2022-03-31 15:51:04

by Alaa Mohamed

Subject: [PATCH] staging: gdm724x: Fix Duplication of Side Effects

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 <[email protected]>
---
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); })

static struct tty_driver *gdm_driver[TTY_MAX_COUNT];
static struct gdm *gdm_table[TTY_MAX_COUNT][GDM_TTY_MINOR];
--
2.35.1

2022-03-31 16:02:34

by David Laight

Subject: RE: [PATCH] staging: gdm724x: Fix Duplication of Side Effects

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 <[email protected]>
> ---
> 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

David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

2022-03-31 17:30:17

by Greg KH

Subject: Re: [PATCH] staging: gdm724x: Fix Duplication of Side Effects

On Thu, Mar 31, 2022 at 12:18:49PM +0200, Alaa Mohamed wrote:
> Fix Duplication of Side Effects for GDM_TTY_READY(gdm) macro
> reported by checkpatch
> "CHECK: Macro argument reuse 'gdm' - possible side-effects?"

There are no such side-effects here, sorry. Please always evaluate the
code to see what it does, checkpatch sometimes gets it wrong.

thanks,

greg k-h

2022-04-01 14:33:33

by Dan Carpenter

Subject: Re: [PATCH] staging: gdm724x: Fix Duplication of Side Effects

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 <[email protected]>
> > ---
> > 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.

regards,
dan carpenter

2022-04-02 13:56:04

by David Laight

Subject: RE: [PATCH] staging: gdm724x: Fix Duplication of Side Effects

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 <[email protected]>
> > > ---
> > > 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.

The 'gdm' and '_gdm' would need swapping over.
But, as you said, just:
#define GDM_TTY_READY(gdm) ((gdm) && (gdm)->tty_dev && (gdm)->port.count)
is fine - I'd add the () but not worry about multiple evaluation.

David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)