linux-kernel - Re: [PATCH V2] kconfig/menu.c: fix uninitialized variable warning

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Date:	Thu, 26 Sep 2013 19:05:20 +0200
From:	"Yann E. MORIN" <yann.morin.1998@...e.fr>
To:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Cc:	mmarek@...e.cz, bpoirier@...e.de, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] kconfig/menu.c: fix uninitialized variable warning

Madhavan, All,

On 2013-09-22 22:35 +0530, Madhavan Srinivasan spake thusly:
> In file included from scripts/kconfig/zconf.tab.c:2537:0:
> scripts/kconfig/menu.c: In function ‘get_symbol_str’:
> scripts/kconfig/menu.c:586:18: warning: ‘jump’ may be used uninitialized in
> this function [-Wmaybe-uninitialized]
>      jump->offset = r->len - 1;
>                   ^
> scripts/kconfig/menu.c:547:19: note: ‘jump’ was declared here
>   struct jump_key *jump;
>                    ^
> Change V2:
> 
> 1)Added comment as suggested.

Maybe I'm mislead, but I think Benjamin and I suggested a comment that
explained the warning was just spurious, and there would be no code
change. Something like:

    /* gcc 4.8.0 on (your distro and version) warns about 'jump may be
     * used uninitialized', which is wrong. The warning does not appear
     * with gcc != 4.8.0 */
    struct jump_key *jump;

This is so, if sometime in the future the code changes, and the variable
is indeeded used uninitialised, we have a proper warning by gcc in this
case.

Care to resend, please?

Regards,
Yann E. MORIN.

> Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
> ---
>  scripts/kconfig/menu.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
> index c1d5320..32ee2d5 100644
> --- a/scripts/kconfig/menu.c
> +++ b/scripts/kconfig/menu.c
> @@ -544,7 +544,8 @@ static void get_prompt_str(struct gstr *r, struct property *prop,
>  {
>  	int i, j;
>  	struct menu *submenu[8], *menu, *location = NULL;
> -	struct jump_key *jump;
> +	/* Initializing to avoid a spurious warning observed in gcc 4.8.0 */
> +	struct jump_key *jump = NULL;
>  
>  	str_printf(r, _("Prompt: %s\n"), _(prop->text));
>  	menu = prop->menu->parent;
> -- 
> 1.7.10.4
> 

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