linux-kernel - Re: [PATCH] rcu: remove unused variable in boot_cpu_state

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Message-ID: <20170622075410.pur2m5dobqcwosjh@gmail.com>
Date:   Thu, 22 Jun 2017 09:54:10 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Arnd Bergmann <arnd@...db.de> wrote:
> 
> > > So I think we should consider it a syntactic construct to avoid.
> > 
> > Unused variables are relatively harmless compared to used-uninitialized
> > variables that are always bugs (though they are provably impossible to
> > detect correctly in some cases).
> 
> So the thing I was most worried about was that old GCC used to not warn about:
> 
> 	long __maybe_unused error;
> 
> 	...
> 
> 	if (error)
> 		return error;

Gah - I got totally confused, the dangerous construct I was thinking of was 
uninitialized_var(), not __maybe_unused.

So ignore my replies! :-)

Thanks,

	Ingo