Messages in this thread | | | Date | Thu, 6 Mar 2014 17:46:53 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 2/2] perf tools: Fix strict alias issue for find_first_bit |
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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 <jolsa@redhat.com>
> > 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:
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commit 65014ab36196f6d86edc9ee23759d6930b9d89a8 Author: Ingo Molnar <mingo@elte.hu> 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 <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> --------------------------------------------
Jiri's bandaid is for _newer_ compilers, so...
- Arnaldo
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