linux-kernel - Re: [PATCH 04/12] selftests/mm: fix a char* assignment in mlock2-tests.c

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Date:   Fri, 2 Jun 2023 11:24:52 -0400
From:   Peter Xu <peterx@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/12] selftests/mm: fix a char* assignment in
 mlock2-tests.c

On Fri, Jun 02, 2023 at 12:04:57PM +0200, David Hildenbrand wrote:
> On 02.06.23 03:33, John Hubbard wrote:
> > The stop variable is a char*, so use "\0" when assigning to it, rather
> > than attempting to assign a character type. This was generating a
> > warning when compiling with clang.
> > 
> > Signed-off-by: John Hubbard <jhubbard@...dia.com>
> > ---
> >   tools/testing/selftests/mm/mlock2-tests.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/mm/mlock2-tests.c b/tools/testing/selftests/mm/mlock2-tests.c
> > index 11b2301f3aa3..8ee95077dc25 100644
> > --- a/tools/testing/selftests/mm/mlock2-tests.c
> > +++ b/tools/testing/selftests/mm/mlock2-tests.c
> > @@ -50,7 +50,7 @@ static int get_vm_area(unsigned long addr, struct vm_boundaries *area)
> >   			printf("cannot parse /proc/self/maps\n");
> >   			goto out;
> >   		}
> > -		stop = '\0';
> > +		stop = "\0";
> >   		sscanf(line, "%lx", &start);
> >   		sscanf(end_addr, "%lx", &end);
> 
> 
> I'm probably missing something, but what is the stop variable supposed to do
> here? It's completely unused, no?
> 
> if (!strchr(end_addr, ' ')) {
> 	printf("cannot parse /proc/self/maps\n");
> 	goto out;
> }

I guess it wanted to do "*stop = '\0'" but it just didn't matter a lot
since the sscanf() just worked..

-- 
Peter Xu