Re: [PATCH 2/2] drm/i915: Compile time concatenate WARN_ON macro strings

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On pe, 2015-12-18 at 12:03 +0000, Dave Gordon wrote:
> On 18/12/15 10:39, Joonas Lahtinen wrote:
> > Using __stringify(x) instead of #x adds support for macros as
> > a parameter and reduces runtime overhead.
> > 
> > Slightly increases the .text size but should not matter.
> > 
> > v2:
> > - Define I915_STATE_WARN_ON though I915_STATE_WARN
> >    (Bikeshed inspiration by Chris)
> > 
> > Cc: Rob Clark <robdclark@gmail.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_drv.h | 14 ++++----------
> >   1 file changed, 4 insertions(+), 10 deletions(-)
> > 
> > 

<SNIP>

> > 					
> > \
> > -})
> > +#define I915_STATE_WARN_ON(x)					
> > 	\
> > +	I915_STATE_WARN((x), "WARN_ON(" __stringify(x) ")")
> > 
> >   static inline const char *yesno(bool v)
> >   {
> 
> NAK.
> 
> This will give compile-time warnings for lines such as:
> 
> 	WARN_ON(x%16 != 0);
> 
> because the stringified text of the expression (which in this case 
> contains a "%" character) would appear as part of the format string, 
> rather than inside an argument. See:
> 
> 4eee492 drm/i915: fix driver's versions of WARN_ON & WARN_ON_ONCE
> 

Great catch, I'll change it to have preceding "%s". Did not get any
compile-time warning though, this would be something caught by a
(rather advanced?) static analysis.

Regards, Joonas

> .Dave.
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation

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