On Thu, Mar 31, 2022 at 10:49:24AM +0000, David Laight wrote:
> From: Dan Carpenter
> > Sent: 31 March 2022 11:40
> >
> > On Thu, Mar 31, 2022 at 10:29:04AM +0000, David Laight wrote:
> > > From: Alaa Mohamed
> > > > Sent: 31 March 2022 11:19
> > > >
> > > > Fix Duplication of Side Effects for GDM_TTY_READY(gdm) macro
> > > > reported by checkpatch
> > > > "CHECK: Macro argument reuse 'gdm' - possible side-effects?"
> > > >
> > > > Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@xxxxxxxxx>
> > > > ---
> > > > drivers/staging/gdm724x/gdm_tty.c | 4 +++-
> > > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
> > > > index 04df6f9f5403..6f0274470e69 100644
> > > > --- a/drivers/staging/gdm724x/gdm_tty.c
> > > > +++ b/drivers/staging/gdm724x/gdm_tty.c
> > > > @@ -27,7 +27,9 @@
> > > >
> > > > #define MUX_TX_MAX_SIZE 2048
> > > >
> > > > -#define GDM_TTY_READY(gdm) (gdm && gdm->tty_dev && gdm->port.count)
> > > > +#define GDM_TTY_READY(_gdm) \
> > > > + ({ typeof(_gdm) (gdm) = (_gdm); \
> > > > + (gdm && gdm->tty_dev && gdm->port.count); })
> > >
> > > Did you test this?
> > >
> > > see https://godbolt.org/z/cazPrrzPv
> > >
> >
> > I don't understand the link. The patch should work as far as I can see.
>
> If you call GDM_TTY_READY(gdm) the first line ends up as:
> struct xxx *gdm = gdm;
> which shadows the parameter.
> There's probably a warning about an uninitialised variable as well.
Oh yeah. You're right. But you won't get any variable uninitialized
warnings because int foo = foo; was the traditional way to silence GCC's
uninitialized variable warnings.
Smatch copied the GCC code. There are some static checkers which might
complain. Sparse used to have a warning about shadow variables but it
didn't trigger on this code. Not sure why.
regards,
dan carpenter
