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>
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 449a8a1..4d4f06d 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -659,6 +659,19 @@
#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.