linux-kernel - Re: [PATCH v2 3/5] Creates macro to avoid variable shadowing

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Date:   Tue, 23 Oct 2018 18:35:49 -0300
From:   Helen Koike <helen@...keco.de>
To:     Leonardo Brás <leobras.c@...il.com>,
        lkcamp@...ts.libreplanetbr.org
Cc:     Borislav Petkov <bp@...en8.de>, David.Laight@...lab.com,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] Creates macro to avoid variable shadowing

Hi Leonardo,

On 10/22/18 11:10 PM, Leonardo Brás wrote:
> Creates DEF_FIELD_ADDR_VAR as a more generic version of the DEF_FIELD_ADD
> macro, allowing usage of a variable name other than the struct element name.
> Also, sets DEF_FIELD_ADDR as a specific usage of DEF_FILD_ADDR_VAR in which
> the var name is the same as the struct element name.
> 
> Signed-off-by: Leonardo Brás <leobras.c@...il.com>
> ---
>  scripts/mod/file2alias.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index 7be43697ff84..3015c0bdecb2 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -95,12 +95,20 @@ extern struct devtable *__start___devtable[], *__stop___devtable[];
>   */
>  #define DEF_FIELD(m, devid, f) \
>  	typeof(((struct devid *)0)->f) f = TO_NATIVE(*(typeof(f) *)((m) + OFF_##devid##_##f))
> +
> +/* Define a variable v that holds the address of field f of struct devid
> + * based at address m.  Due to the way typeof works, for a field of type
> + * T[N] the variable has type T(*)[N], _not_ T*.
> + */
> +#define DEF_FIELD_ADDR_VAR(m, devid, f, v) \
> +	typeof(((struct devid *)0)->f) *v = ((m) + OFF_##devid##_##f)
> +
>  /* Define a variable f that holds the address of field f of struct devid
>   * based at address m.  Due to the way typeof works, for a field of type
>   * T[N] the variable has type T(*)[N], _not_ T*.
>   */
>  #define DEF_FIELD_ADDR(m, devid, f) \
> -	typeof(((struct devid *)0)->f) *f = ((m) + OFF_##devid##_##f)
> +	DEF_FIELD_ADDR_VAR(m, devid, f, f)
>  
>  /* Add a table entry.  We test function type matches while we're here. */
>  #define ADD_TO_DEVTABLE(device_id, type, function) \
> @@ -641,25 +649,27 @@ static void do_pnp_card_entries(void *symval, unsigned long size,
>  	unsigned int i;
>  
>  	device_id_check(mod->name, "pnp", size, id_size, symval);
> +	DEF_FIELD_ADDR(symval, pnp_card_device_id, devs);
> +	typeof(devs) devs_last;
>  
>  	for (i = 0; i < count; i++) {
>  		unsigned int j;
> -		DEF_FIELD_ADDR(symval + i*id_size, pnp_card_device_id, devs);
> +		devs_last = devs + i * id_size;

Instead of doing all these changes, you could just modify here with
		DEF_FIELD_ADDR_VAR(symval + i*id_size, pnp_card_device_id, devs,
devs_aux);

Like this you are not changing the logic in this file, you are just
renaming the variable which is more then enough to solve the -Wshadow
warning.
I don't it is worthy changing the logic.

Regards,
Helen.

>  
>  		for (j = 0; j < PNP_MAX_DEVICES; j++) {
> -			const char *id = (char *)(*devs)[j].id;
> -			int i2, j2;
> +			const char *id = (char *)(*devs_last)[j].id;
> +			int j2;
>  			int dup = 0;
>  
>  			if (!id[0])
>  				break;
>  
>  			/* find duplicate, already added value */
> -			for (i2 = 0; i2 < i && !dup; i2++) {
> -				DEF_FIELD_ADDR(symval + i2*id_size, pnp_card_device_id, devs);
> +			while ((devs_last -= id_size) >= devs && !dup) {
>  
>  				for (j2 = 0; j2 < PNP_MAX_DEVICES; j2++) {
> -					const char *id2 = (char *)(*devs)[j2].id;
> +					const char *id2 =
> +						(char *)(*devs_last)[j2].id;
>  
>  					if (!id2[0])
>  						break;
>