coccinelle: Add script to find cases of unsigned < 0

Unsigned expressions cannot be less than zero and presence
of such practices very likely indicates a bug.

Signed-off-by: Himanshu Jha <[email protected]>

Author: himanshujha199640

scripts/coccinelle/unsigned_lesser_than_zero.cocci

@@ -0,0 +1,33 @@
+/// Unsigned expressions cannot be lesser than zero. Presence of
+/// comparisons 'unsigned (<|<=) 0' often indicates a bug,
+/// usually wrong type of variable.
+///
+// Confidence: High
+// Copyright: (C) 2015 Andrzej Hajda, Samsung Electronics Co., Ltd. GPLv2.
+// URL: http://coccinelle.lip6.fr/
+
+virtual org
+virtual report
+
+@r_cmp depends on !(file in "ext")@
+position p;
+typedef u8_t, u16_t, u32_t, u64_t;
+{unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long,
+	size_t, u8_t, u16_t, u32_t, u64_t} v;
+@@
+
+	(\( v@p < 0 \| v@p <= 0 \))
+
+@script:python depends on org@
+p << r_cmp.p;
+@@
+
+msg = "WARNING: Unsigned expression compared with zero."
+coccilib.org.print_todo(p[0], msg)
+
+@script:python depends on report@
+p << r_cmp.p;
+@@
+
+msg = "WARNING: Unsigned expression compared with zero."
+coccilib.report.print_report(p[0], msg)