Re: [PATCH] omap3isp: ispqueue: Fix uninitialized variable compiler warnings

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sakari,

On Saturday 05 January 2013 00:51:36 Sakari Ailus wrote:
> On Mon, Dec 17, 2012 at 09:52:48AM +0100, Laurent Pinchart wrote:
> > drivers/media/platform/omap3isp/ispqueue.c:399:18: warning: 'pa' may be
> > used uninitialized in this function [-Wuninitialized]
> > 
> > This is a false positive but the compiler has no way to know about it,
> > so initialize the variable to 0.
> > 
> > drivers/media/platform/omap3isp/ispqueue.c:445:6: warning:
> > 'vm_page_prot' may be used uninitialized in this function
> > [-Wuninitialized]
> > 
> > This is a false positive and the compiler should know better. Use
> > uninitialized_var().
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> > 
> >  drivers/media/platform/omap3isp/ispqueue.c |    4 ++--
> >  1 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/media/platform/omap3isp/ispqueue.c
> > b/drivers/media/platform/omap3isp/ispqueue.c index 15bf3ea..1388eb7
> > 100644
> > --- a/drivers/media/platform/omap3isp/ispqueue.c
> > +++ b/drivers/media/platform/omap3isp/ispqueue.c
> > @@ -366,7 +366,7 @@ static int isp_video_buffer_prepare_pfnmap(struct
> > isp_video_buffer *buf)
> >  	unsigned long this_pfn;
> >  	unsigned long start;
> >  	unsigned long end;
> > -	dma_addr_t pa;
> > +	dma_addr_t pa = 0;
> 
> Why 0 and not something else arbitrary? :-)
> 
> The value will not be used as far as I can tell. If it gets used it
> certainly is a bug.

If buf->vbuf.length == 0 pa will be used uninitialized. This is clearly a bug, 
but I thought it would be easier to debug if pa was set to 0 in that case 
instead of a random value through uninitialized_var().

> >  	int ret = -EFAULT;
> >  	
> >  	start = buf->vbuf.m.userptr;
> > 
> > @@ -419,7 +419,7 @@ done:
> >  static int isp_video_buffer_prepare_vm_flags(struct isp_video_buffer
> >  *buf)
> >  {
> >  	struct vm_area_struct *vma;
> > -	pgprot_t vm_page_prot;
> > +	pgprot_t uninitialized_var(vm_page_prot);
> >  	unsigned long start;
> >  	unsigned long end;
> >  	int ret = -EFAULT;

-- 
Regards,

Laurent Pinchart