[dpdk-dev] [PATCH 1/2] Fix container_of() macro to work with const members

[dpdk-dev] [PATCH 1/2] Fix container_of() macro to work with const members

[Jan Blunck]

This fixes the usage of structure members that are declared const to get
a pointer to the embedding parent structure.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
---
 lib/librte_eal/common/include/rte_common.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index 8dda3e2..c421708 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -347,8 +347,9 @@ rte_bsf32(uint32_t v)
  */
 #ifndef container_of
 #define container_of(ptr, type, member)	__extension__ ({		\
-			typeof(((type *)0)->member) *_ptr = (ptr);	\
-			(type *)(((char *)_ptr) - offsetof(type, member)); })
+			const typeof(((type *)0)->member) *_ptr = (ptr); \
+			(type *)(((uintptr_t)_ptr) - offsetof(type, member)); \
+		})
 #endif
 
 #define _RTE_STR(x) #x
-- 
2.7.4

[dpdk-dev] [PATCH 2/2] Ensure constness of target pointer type

[Jan Blunck]

This adds a check to ensure that the container_of() macro is not used to
cast away (remove) constness.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
---
 lib/librte_eal/common/include/rte_common.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index c421708..e057f6e 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -348,6 +348,8 @@ rte_bsf32(uint32_t v)
 #ifndef container_of
 #define container_of(ptr, type, member)	__extension__ ({		\
 			const typeof(((type *)0)->member) *_ptr = (ptr); \
+			__attribute__((unused)) type *_target_ptr =	\
+				(type *)(ptr);				\
 			(type *)(((uintptr_t)_ptr) - offsetof(type, member)); \
 		})
 #endif
-- 
2.7.4

Re: [dpdk-dev] [PATCH 1/2] Fix container_of() macro to work with const members

[Jan Blunck]

On Tue, Feb 14, 2017 at 3:36 PM, Jan Blunck <jblunck@infradead.org> wrote:
> This fixes the usage of structure members that are declared const to get
> a pointer to the embedding parent structure.

Ping. Is anyone willing to review this?

Thanks,
Jan

>
> Signed-off-by: Jan Blunck <jblunck@infradead.org>
> ---
>  lib/librte_eal/common/include/rte_common.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
> index 8dda3e2..c421708 100644
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -347,8 +347,9 @@ rte_bsf32(uint32_t v)
>   */
>  #ifndef container_of
>  #define container_of(ptr, type, member)        __extension__ ({                \
> -                       typeof(((type *)0)->member) *_ptr = (ptr);      \
> -                       (type *)(((char *)_ptr) - offsetof(type, member)); })
> +                       const typeof(((type *)0)->member) *_ptr = (ptr); \
> +                       (type *)(((uintptr_t)_ptr) - offsetof(type, member)); \
> +               })
>  #endif
>
>  #define _RTE_STR(x) #x
> --
> 2.7.4
>

Re: [dpdk-dev] [PATCH 1/2] Fix container_of() macro to work with const members

[Bruce Richardson]

On Mon, Feb 27, 2017 at 03:28:14PM +0100, Jan Blunck wrote:
> On Tue, Feb 14, 2017 at 3:36 PM, Jan Blunck <jblunck@infradead.org> wrote:
> > This fixes the usage of structure members that are declared const to get
> > a pointer to the embedding parent structure.
> 
> Ping. Is anyone willing to review this?
>
Looks ok to me.

Acked-by: Bruce Richardson <bruce.richardson@intel.com>

Re: [dpdk-dev] [PATCH 1/2] Fix container_of() macro to work with const members

[Thomas Monjalon]

2017-02-27 15:14, Bruce Richardson:
> On Mon, Feb 27, 2017 at 03:28:14PM +0100, Jan Blunck wrote:
> > On Tue, Feb 14, 2017 at 3:36 PM, Jan Blunck <jblunck@infradead.org> wrote:
> > > This fixes the usage of structure members that are declared const to get
> > > a pointer to the embedding parent structure.
> > 
> > Ping. Is anyone willing to review this?
> >
> Looks ok to me.
> 
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>

Applied, thanks