Re: [PATCH] Fix application of sizeof to pointer

From: David Hildenbrand <david@redhat.com>
To: davidcomponentone@gmail.com, akpm@linux-foundation.org
Cc: shuah@kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
	Zeal Robot <zealci@zte.com.cn>
Subject: Re: [PATCH] Fix application of sizeof to pointer
Date: Tue, 12 Oct 2021 09:01:29 +0200	[thread overview]
Message-ID: <3ee52f17-0357-a99a-352e-424bfcc07f27@redhat.com> (raw)
In-Reply-To: <20211012030116.184027-1-davidcomponentone@gmail.com>

On 12.10.21 05:01, davidcomponentone@gmail.com wrote:
> From: David Yang <davidcomponentone@gmail.com>
> 
> The coccinelle check report:
> "./tools/testing/selftests/vm/split_huge_page_test.c:344:36-42:
> ERROR: application of sizeof to pointer"
> Using the "strlen" to fix it.
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: David Yang <davidcomponentone@gmail.com>
> ---
>   tools/testing/selftests/vm/split_huge_page_test.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vm/split_huge_page_test.c b/tools/testing/selftests/vm/split_huge_page_test.c
> index 1af16d2c2a0a..52497b7b9f1d 100644
> --- a/tools/testing/selftests/vm/split_huge_page_test.c
> +++ b/tools/testing/selftests/vm/split_huge_page_test.c
> @@ -341,7 +341,7 @@ void split_file_backed_thp(void)
>   	}
>   
>   	/* write something to the file, so a file-backed THP can be allocated */
> -	num_written = write(fd, tmpfs_loc, sizeof(tmpfs_loc));
> +	num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
>   	close(fd);
>   
>   	if (num_written < 1) {
> 

I think the code really just wants to write anything to the file that 
will be >= 1, which is also the case with this weird usage of sizeof.

As an alternative, I think we can just write anything else to the file

num_written = write(fd, (void *)&fd, sizeof(fd));

or

num_written = write(fd, "1", 1);

If I am not wrong/

-- 
Thanks,

David / dhildenb