linux-kernel - Re: [PATCH] kbuild: Add option to turn incompatible pointer check into error

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Message-ID: <alpine.DEB.2.11.1603081010000.6083@nanos>
Date:	Tue, 8 Mar 2016 10:10:21 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Daniel Wagner <wagi@...om.org>
cc:	Michal Marek <mmarek@...e.com>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Daniel Wagner <daniel.wagner@...-carit.de>
Subject: Re: [PATCH] kbuild: Add option to turn incompatible pointer check
 into error

On Tue, 8 Mar 2016, Daniel Wagner wrote:

> From: Daniel Wagner <daniel.wagner@...-carit.de>
> 
> With the introduction of the simple wait API we have two very
> similar APIs in the kernel. For example wake_up() and swake_up()
> is only one character away. Although the compiler will warn
> happily the wrong usage it keeps on going an even links the kernel.
> Thomas and Peter would rather like to see early missuses reported
> as error early on.
> 
> In a first attempt we tried to wrap all swait and wait calls
> into a macro which has an compile time type assertion. The result
> was pretty ugly and wasn't able to catch all wrong usages.
> woken_wake_function(), autoremove_wake_function() and wake_bit_function()
> are assigned as function pointers. Wrapping them with a macro around is
> not possible. Prefixing them with '_' was also not a real option
> because there some users in the kernel which do use them as well.
> All in all this attempt looked to intrusive and too ugly.
> 
> An alternative is to turn the pointer type check into an error which
> catches wrong type uses. Obviously not only the swait/wait ones. That
> isn't a bad thing either.
> 
> Signed-off-by: Daniel Wagner <daniel.wagner@...-carit.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Thomas Gleixner <tglx@...utronix.de>