x86/cpuid: Fix build with CentOS 6 following c/s 7479151106

[Xen-devel] [PATCH] x86/cpuid: Fix build with CentOS 6 following c/s 7479151106

Posted by Andrew Cooper 4 years, 7 months ago

GCC of a CentOS 6 vintage complains:

  cpuid.c: In function 'parse_xen_cpuid':
  cpuid.c:32: error: 'mid' may be used uninitialized in this function

This can't occur in practice because the while() loop is guarenteed to be
entered, but initialise mid to work around the issues.

Spotted by Gitlab CI.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index 36b1e2ce4c..acba0f7583 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -29,7 +29,7 @@ static int __init parse_xen_cpuid(const char *s)
             const char *name;
             unsigned int bit;
         } features[] __initconstrel = INIT_FEATURE_NAMES;
-        const struct feature *lhs, *mid, *rhs;
+        const struct feature *lhs, *rhs, *mid = NULL /* GCC... */;
         const char *feat;
 
         ss = strchr(s, ',');
-- 
2.11.0


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Re: [Xen-devel] [PATCH] x86/cpuid: Fix build with CentOS 6 following c/s 7479151106

Posted by Jan Beulich 4 years, 7 months ago

On 09.09.2019 17:55, Andrew Cooper wrote:
> GCC of a CentOS 6 vintage complains:
> 
>   cpuid.c: In function 'parse_xen_cpuid':
>   cpuid.c:32: error: 'mid' may be used uninitialized in this function
> 
> This can't occur in practice because the while() loop is guarenteed to be
> entered, but initialise mid to work around the issues.
> 
> Spotted by Gitlab CI.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Ah, yes, thanks. I too had noticed this yesterday, but didn't get
around to check what the correct workaround would be.

Acked-by: Jan Beulich <jbeulich@suse.com>

Jan

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