Re: [PATCH] [v2] printk: avoid -Wsometimes-uninitialized warning

Chris Down
2021-10-04T12:31:36Z

Petr Mladek writes:
>On Tue 2021-09-28 11:17:26, Chris Down wrote:
>> Arnd Bergmann writes:
>> > From: Arnd Bergmann <arnd@arndb.de>
>> >
>> > clang notices that the pi_get_entry() function would use
>> > uninitialized data if it was called with a non-NULL module
>> > pointer on a kernel that does not support modules:
>> >
>> > kernel/printk/index.c:32:6: error: variable 'nr_entries' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>> > if (!mod) {
>> > ^~~~
>> > kernel/printk/index.c:38:13: note: uninitialized use occurs here
>> > if (pos >= nr_entries)
>> > ^~~~~~~~~~
>> > kernel/printk/index.c:32:2: note: remove the 'if' if its condition is always true
>> > if (!mod) {
>> >
>> > Rework the condition to make it clear to the compiler that we are always
>> > in the second case. Unfortunately the #ifdef is still required as the
>> > definition of 'struct module' is hidden when modules are disabled.
>> >
>> > Fixes: 337015573718 ("printk: Userspace format indexing support")
>>
>> This changelog should make it clear that this is theoretical and will never
>> actually happen, which is salient information for people who are considering
>> whether it should go in stable or similar.
>
>IMHO, the sentence "Rework the condition to make it clear that this
>is theoretical and will never actually happen" is rather clear.

Sounds good to me, thanks!

I guess it's unneeded at this point, but feel free to add:

Acked-by: Chris Down <chris@chrisdown.name>

>Well, I am not a native speaker.
>
>Anyway, I have pushed the patch into printk/linux.git, branch
>for-5.16.
>
>Best Regards,
>Petr