linux-kernel - checkpatch.pl: Wrong check SINGLE_STATEMENT_DO_WHILE

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Message-ID: <4204029.7cYAuJfu4T@bentobox>
Date:	Thu, 02 Aug 2012 10:00:04 +0200
From:	Schrober <franzschrober@...oo.de>
To:	Joe Perches <joe@...ches.com>
Cc:	Andy Whitcroft <apw@...onical.com>, linux-kernel@...r.kernel.org
Subject: checkpatch.pl: Wrong check SINGLE_STATEMENT_DO_WHILE_MACRO

Hi,

I think your check for SINGLE_STATEMENT_DO_WHILE_MACRO is wrong. Just to give 
an example:

#define foobar(x) \
	do { \
		if (pizza_ready(x)) \
			eat_pizza(x); \
	} while (0)

if (hungry(y))
	foobar(x);
else
	barfoo(x);

checkpatch does now complain about something like "WARNING: Single statement 
macros should not use a do {} while (0) loop"

But we would have an ambiguous else when the do-while is removed. The code 
works as expected with the do-while but the else is "attached" to the wrong 
"if" when the do-while is removed.

And yes, this example is made that easy to make it easy to understand. There 
are examples were static inline code would not work very well (vararg for 
example).

Please fix or remove your check. Otherwise some people will be start to 
overeagerly change these macros and break the kernel doing that.
-- 
Franz Schrober
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