Re: [PATCH] selftests/vm: silence uninitialized variable warning

[Mike Kravetz <mike.kravetz@oracle.com>]

On 07/19/22 12:42, Dan Carpenter wrote:
> This code just reads from memory without caring about the data itself.
> However static checkers complain that "tmp" is never properly
> initialized.  Initialize it to zero and change the name to "dummy" to
> show that we don't care about the value stored in it.
> 
> Fixes: c4b6cb884011 ("selftests/vm: add hugetlb madvise MADV_DONTNEED MADV_REMOVE test")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  tools/testing/selftests/vm/hugetlb-madvise.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Thanks Dan!

Your analysis is correct.  We do not care about the value returned, and
just want to trigger a read fault.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

> 
> diff --git a/tools/testing/selftests/vm/hugetlb-madvise.c b/tools/testing/selftests/vm/hugetlb-madvise.c
> index 6c6af40f5747..3c9943131881 100644
> --- a/tools/testing/selftests/vm/hugetlb-madvise.c
> +++ b/tools/testing/selftests/vm/hugetlb-madvise.c
> @@ -89,10 +89,11 @@ void write_fault_pages(void *addr, unsigned long nr_pages)
>  
>  void read_fault_pages(void *addr, unsigned long nr_pages)
>  {
> -	unsigned long i, tmp;
> +	unsigned long dummy = 0;
> +	unsigned long i;
>  
>  	for (i = 0; i < nr_pages; i++)
> -		tmp += *((unsigned long *)(addr + (i * huge_page_size)));

When I originally wrote this, something must have complained if written as:

	tmp = *((unsigned long *)(addr + (i * huge_page_size)));

changing to += eliminated that complaint, but caused this one.  Happy
with your changes, but if there is an even better way to write this, I am
happy to change it.

-- 
Mike Kravetz

> +		dummy += *((unsigned long *)(addr + (i * huge_page_size)));
>  }
>  
>  int main(int argc, char **argv)
> -- 
> 2.35.1
>