From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH 1/1] XEN: enlighten, use uninitialized_var(cx) Date: Wed, 26 Aug 2009 08:09:25 +0200 Message-ID: <20090826060925.GA6194@elte.hu> References: <1251234044-6943-1-git-send-email-jirislaby@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1251234044-6943-1-git-send-email-jirislaby@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Jiri Slaby Cc: jeremy@xensource.com, chrisw@sous-sol.org, virtualization@lists.osdl.org, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org * Jiri Slaby wrote: > To avoid a wrong compiler warning, use unitialized_var(cx) in > xen_init_cpuid_mask. > > cx needn't be initialized for cpuid when ax is 1. > > Signed-off-by: Jiri Slaby > Cc: Jeremy Fitzhardinge > Cc: Chris Wright > --- > arch/x86/xen/enlighten.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c > index e90540a..5ab75e2 100644 > --- a/arch/x86/xen/enlighten.c > +++ b/arch/x86/xen/enlighten.c > @@ -202,7 +202,7 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, > > static __init void xen_init_cpuid_mask(void) > { > - unsigned int ax, bx, cx, dx; > + unsigned int ax, bx, uninitialized_var(cx), dx; Please dont use uninitialized_var(), it's an unreliable facility: if this variable ever grows a real used-without-initialization bug in the future, the compiler warning is turned off permanently. It's rare but might happen. We are better off with initializing it to zero. Ingo