linux-kernel - Re: [patch] x86, ptrace: void dopiness

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Date:	Fri, 19 Sep 2008 09:17:11 -0400
From:	"linux-os (Dick Johnson)" <linux-os@...logic.com>
To:	"Markus Metzger" <markus.t.metzger@...el.com>
Cc:	<mingo@...e.hu>, <markus.t.metzger@...il.com>,
	<linux-kernel@...r.kernel.org>, <akpm@...ux-foundation.org>
Subject: Re: [patch] x86, ptrace: void dopiness

On Fri, 19 Sep 2008, Markus Metzger wrote:

> Remove void cast to explicitly ignore the return value.
>
>
> Signed-off-by: markus.t.metzger@...el.com
>
> ---
> Index: gits.x86/arch/x86/kernel/ptrace.c
> ===================================================================
> --- gits.x86.orig/arch/x86/kernel/ptrace.c	2008-06-30 13:21:07.%N +0200
> +++ gits.x86/arch/x86/kernel/ptrace.c	2008-09-19 13:53:02.%N +0200
> @@ -738,7 +738,7 @@
> 		unsigned int sig = 0;
>
> 		/* we ignore the error in case we were not tracing child */
> -		(void)ds_release_bts(child);
> +		ds_release_bts(child);
>
> 		if (cfg.flags & PTRACE_BTS_O_SIGNAL) {
> 			if (!cfg.signal)
> @@ -947,7 +947,7 @@
> 	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
> #endif
> #ifdef CONFIG_X86_PTRACE_BTS
> -	(void)ds_release_bts(child);
> +	ds_release_bts(child);
>
> 	child->thread.debugctlmsr &= ~bts_cfg.debugctl_mask;
> 	if (!child->thread.debugctlmsr)
> ---------------------------------------------------------------------
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I don't agree. Casting the return value to void, since it
takes extra steps on the part of the writer, means that the
writer is deliberately ignoring the return value because
it has no objective use in the code.

Just letting unused return-values be ignored means that
the writer either wanted to ignore it or simply forgot
about it. The cast is supposed to remove doubt. Certain
user-mode functions that are obviously used for effect
like printf(), are exempt.

That said, putting a space between the cast and the
function name helps in the use of some text-scanning
tools and therefore improves maintainability.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.25.17 on an i686 machine (4786.70 BogoMips).
My book : http://www.AbominableFirebug.com/
_

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