linux-kernel - Re: [PATCH] selftests/mm: Fix compiler -Wmaybe-uninitialized warning

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Message-ID: <9da46633-e9c1-42a7-b52b-16cf89836abc@redhat.com>
Date: Wed, 9 Apr 2025 11:57:51 +0200
From: David Hildenbrand <david@...hat.com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/mm: Fix compiler -Wmaybe-uninitialized warning

On 09.04.25 11:50, Anshuman Khandual wrote:
> Following build warning comes up for cow test as 'transferred' variable has
> not been initialized. Fix the warning via zero init for the variable.
> 
>    CC       cow
> cow.c: In function ‘do_test_vmsplice_in_parent’:
> cow.c:365:61: warning: ‘transferred’ may be used uninitialized [-Wmaybe-uninitialized]
>    365 |                 cur = read(fds[0], new + total, transferred - total);
>        |                                                 ~~~~~~~~~~~~^~~~~~~
> cow.c:296:29: note: ‘transferred’ was declared here
>    296 |         ssize_t cur, total, transferred;
>        |                             ^~~~~~~~~~~
>    CC       compaction_test
>    CC       gup_longterm
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kselftest@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>   tools/testing/selftests/mm/cow.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
> index f0cb14ea8608..b6cfe0a4b7df 100644
> --- a/tools/testing/selftests/mm/cow.c
> +++ b/tools/testing/selftests/mm/cow.c
> @@ -293,7 +293,7 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size,
>   		.iov_base = mem,
>   		.iov_len = size,
>   	};
> -	ssize_t cur, total, transferred;
> +	ssize_t cur, total, transferred = 0;
>   	struct comm_pipes comm_pipes;
>   	char *old, *new;
>   	int ret, fds[2];


if (before_fork) {
	transferred = vmsplice(fds[1], &iov, 1, 0);
...

if (!before_fork) {
	transferred = vmsplice(fds[1], &iov, 1, 0);
...

for (total = 0; total < transferred; total += cur) {
...


And I don't see any jump label that could jump to code that would ve 
using transferred.

What am I missing?

-- 
Cheers,

David / dhildenb