2015-06-04 10:40:04

by Sergei Zviagintsev

Subject: [PATCH] kdbus: use parentheses in KDBUS_ITEM_FOREACH macro uniformly

_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.

Signed-off-by: Sergei Zviagintsev <[email protected]>
---
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

2015-06-04 11:29:27

by David Herrmann

Subject: Re: [PATCH] kdbus: use parentheses in KDBUS_ITEM_FOREACH macro uniformly

Hi

On Thu, Jun 4, 2015 at 12:39 PM, Sergei Zviagintsev <[email protected]> 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.
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 <[email protected]>
> ---
> 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
>

2015-06-04 11:47:48

by Sergei Zviagintsev

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