Re: [PATCH v4 1/2] xen: x86: irq: initialize irq desc in create_irq()

[Jan Beulich <jbeulich@suse.com>]

On 07.04.2025 18:46, Volodymyr Babchuk wrote:
> 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>

Just one other remark here: Personally I dislike the use of multiple or otherwise
excessive patch subject prefixes. xen/x86/irq: or even x86/irq: would have been
better here, imo.

Jan