linux-kernel - RE: linux-4.1-rc7/drivers/irqchip/irq-renesas-intc-irqpin.c:418: array index used before limits check ?

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Message-ID: <alpine.DEB.2.11.1506081523510.4133@nanos>
Date:	Mon, 8 Jun 2015 15:26:12 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Binderman <dcb314@...mail.com>
cc:	"jason@...edaemon.net" <jason@...edaemon.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: linux-4.1-rc7/drivers/irqchip/irq-renesas-intc-irqpin.c:418:
 array index used before limits check ?

On Mon, 8 Jun 2015, David Binderman wrote:
> ----------------------------------------
> >> [linux-4.1-rc7/drivers/irqchip/irq-renesas-intc-irqpin.c:418]: (style) Array ind
> >> ex 'k' is used before limits check.
> >>
> >>    if (!io[k] && k < INTC_IRQPIN_REG_NR_MANDATORY) {
> >>
> >> Suggest sanity check array index before use.
> >
> > Which version of gcc is being stupid here?
> 
> None of them. 
> 
> The original "(style)" message is from a static analysis tool called cppcheck.
> 
> I can't think of a situation where, if an array index needs checking, then
> it should be checked *after* use.

It does not check the array index. Read the complete code:

        for (k = 0; k < INTC_IRQPIN_REG_NR; k++) {
                io[k] = platform_get_resource(pdev, IORESOURCE_MEM, k);
                if (!io[k] && k < INTC_IRQPIN_REG_NR_MANDATORY) {

The array bound is INTC_IRQPIN_REG_NR and the check about which that
tool complains has nothing to do with array bounds. Completely valid
code.

Thanks,

	tglx




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