linux-kernel - Re: [Nouveau] [PATCH] nouveau: hide gcc-4.9 -Wmaybe-uninitialized

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Date:   Mon, 24 Oct 2016 17:51:01 +0200
From:   Karol Herbst <karolherbst@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        ML nouveau <nouveau@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [Nouveau] [PATCH] nouveau: hide gcc-4.9 -Wmaybe-uninitialized

uhh, that function looks so odd, ... yeah. Change looks fine.

Reviewed-By: Karol Herbst <karolherbst@...il.com>

2016-10-24 17:30 GMT+02:00 Arnd Bergmann <arnd@...db.de>:
> gcc-4.9 notices that the validate_init() function returns unintialized
> data when called with a zero 'nr_buffers' argument, when called with the
> -Wmaybe-uninitialized flag:
>
> drivers/gpu/drm/nouveau/nouveau_gem.c: In function ‘validate_init.isra.6’:
> drivers/gpu/drm/nouveau/nouveau_gem.c:457:5: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> However, the only caller of this function always passes a nonzero
> argument, and gcc-6 is clever enough to take this into account and
> not warn about it any more.
>
> Adding an explicit initialization to -EINVAL here is correct even if
> the caller changed, and it avoids the warning on gcc-4.9 as well.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/gpu/drm/nouveau/nouveau_gem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index 0bd7164bc817..4f3c5f3eaa16 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -369,7 +369,7 @@ validate_init(struct nouveau_channel *chan, struct drm_file *file_priv,
>  {
>         struct nouveau_cli *cli = nouveau_cli(file_priv);
>         int trycnt = 0;
> -       int ret, i;
> +       int ret = -EINVAL, i;
>         struct nouveau_bo *res_bo = NULL;
>         LIST_HEAD(gart_list);
>         LIST_HEAD(vram_list);
> --
> 2.9.0
>
> _______________________________________________
> Nouveau mailing list
> Nouveau@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/nouveau

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