While building xen with GCC 14.2.1 with "-fcondition-coverage" option,
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
The same behavior can be observed when building Xen with "-Og"
optimization level. Fix this by using "do { } while" loop instead of
"for" loop.
Signed-off-by: Volodymyr Babchuk <volodymyr_babc...@epam.com>
---
Changes in v3:
- Correct code style ("do {")
- Add comment describing why we need do { } while loop.
I prefer to leave do {} while because Nicola Vetrini
said that this approach might help with MISRA Rule 9.1
without needing an explicit initializer.
Changes in v2:
- Use do { } while loop instead of initializing desc with NULL
---
xen/arch/x86/irq.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index dd8d921f18..2f288704b5 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -264,15 +264,24 @@ void __init clear_irq_vector(int irq)
int create_irq(nodeid_t node, bool grant_access)
{
- int irq, ret;
+ int ret;
+ int irq = nr_irqs_gsi;
struct irq_desc *desc;
- for (irq = nr_irqs_gsi; irq < nr_irqs; irq++)
- {
+ if ( irq >= nr_irqs )
+ return -ENOSPC;
+
+ /*
+ * do { } while loop is used here to convince gcc14 that 'desc' is
+ * really assigned. Otherwise with -Og or -fcondition-coverage it
+ * may throw an false error stating that 'desc' may be used before
+ * initialization.
+ */
+ do {
desc = irq_to_desc(irq);
if (cmpxchg(&desc->arch.used, IRQ_UNUSED, IRQ_RESERVED) == IRQ_UNUSED)
break;
- }
+ } while ( ++irq < nr_irqs );
if (irq >= nr_irqs)
return -ENOSPC;
--
2.48.1
