linux-kernel - Re: [PATCH] kdbus: use parentheses in KDBUS_ITEM

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Date:	Thu, 4 Jun 2015 14:47:43 +0300
From:	Sergei Zviagintsev <sergei@...v.net>
To:	David Herrmann <dh.herrmann@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kdbus: use parentheses in KDBUS_ITEM_FOREACH macro
 uniformly

Hi David,

On Thu, Jun 04, 2015 at 01:29:22PM +0200, David Herrmann wrote:
> Hi
> 
> On Thu, Jun 4, 2015 at 12:39 PM, Sergei Zviagintsev <sergei@...v.net> wrote:
> > _i is used as loop cursor and must be a proper lvalue, whereas two other
> > arguments can be complex expressions. Stay uniform across the macro and
> > enclose _is and _s with parentheses in all cases, but keep _i without
> > them (any valid lvalue will not break cast to (u8 *) due to precedence
> > rules). Update documentation example.
> >
> > List macroses (e.g. list_for_each) were taken as an example for this
> > change.
> 
> I'm not a big fan of this patch. Treating arguments differently just
> makes the macros harder to read, imo. Why not keep the parantheses
> around all arguments? It doesn't hurt and keeps the style consistent.

I agree, the point is just to keep things consistent. I'll send v2.

> Besides, lvalues might consist of more complex expressions, so I'm not
> sure this is even the right way to go.
> 
> Thanks
> David
> 
> > Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
> > ---
> >  Documentation/kdbus/kdbus.item.xml | 4 ++--
> >  ipc/kdbus/item.h                   | 6 +++---
> >  2 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/kdbus/kdbus.item.xml b/Documentation/kdbus/kdbus.item.xml
> > index b0eeeef995af..fb8b6c151a0d 100644
> > --- a/Documentation/kdbus/kdbus.item.xml
> > +++ b/Documentation/kdbus/kdbus.item.xml
> > @@ -73,8 +73,8 @@
> >
> >  #define KDBUS_ITEM_FOREACH(item, head, first)                      \
> >      for (item = (head)->first;                                     \
> > -         ((uint8_t *)(item) < (uint8_t *)(head) + (head)->size) && \
> > -          ((uint8_t *)(item) >= (uint8_t *)(head));                \
> > +         ((uint8_t *)item < (uint8_t *)(head) + (head)->size) &&   \
> > +          ((uint8_t *)item >= (uint8_t *)(head));                \
> >           item = KDBUS_ITEM_NEXT(item))
> >        ]]></programlisting>
> >      </refsect2>
> > diff --git a/ipc/kdbus/item.h b/ipc/kdbus/item.h
> > index 03612368b3bb..592b68a7c2db 100644
> > --- a/ipc/kdbus/item.h
> > +++ b/ipc/kdbus/item.h
> > @@ -28,9 +28,9 @@
> >  #define KDBUS_ITEM_PAYLOAD_SIZE(_i) ((_i)->size - KDBUS_ITEM_HEADER_SIZE)
> >
> >  #define KDBUS_ITEMS_FOREACH(_i, _is, _s)                               \
> > -       for (_i = _is;                                                  \
> > -            ((u8 *)(_i) < (u8 *)(_is) + (_s)) &&                       \
> > -              ((u8 *)(_i) >= (u8 *)(_is));                             \
> > +       for (_i = (_is);                                                \
> > +            ((u8 *)_i < (u8 *)(_is) + (_s)) &&                         \
> > +              ((u8 *)_i >= (u8 *)(_is));                               \
> >              _i = KDBUS_ITEM_NEXT(_i))
> >
> >  #define KDBUS_ITEM_VALID(_i, _is, _s)                                  \
> > --
> > 1.8.3.1
> >
--
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