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

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Date:   Mon, 29 Oct 2018 01:37:44 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Leonardo Brás <leobras.c@...il.com>
Cc:     lkcamp@...ts.libreplanetbr.org, Borislav Petkov <bp@...en8.de>,
        David.Laight@...lab.com, Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, helen@...keco.de,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] Creates macro to avoid variable shadowing

On Tue, Oct 23, 2018 at 10:11 AM Leonardo Brás <leobras.c@...il.com> 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>
> ---


Applied to linux-kbuild.



>  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;
>
>                 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;
> --
> 2.19.1
>


-- 
Best Regards
Masahiro Yamada