> -----Original Message----- > From: linux-omap-owner@xxxxxxxxxxxxxxx > [mailto:linux-omap-owner@xxxxxxxxxxxxxxx] On Behalf Of Niels de Vos > Sent: Tuesday, May 10, 2011 2:51 PM > To: linux-omap@xxxxxxxxxxxxxxx > Cc: linux-fbdev@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; Niels de Vos > Subject: [PATCH] omap2/omapfb: make DBG() more resistant in > if-else constructions > > When DBG() is used in a simple if-else, the resulting code path > currently depends on the definition of DBG(). Inserting the > statement in > a "do { ... } while (0)" prevents this possible misuse. > > Signed-off-by: Niels de Vos <ndevos@xxxxxxxxxx> > > --- > Note, I have not found any offenders, but a mistake can > easily be made. > The following example shows what can go wrong if little intention is > paid to the definition of the DBG() macro. > > Example: > if something_went_wrong() > DBG("oh no, something went wrong!\n"); > else > printk("all went fine\n"); > > Old result where the else is placed inside the first if-statment: > if something_went_wrong() { > if (omapfb_debug) { > printk(KERN_DEBUG "oh no, something > went wrong!\n"); > } else { > printk("all went fine\n"); > } > } > > New result where the else is an alternative to the first if-statement: > if something_went_wrong() { > do { > if (omapfb_debug) > printk(KERN_DEBUG "oh no, > something went wrong!\n"); > } while (0); > } else { > printk("all went fine\n"); > } > --- > drivers/video/omap2/omapfb/omapfb.h | 6 ++++-- > 1 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/video/omap2/omapfb/omapfb.h > b/drivers/video/omap2/omapfb/omapfb.h > index 1305fc9..a01b0bb 100644 > --- a/drivers/video/omap2/omapfb/omapfb.h > +++ b/drivers/video/omap2/omapfb/omapfb.h > @@ -34,8 +34,10 @@ > #ifdef DEBUG > extern unsigned int omapfb_debug; > #define DBG(format, ...) \ > - if (omapfb_debug) \ > - printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__) > + do { \ > + if (omapfb_debug) \ > + printk(KERN_DEBUG "OMAPFB: " format, ## > __VA_ARGS__); \ > + while (0) A real good find. Wondering if it really didn't create any problems so far... ~sanjeev > #else > #define DBG(format, ...) > #endif > -- > 1.7.4.4 > > -- > To unsubscribe from this list: send the line "unsubscribe > linux-omap" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
