xen: x86: irq: initialize irq desc in create_irq()

While building xen with GCC 14.2.1 with "-fcondition-coverage" option
or with "-Og", the compiler produces a false positive warning:

  arch/x86/irq.c: In function ‘create_irq’:
  arch/x86/irq.c:281:11: error: ‘desc’ may be used uninitialized [-Werror=maybe-uninitialized]
    281 |     ret = init_one_irq_desc(desc);
        |           ^~~~~~~~~~~~~~~~~~~~~~~
  arch/x86/irq.c:269:22: note: ‘desc’ was declared here
    269 |     struct irq_desc *desc;
        |                      ^~~~
  cc1: all warnings being treated as errors
  make[2]: *** [Rules.mk:252: arch/x86/irq.o] Error 1

While we have signed/unsigned comparison both in "for" loop and in
"if" statement, this still can't lead to use of uninitialized "desc",
as either loop will be executed at least once, or the function will
return early. So this is a clearly false positive warning due to a
bug [1] in GCC.

Initialize "desc" with NULL to make GCC happy.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119665

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: 7a4484d90b3003171f1700e424ad45b931200ba6
master date: 2025-04-08 09:40:39 +0200

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 6b1f338eae7cd3cdf99c57c17ae75d7b031b0fa1..db2d574680eaafb534214ac8b1f7655861c1a2cf 100644 (file)
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -261,7 +261,7 @@ void __init clear_irq_vector(int irq)
 int create_irq(nodeid_t node, bool grant_access)
 {
     int irq, ret;
-    struct irq_desc *desc;
+    struct irq_desc *desc = NULL ; /* gcc14 -Og or -fcondition-coverage */
 
     for (irq = nr_irqs_gsi; irq < nr_irqs; irq++)
     {