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_babc...@epam.com>
---
Changes in v4:
- Reverted back to initialing desc, per Jan's request
- Added link to the corresponding GCC bug
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index dd8d921f18..38ac0823d7 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -265,7 +265,7 @@ 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++)
{
--
2.48.1
