linux-kernel - Re: [PATCH 07/11] mfd: Drop unnecessary static

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Date:   Sat, 15 Jul 2017 13:49:26 -0700
From:   Mark D Rustad <mrustad@...il.com>
To:     Julia Lawall <Julia.Lawall@...6.fr>
Cc:     Tony Lindgren <tony@...mide.com>, keescook@...omium.org,
        kernel-janitors@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/11] mfd: Drop unnecessary static

> On Jul 15, 2017, at 1:07 PM, Julia Lawall <Julia.Lawall@...6.fr> wrote:
> 
> Drop static on a local variable, when the variable is initialized before
> any possible use.  Thus, the static has no benefit.

I think in this case the use relies on the structure continuing to exist, so a stack object is not an acceptable substitute. Just because it is initialized doesn't mean that it doesn't need a persistent lifetime.

> The semantic patch that fixes this problem is as follows:
> (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @bad exists@
> position p;
> identifier x;
> type T;
> @@
> static T x@p;
> ...
> x = <+...x...+>
> 
> @@
> identifier x;
> expression e;
> type T;
> position p != bad.p;
> @@
> -static
> T x@p;
> ... when != x
>     when strict
> ?x = e;
> // </smpl>
> 
> Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
> 
> ---
> These patches are all independent of each other.
> 
> drivers/mfd/twl4030-irq.c |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff -u -p a/drivers/mfd/twl4030-irq.c b/drivers/mfd/twl4030-irq.c
> --- a/drivers/mfd/twl4030-irq.c
> +++ b/drivers/mfd/twl4030-irq.c
> @@ -685,7 +685,7 @@ int twl4030_sih_setup(struct device *dev
> 
> int twl4030_init_irq(struct device *dev, int irq_num)
> {
> -	static struct irq_chip	twl4030_irq_chip;
> +	struct irq_chip		twl4030_irq_chip;
> 	int			status, i;
> 	int			irq_base, irq_end, nr_irqs;
> 	struct			device_node *node = dev->of_node;

--
Mark Rustad, MRustad@...il.com


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