Em Fri, Feb 28, 2014 at 10:29:23PM +0100, Peter Zijlstra escreveu: > On Fri, Feb 28, 2014 at 06:25:51PM -0300, Arnaldo Carvalho de Melo wrote: > > From: Jiri Olsa <[email protected]>
> > The gcc documentation offers workaround for valid aliasing by using > > __may_alias__ attribute: > > http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Type-Attributes.html > > Using this workaround for the find_first_bit function. > Hurm; didn't I suggest using -fno-strict-aliasing just like the kernel > does? Because the C aliasing rules are bonghits heavy? Either way would solve the problem at hand, I just used the smaller hammer offered. I thought that Ingo had something against this, but only reference I could find now about it was this: -------------------------------------------- commit 65014ab36196f6d86edc9ee23759d6930b9d89a8 Author: Ingo Molnar <[email protected]> Date: Wed Sep 2 14:55:55 2009 +0200 perf tools: Work around strict aliasing related warnings Older versions of GCC are rather stupid about strict aliasing: <SNIP> Make it clear to GCC that we intend with those pointers, by passing them through via an explicit (void *) cast. We might want to add -fno-strict-aliasing as well, like the kernel itself does. Cc: Peter Zijlstra <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Frederic Weisbecker <[email protected]> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <[email protected]> -------------------------------------------- Jiri's bandaid is for _newer_ compilers, so... - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
