linux-kernel - Re: [PATCH 3/7] lib/random32.c: Replace an #ifdef with a stub prandom_state

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Message-ID: <20140608122713.1627.qmail@ns.horizon.com>
Date:	8 Jun 2014 08:27:13 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	dborkman@...hat.com, linux@...izon.com
Cc:	davem@...emloft.net, hannes@...essinduktion.org,
	linux-kernel@...r.kernel.org, shemminger@...l.org, tytso@....edu
Subject: Re: [PATCH 3/7] lib/random32.c: Replace an #ifdef with a stub prandom_state_selftest()

>>   #ifdef CONFIG_RANDOM32_SELFTEST
>>   static void __init prandom_state_selftest(void);
>> +#else
>> +#define prandom_state_selftest() (void)0

> Fine by me. I think you can remove this '(void)0' here, though.

That's the standard way to write a no-op statement in C.

I seem to recall there's a reason that the empty string can cause problems
in some syntactic contexts, but I can't figure out what the situation is.

At first, I thought of the obvious:

if (condition)
	prandom_state_selftest();
unconditional_code();

... but the semicolon makes that work.  I'll try to remember
the reason.

(I know that nobody uses it in any such context, but it's
good manners to make a function-like macro behave as exactly
like a function as possible.)
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