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Date: Mon, 26 Oct 2009 12:21:11 +0100 From: Ingo Molnar <mingo@...e.hu> To: Pekka Enberg <penberg@...helsinki.fi>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Paul Mackerras <paulus@...ba.org>, Frédéric Weisbecker <fweisbec@...il.com>, Arnaldo Carvalho de Melo <acme@...hat.com> Cc: Paul Mundt <lethal@...ux-sh.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] perf tools: Kill off -Wcast-align * Pekka Enberg <penberg@...helsinki.fi> wrote: > * Paul Mundt <lethal@...ux-sh.org> wrote: > >> > The present use of -Wcast-align causes the build to blow up on SH due to > >> > generating a "cast increases required alignment of target type" error on > >> > each invocation of list_for_each_entry(). > >> > > >> > It seems that this was previously reported and killed off in the ia64 > >> > support patch, but nothing seems to have happened with that. Presumably > >> > the same problem still remains there, too. > >> > > >> > Signed-off-by: Paul Mundt <lethal@...ux-sh.org> > > On Mon, Oct 26, 2009 at 07:25:20AM +0100, Ingo Molnar wrote: > >> Is this a GCC bug producing false positive warnings? The GCC manpage > >> says: > >> > >> -Wcast-align > >> Warn whenever a pointer is cast such that the required alignment of the > >> target is increased. For example, warn if a "char *" is cast to an > >> "int *" on machines where integers can only be accessed at two- or > >> four-byte boundaries. > >> > >> Which looks moderately useful - if it works. > > On Mon, Oct 26, 2009 at 11:47 AM, Paul Mundt <lethal@...ux-sh.org> wrote: > > > Well, both ia64 and sh have hit this in the current compilers, and > > it doesn't seem to pose any code generation issues. In the areas > > where it is generated it seems to relate to 64-bit data types in the > > data structures, which in itself doesn't seem inherently > > problematic. > > > > I'll submit a bug report to the GCC folks, but for the time being > > given that multiple architectures are hitting this and it doesn't > > seem to be causing any issues, it would be better to have this flag > > dropped. > > Can we disable the flag for affected architectures but keep it enabled > for x86? For now i've applied Paul's fix - x86 doesnt have such type restrictions and i dont remember this warning having flagged some real data structure alignment bug anywhere. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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