[PATCH] Hide 0 size passed to memset/bzero from compiler

[H.J. Lu]

On Tue, Dec 17, 2024 at 11:02 PM Sam James <sam@gentoo.org> wrote:
>
> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
> > Hide 0 size passed to memset/bzero from compiler since compiler may reject
> > 0 size.  Clang 19 issues an error in such case:
> >
> > ./tester.c:1345:29: error: 'size' argument to memset is '0'; did you mean to transpose the last two arguments? [-Werror,-Wmemset-transposed-args]
> >  1345 |   (void) memset(one+2, 'y', 0);
> >       |                             ^
> > ./tester.c:1345:29: note: parenthesize the third argument to silence
> > ./tester.c:1432:16: error: 'size' argument to bzero is '0' [-Werror,-Wsuspicious-bzero]
> >  1432 |   bzero(one+2, 0);
> >       |                ^
> > ./tester.c:1432:16: note: parenthesize the second argument to silence
> >
> > Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
>
> OK, although I don't know if we want to do the similar trick as for
> *alloc. But not required.

I will do that for consistency.

Thanks.

>
> > ---
> >  string/tester.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/string/tester.c b/string/tester.c
> > index ee96747280..ae0c6a5541 100644
> > --- a/string/tester.c
> > +++ b/string/tester.c
> > @@ -69,6 +69,10 @@ DIAG_IGNORE_NEEDS_COMMENT (7, "-Wstringop-overflow=");
> >  const char *it = "<UNSET>";  /* Routine name for message routines. */
> >  size_t errors = 0;
> >
> > +/* NB: Hide 0 size from compiler since compiler may reject 0 size passed
> > +   to memset and bzero.  */
> > +size_t size_zero = 0;
> > +
> >  /* Complain if condition is not true.  */
> >  static void
> >  check (int thing, int number)
> > @@ -1342,7 +1346,7 @@ test_memset (void)
> >    check(memset(one+1, 'x', 3) == one+1, 1);  /* Return value. */
> >    equal(one, "axxxefgh", 2);         /* Basic test. */
> >
> > -  (void) memset(one+2, 'y', 0);
> > +  (void) memset(one+2, 'y', size_zero);
> >    equal(one, "axxxefgh", 3);         /* Zero-length set. */
> >
> >    (void) memset(one+5, 0, 1);
> > @@ -1429,7 +1433,7 @@ test_bzero (void)
> >    equal(one+4, "ef", 3);
> >
> >    (void) strcpy(one, "abcdef");
> > -  bzero(one+2, 0);
> > +  bzero(one+2, size_zero);
> >    equal(one, "abcdef", 4);           /* Zero-length copy. */
> >  }



-- 
H.J.