co., Ltd. GPLv2.
+// URL: http://coccinelle.lip6.fr/
+// Options: --include-headers
+
+virtual context
+virtual org
+virtual report
+
+@r depends on context || org || report@
+position p;
+typedef u8, u16, u32, u64;
+{unsigned char, unsigned short int, unsigned int, unsigned long, unsigned long long, size_t, u8, u16, u32, u64} v;
+@@
+
+(
+*v@p < 0
+|
+*v@p >= 0
+)
+
+@...ipt:python depends on org@
+p << r.p;
+@@
+
+msg = "WARNING: Unsigned value cannot be lesser than zero"
+coccilib.org.print_todo(p[0], msg)
+
+@...ipt:python depends on report@
+p << r.p;
+@@
+
+msg = "WARNING: Unsigned value cannot be lesser than zero"
+coccilib.report.print_report(p[0], msg)
-- 
1.9.1

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