[PATCH] drm: avoid "mono_time_offset may be used uninitialized"

[Stephen Warren]

On 01/29/2013 05:09 PM, Stephen Warren wrote:
> From: Stephen Warren 
> 
> Silence the following:
> drivers/gpu/drm/drm_irq.c: In function 
> 'drm_calc_vbltimestamp_from_scanoutpos':
> drivers/gpu/drm/drm_irq.c:583:24: warning: 'mono_time_offset.tv64' may be 
> used uninitialized in this function

FYI, I found that I see this warning with gcc-4.5.3, but not with
gcc-4.7.2 or gcc-4.6.3. Hence, you might decide you don't care about
this patch.

[PATCH] drm: avoid "mono_time_offset may be used uninitialized"

[Stephen Warren]

From: Stephen Warren 

Silence the following:
drivers/gpu/drm/drm_irq.c: In function 'drm_calc_vbltimestamp_from_scanoutpos':
drivers/gpu/drm/drm_irq.c:583:24: warning: 'mono_time_offset.tv64' may be used 
uninitialized in this function

... by always initializing mono_time_offset to zero. In practice, this
warning is false, since mono_time_offset is both set and used under the
condition if (!drm_timestamp_monotonic). However, at least my compiler
can't be coerced into realizing this; almost any code between the if
blocks that set and use the variable causes this warning.

Signed-off-by: Stephen Warren 
---
I'm not sure what the current thinking is re: silencing warnings like this;
IIRC some people may dislike this kind of change. Perhaps if this change
alone is problematic, one could additionally remove the if condition on the
use of mono_time_offset, thus always using the value?
---
 drivers/gpu/drm/drm_irq.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 19c01ca..b199818 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -580,7 +580,7 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device 
*dev, int crtc,
  unsigned flags,
  struct drm_crtc *refcrtc)
 {
-   ktime_t stime, etime, mono_time_offset;
+   ktime_t stime, etime, mono_time_offset = {0};
struct timeval tv_etime;
struct drm_display_mode *mode;
int vbl_status, vtotal, vdisplay;
-- 
1.7.10.4

[PATCH] drm: avoid mono_time_offset may be used uninitialized

[Stephen Warren]

From: Stephen Warren swar...@nvidia.com

Silence the following:
drivers/gpu/drm/drm_irq.c: In function 'drm_calc_vbltimestamp_from_scanoutpos':
drivers/gpu/drm/drm_irq.c:583:24: warning: 'mono_time_offset.tv64' may be used 
uninitialized in this function

... by always initializing mono_time_offset to zero. In practice, this
warning is false, since mono_time_offset is both set and used under the
condition if (!drm_timestamp_monotonic). However, at least my compiler
can't be coerced into realizing this; almost any code between the if
blocks that set and use the variable causes this warning.

Signed-off-by: Stephen Warren swar...@nvidia.com
---
I'm not sure what the current thinking is re: silencing warnings like this;
IIRC some people may dislike this kind of change. Perhaps if this change
alone is problematic, one could additionally remove the if condition on the
use of mono_time_offset, thus always using the value?
---
 drivers/gpu/drm/drm_irq.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 19c01ca..b199818 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -580,7 +580,7 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device 
*dev, int crtc,
  unsigned flags,
  struct drm_crtc *refcrtc)
 {
-   ktime_t stime, etime, mono_time_offset;
+   ktime_t stime, etime, mono_time_offset = {0};
struct timeval tv_etime;
struct drm_display_mode *mode;
int vbl_status, vtotal, vdisplay;
-- 
1.7.10.4

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