linux-kernel - Re: [PATCH v4.4-rc8] radeon: r100: Silence 'may be used uninitialized' warnings

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Message-ID: <CADnq5_Pgic5H-tyNKSA2Jfo6uOo7VDF3xoLSYDx9RNC6EkkQ+A@mail.gmail.com>
Date:	Fri, 8 Jan 2016 12:21:33 -0500
From:	Alex Deucher <alexdeucher@...il.com>
To:	Tim Gardner <tim.gardner@...onical.com>
Cc:	Maling list - DRI developers <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>
Subject: Re: [PATCH v4.4-rc8] radeon: r100: Silence 'may be used
 uninitialized' warnings

On Thu, Jan 7, 2016 at 12:31 PM,  <tim.gardner@...onical.com> wrote:
> From: Tim Gardner <tim.gardner@...onical.com>
>
>   CC [M]  drivers/gpu/drm/radeon/r100.o
> In file included from drivers/gpu/drm/radeon/radeon_mode.h:37:0,
>                  from drivers/gpu/drm/radeon/radeon.h:80,
>                  from drivers/gpu/drm/radeon/r100.c:33:
> drivers/gpu/drm/radeon/r100.c: In function 'r100_bandwidth_update':
> include/drm/drm_fixed.h:64:13: warning: 'crit_point_ff.full' may be used uninitialized in this function [-Wmaybe-uninitialized]
>   u64 tmp = ((u64)A.full << 13);
>              ^
> drivers/gpu/drm/radeon/r100.c:3153:63: note: 'crit_point_ff.full' was declared here
>   fixed20_12 peak_disp_bw, mem_bw, pix_clk, pix_clk2, temp_ff, crit_point_ff;
>                                                                ^
> drivers/gpu/drm/radeon/r100.c:3583:42: warning: 'disp_drain_rate.full' may be used uninitialized in this function [-Wmaybe-uninitialized]
>      temp_ff.full = read_return_rate.full - disp_drain_rate.full;
>
> gcc version 5.3.1 20151219 (Ubuntu 5.3.1-4ubuntu1)
>
> Cc: Alex Deucher <alexander.deucher@....com>
> Cc: "Christian König" <christian.koenig@....com>
> Cc: David Airlie <airlied@...ux.ie>
> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
> ---
>
> I think this warning is bogus, but I don't know how else to make gcc shut up.

It's definitely bogus.  It just showed up in a new version of gcc.  Applied.

Thanks.

Alex

>
>  drivers/gpu/drm/radeon/r100.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
> index 9e7e2bf..5eae0a8 100644
> --- a/drivers/gpu/drm/radeon/r100.c
> +++ b/drivers/gpu/drm/radeon/r100.c
> @@ -3150,7 +3150,8 @@ void r100_bandwidth_update(struct radeon_device *rdev)
>  {
>         fixed20_12 trcd_ff, trp_ff, tras_ff, trbs_ff, tcas_ff;
>         fixed20_12 sclk_ff, mclk_ff, sclk_eff_ff, sclk_delay_ff;
> -       fixed20_12 peak_disp_bw, mem_bw, pix_clk, pix_clk2, temp_ff, crit_point_ff;
> +       fixed20_12 peak_disp_bw, mem_bw, pix_clk, pix_clk2, temp_ff;
> +       fixed20_12 crit_point_ff = {0};
>         uint32_t temp, data, mem_trcd, mem_trp, mem_tras;
>         fixed20_12 memtcas_ff[8] = {
>                 dfixed_init(1),
> @@ -3204,7 +3205,7 @@ void r100_bandwidth_update(struct radeon_device *rdev)
>         fixed20_12 min_mem_eff;
>         fixed20_12 mc_latency_sclk, mc_latency_mclk, k1;
>         fixed20_12 cur_latency_mclk, cur_latency_sclk;
> -       fixed20_12 disp_latency, disp_latency_overhead, disp_drain_rate,
> +       fixed20_12 disp_latency, disp_latency_overhead, disp_drain_rate = {0},
>                 disp_drain_rate2, read_return_rate;
>         fixed20_12 time_disp1_drop_priority;
>         int c;
> --
> 1.9.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

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