On Friday 18 March 2016 16:13:28 Vineet Gupta wrote: > On Friday 18 March 2016 03:59 PM, Arnd Bergmann wrote: > > On Friday 18 March 2016 15:50:11 Vineet Gupta wrote: > >> Sure, but I prefer this to be only for gcc 4.8 as this warning seems to be > >> healthy in small doses At least it keeps the door open for future discussion > >> with gcc guys ! > > > > FWIW, testing on ARM with gcc-6.0 -O3, I also get tons of maybe-uninitialized > > warnings. It's unlikely that this is architecture specific or fixed in newer > > compiler versions. > > So we disable this for good just like -Os. > What a shame - seemed like a reasonable safety net for programming errors. Yes, it's an immensely useful warning, if you manage to avoid the false positives. > >> The following nested construct actually works - does that look OK to you ? > >> > >> ARCH_CFLAGS += -O3 $(call cc-ifversion, -lt, 0408, $(call cc-disable-warning,maybe-uninitialized,)) > > > > Yes, that seems ok. > > There was typo actually -lt needed to be -eq > > > I don't really understand why -O3 is needed though, maybe it's better to > > assume that it won't be needed in future gcc versions and do > > Not sure what you mean, -O3 for triggering the warnings or -O3 in ARC makefile at all. > Assuming it's latter, this is how its been forever and was added consciously as > performance seemed better with -O3 than the default -O2. I think it's dangerous to use -O3 in one architecture when nothing else uses it. If you don't have a strong reason to use -O3, maybe just drop that use the default -O2 -Wmaybe-uninitialized like everyone else does. On a related note, I have submitted a patch that turns CONFIG_CC_OPTIMIZE_FOR_SIZE into a choice statement, so we actually get the -Wmaybe-uninitialized warnings in an allyesconfig or allmodconfig build. It would be trivial to extend that to give the choice between -Os, -O2 and -O3, and then pick -O3 in a defconfig, over the -O2 default. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
