linux-kernel - Re: [coccicheck PATCH 4/5] Deletion of unnecessary checks before specific function calls

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Date:	Wed, 01 Oct 2014 16:07:12 +0200
From:	SF Markus Elfring <elfring@...rs.sourceforge.net>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>
CC:	Coccinelle <cocci@...teme.lip6.fr>,
	kernel-janitors@...r.kernel.org, Michal Marek <mmarek@...e.cz>,
	Chi Pham <chidaph@...il.com>,
	Fabian Frederick <fabf@...net.be>,
	Joe Perches <joe@...ches.com>
Subject: Re: [coccicheck PATCH 4/5] Deletion of unnecessary checks before
 specific function calls

>>> If you are convinced that dropping the null tests is a good idea, then you 
>>> can submit the patch that makes the change to the relevant maintainers and 
>>> mailing lists.

>From e6a21b920fcca2f6f01c9528909dc036a9b3bc41 Mon Sep 17 00:00:00 2001
From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Wed, 5 Mar 2014 19:10:32 +0100
Subject: [PATCH 4/5] Addition of a semantic patch file for listing of
 unnecessary checks before a few known functions

This semantic patch pattern tries to find source code places where a check
is performed for an expression that is passed to a function (like "kfree")
which checks this single parameter itself for usability.
Redundant value or pointer checks can be avoided here.

The pattern contains a special comment in a regular expression for a SmPL
constraint which supports extensions.

It uses Python statements to write information about the found places in
a data format that is a variant of a CSV text file.

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 ...nctions_with_unnecessary_checks_template1.cocci | 59 ++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644
scripts/coccinelle/deletions/list_functions_with_unnecessary_checks_template1.cocci

diff --git
a/scripts/coccinelle/deletions/list_functions_with_unnecessary_checks_template1.cocci
b/scripts/coccinelle/deletions/list_functions_with_unnecessary_checks_template1.cocci
new file mode 100644
index 0000000..d2637e8
--- /dev/null
+++
b/scripts/coccinelle/deletions/list_functions_with_unnecessary_checks_template1.cocci
@@ -0,0 +1,59 @@
+@...tialize:python@
+@@
+import sys
+result = []
+mark = ['"', '', '"']
+delimiter = '|'
+
+def store_positions(fun, point, places):
+    """Add source code positions to an internal list."""
+    for place in places:
+        fields = []
+        fields.append(fun)
+
+        fields.append(point)
+
+        mark[1] = place.file.replace('"', '""')
+        fields.append(''.join(mark))
+
+        fields.append(place.line)
+        fields.append(str(int(place.column) + 1))
+        result.append(delimiter.join(fields))
+
+@...unnecessary_check@
+expression data;
+identifier work;
+identifier release =~ "^(?x)
+(?:
+   (?:kz?|slob_)free
+|
+   (?:
+# Alternation placeholder
+   )
+)$";
+position pos;
+type t;
+@@
+ t work@pos(...)
+ {
+  ... when any
+( if (data) release(data);
+| if (likely(data)) release(data);
+)
+  ... when any
+ }
+
+@...ipt:python collection depends on is_unnecessary_check@
+fun << is_unnecessary_check.work;
+point << is_unnecessary_check.data;
+places << is_unnecessary_check.pos;
+@@
+store_positions(fun, point, places)
+
+@...alize:python@
+@@
+if result:
+   result.insert(0, delimiter.join(("function", '"parameter"', '"source file"',
"line", "column")))
+   print("\r\n".join(result))
+else:
+   sys.stderr.write("No result for this analysis!\n")
-- 
1.9.0



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