linux-kernel - Re: [PATCH v7 02/10] staging: fsl-mc: fix macros with possible side effects

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Message-ID: <20170613101225.GA27165@kroah.com>
Date:   Tue, 13 Jun 2017 12:12:25 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     laurentiu.tudor@....com
Cc:     stuyoder@...il.com, devel@...verdev.osuosl.org, arnd@...db.de,
        marc.zyngier@....com, roy.pledge@....com,
        linux-kernel@...r.kernel.org, agraf@...e.de,
        catalin.horghidan@....com, ioana.ciornei@....com,
        leoyang.li@....com, bharat.bhushan@....com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7 02/10] staging: fsl-mc: fix macros with possible side
 effects

On Thu, Jun 08, 2017 at 05:28:47PM +0300, laurentiu.tudor@....com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> Several macros were triggering this checkpatch.pl warning:
>   "Macro argument reuse '$arg' - possible side-effects?"
> Fix the warning by avoiding multiple macro argument use.
> 
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
> ---
> 
> Notes:
>     -v7
>       -no changes
> 
>  drivers/staging/fsl-mc/bus/dprc-driver.c      | 10 +++++++---
>  drivers/staging/fsl-mc/bus/fsl-mc-allocator.c | 11 +++++++----
>  2 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/fsl-mc/bus/dprc-driver.c b/drivers/staging/fsl-mc/bus/dprc-driver.c
> index d723c69..39c9a3b 100644
> --- a/drivers/staging/fsl-mc/bus/dprc-driver.c
> +++ b/drivers/staging/fsl-mc/bus/dprc-driver.c
> @@ -21,9 +21,13 @@
>  
>  #define FSL_MC_DPRC_DRIVER_NAME    "fsl_mc_dprc"
>  
> -#define FSL_MC_DEVICE_MATCH(_mc_dev, _obj_desc) \
> -	(strcmp((_mc_dev)->obj_desc.type, (_obj_desc)->type) == 0 && \
> -	 (_mc_dev)->obj_desc.id == (_obj_desc)->id)
> +#define FSL_MC_DEVICE_MATCH(_mc_dev, _obj_desc)				\
> +({									\
> +	struct fsl_mc_device *__mc_dev = _mc_dev;			\
> +	struct dprc_obj_desc *__obj_desc = _obj_desc;			\
> +	(strcmp(__mc_dev->obj_desc.type, __obj_desc->type) == 0 &&	\
> +	__mc_dev->obj_desc.id == __obj_desc->id);			\
> +})

Ick, no.  Just make this a real function please.

>  
>  struct dprc_child_objs {
>  	int child_count;
> diff --git a/drivers/staging/fsl-mc/bus/fsl-mc-allocator.c b/drivers/staging/fsl-mc/bus/fsl-mc-allocator.c
> index ce07096..d3def40 100644
> --- a/drivers/staging/fsl-mc/bus/fsl-mc-allocator.c
> +++ b/drivers/staging/fsl-mc/bus/fsl-mc-allocator.c
> @@ -17,10 +17,13 @@
>  #include "dpcon-cmd.h"
>  #include "fsl-mc-private.h"
>  
> -#define FSL_MC_IS_ALLOCATABLE(_obj_type) \
> -	(strcmp(_obj_type, "dpbp") == 0 || \
> -	 strcmp(_obj_type, "dpmcp") == 0 || \
> -	 strcmp(_obj_type, "dpcon") == 0)
> +#define FSL_MC_IS_ALLOCATABLE(_obj_type)	\
> +({						\
> +	const char *__obj_type = _obj_type;	\
> +	(strcmp(__obj_type, "dpbp") == 0 ||	\
> +	 strcmp(__obj_type, "dpmcp") == 0 ||	\
> +	 strcmp(__obj_type, "dpcon") == 0);	\
> +})

Same here.  Don't put real logic in a #define, it never makes sense to
do it and only makes things much harder to debug.

thanks,

greg k-h