Re: [PATCH] cpu: Remove pointless check

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On Wed, Apr 27, 2022 at 10:12:25AM +0200, Peter Krempa wrote:
On Wed, Apr 27, 2022 at 09:51:34 +0200, Martin Kletzander wrote:
These two pointers can never be NULL since they are initialised to a reference
of a struct.  This became apparent when commit 210a19539447 added a VIR_DEBUG
which used both pointers because due to the concise condition the compiler saw
that if the "and" part of the condition did short-circuit (and it assumed that
can happen) the second variable would not be initialised, but it is used in the
debugging message, so the build failed with:

  In file included from ../src/cpu/cpu_x86.c:27:
  ../src/cpu/cpu_x86.c: In function ‘virCPUx86DataIsIdentical’:
  ../src/util/virlog.h:79:5: error: ‘bdata’ may be used uninitialized in this
  function [-Werror=maybe-uninitialized]

Fix this by just assigning the helper pointers and remove the condition
altogether.

Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
---
Pushed under the build-breaker rule, but feel free to review/object.

Oops! Unfortunately neither my complilers:

clang version 13.0.0 (Fedora 13.0.0-3.fc35),
gcc (GCC) 11.2.1 20220127 (Red Hat 11.2.1-9)

nor the CI:

https://gitlab.com/pipo.sk/libvirt/-/pipelines/524030525 (besides the
usual macos-11 fail)

complained. Which compiler did you use?


gcc (Gentoo 11.3.0 p4) 11.3.0



 src/cpu/cpu_x86.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index 7e9d1cea47d1..a5eac7601cad 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -3314,10 +3314,8 @@ virCPUx86DataIsIdentical(const virCPUData *a,
         return VIR_CPU_COMPARE_INCOMPATIBLE;
     }

-    if (!((adata = &a->data.x86) && (bdata = &b->data.x86))) {
-        VIR_DEBUG("missing x86 data: a:%p b:%p", adata, bdata);
-        return VIR_CPU_COMPARE_ERROR;
-    }
+    adata = &a->data.x86;
+    bdata = &b->data.x86;

Yup, checking whether the result of the '&' operator is non-null doesn't
make sense.

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