linux-kernel - Re: [PATCH] char: fix sparse variable shadowing and int as NULL pointer in rocket.c

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Date:	Wed, 27 Feb 2008 15:38:07 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] char: fix sparse variable shadowing and int as NULL
	pointer in rocket.c

On Wed, 2008-02-27 at 15:29 -0800, Andrew Morton wrote:
> On Fri, 22 Feb 2008 09:46:59 -0800
> Harvey Harrison <harvey.harrison@...il.com> wrote:
> >
> > Subject: [PATCH] char: fix sparse variable shadowing and int as NULL pointer in rocket.c
> >
> 
> Please try to make the patch titles big-endian.  This one could have been
> 
> char: rocket.c: fix sparse variable shadowing and int as NULL pointer
> 

OK.

> or even
> 
> rocket.c: fix sparse variable shadowing and int as NULL pointer
> 
> > Nested min() macros shadow _x, separate into two lines.
> > drivers/char/rocket.c:451:7: warning: symbol '_x' shadows an earlier one
> > drivers/char/rocket.c:451:7: originally declared here
> > drivers/char/rocket.c:451:7: warning: symbol '_x' shadows an earlier one
> > drivers/char/rocket.c:451:7: originally declared here
> > drivers/char/rocket.c:451:7: warning: symbol '_y' shadows an earlier one
> > drivers/char/rocket.c:451:7: originally declared here
> > drivers/char/rocket.c:1754:7: warning: symbol '_x' shadows an earlier one
> > drivers/char/rocket.c:1754:7: originally declared here
> > drivers/char/rocket.c:1754:7: warning: symbol '_x' shadows an earlier one
> > drivers/char/rocket.c:1754:7: originally declared here
> > drivers/char/rocket.c:1754:7: warning: symbol '_y' shadows an earlier one
> > drivers/char/rocket.c:1754:7: originally declared here
> > drivers/char/rocket.c:1751:20: warning: Using plain integer as NULL pointer
> > 
> 
> That's really a sparse glitch.  There's nothing we can sanely do about it.
> 

Well, we can at least get rid of the warnings when min/max are nested.
I sent you a patch earlier today that uses different temp variables in
min/max/min_t/max_t to avoid this.  min/min and max/max nesting will
always see this.  I also introduced clamp()/clamp_t() in that patch
for use in libata and drivers/media.

> > ---
> >  drivers/char/rocket.c |    9 +++++----
> >  1 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/char/rocket.c b/drivers/char/rocket.c
> > index 72f2892..2778d64 100644
> > --- a/drivers/char/rocket.c
> > +++ b/drivers/char/rocket.c
> > @@ -448,7 +448,8 @@ static void rp_do_transmit(struct r_port *info)
> >  	while (1) {
> >  		if (tty->stopped || tty->hw_stopped)
> >  			break;
> > -		c = min(info->xmit_fifo_room, min(info->xmit_cnt, XMIT_BUF_SIZE - info->xmit_tail));
> > +		c = min(info->xmit_fifo_room, info->xmit_cnt);
> > +		c = min(c, XMIT_BUF_SIZE - info->xmit_tail);
> 
> Apart from things like that.
> 
> Probably this code is cleaner than the old version so let's do it, but it
> seems that we need a general fix.

min3()?  No _good_ ideas I'm afraid.

Cheers,

Harvey

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