From f2027543b9cb47e1853d8c34fe931e2fcee5cb65 Mon Sep 17 00:00:00 2001
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date: Thu, 16 Apr 2015 12:43:31 -0700
Subject: documentation: update CodingStyle on local variables naming in macros

Describe proper naming convention for local variables in macros
resembling functions.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 Documentation/CodingStyle | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'Documentation/CodingStyle')

diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 449a8a19fc21..4d4f06d47e06 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -659,6 +659,19 @@ macros using parameters.
 #define CONSTANT 0x4000
 #define CONSTEXP (CONSTANT | 3)
 
+5) namespace collisions when defining local variables in macros resembling
+functions:
+
+#define FOO(x)				\
+({					\
+	typeof(x) ret;			\
+	ret = calc_ret(x);		\
+	(ret);				\
+)}
+
+ret is a common name for a local variable - __foo_ret is less likely
+to collide with an existing variable.
+
 The cpp manual deals with macros exhaustively. The gcc internals manual also
 covers RTL which is used frequently with assembly language in the kernel.
 
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