[Cocci] false positive match with ternary operator?

[julia.lawall@lip6.fr (Julia Lawall)]

On Wed, 17 Feb 2016, Wolfram Sang wrote:

> So, I'll try again ;) This spatch:
>
> @@
> identifier match;
> expression table, dev;
> type T;
> @@
> -	T match = of_match_device(table, dev);
> 	... when != match
> -	match->data
> +	of_device_get_match_data(dev)
> 	... when != match
>
> gives a match for:
>
> $ spatch -sp_file /tmp/minimal.cocci drivers/usb/renesas_usbhs/common.c
> ...
> --- drivers/usb/renesas_usbhs/common.c
> +++ /tmp/cocci-output-18078-7b0a6b-common.c
> @@ -498,7 +498,6 @@ static struct renesas_usbhs_platform_inf
>  {
>  	struct renesas_usbhs_platform_info *info;
>  	struct renesas_usbhs_driver_param *dparam;
> -	const struct of_device_id *of_id = of_match_device(usbhs_of_match, dev);
>  	u32 tmp;
>  	int gpio;
>
> @@ -507,7 +506,7 @@ static struct renesas_usbhs_platform_inf
>  		return NULL;
>
>  	dparam = &info->driver_param;
> -	dparam->type = of_id ? (uintptr_t)of_id->data : 0;
> +	dparam->type = of_id ? (uintptr_t)of_device_get_match_data(dev) : 0;
>  	if (!of_property_read_u32(dev->of_node, "renesas,buswait", &tmp))
>  		dparam->buswait_bwait = tmp;
>  	gpio = of_get_named_gpio_flags(dev->of_node, "renesas,enable-gpio", 0,
>
> However, 'of_id' is used as the first argument of the ternary operator. So,
> shouldn't '... when != match' prevent this, since 'match' is used before the
> replacement?

No, Coccinelle doesn't know anything about the order or execution within
expressions, neither ?: nor && and ||

Maybe make a big disjunction around the pattern, and make two cases
starting from the point of T match = of_match_device(table, dev);

julia