> Subject: [PATCH v6 05/39] ring: use C11 alignas
>
> The current location used for __rte_aligned(a) for alignment of types
> and variables is not compatible with MSVC. There is only a single
> location accepted by both toolchains.
>
> For variables standard C11 offers alignas(a) supported by conformant
> compilers i.e. both MSVC and GCC.
>
> For types the standard offers no alignment facility that compatibly
> interoperates with C and C++ but may be achieved by relocating the
> placement of __rte_aligned(a) to the aforementioned location accepted
> by all currently supported toolchains.
>
> To allow alignment for both compilers do the following:
>
> * Move __rte_aligned from the end of {struct,union} definitions to
> be between {struct,union} and tag.
>
> The placement between {struct,union} and the tag allows the desired
> alignment to be imparted on the type regardless of the toolchain being
> used for all of GCC, LLVM, MSVC compilers building both C and C++.
>
> * Replace use of __rte_aligned(a) on variables/fields with alignas(a).
>
> Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com>
> Acked-by: Morten Brørup <m...@smartsharesystems.com>
> ---
> lib/ring/rte_ring_core.h | 16 +++++++++-------
> lib/ring/rte_ring_peek_zc.h | 4 ++--
> 2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/lib/ring/rte_ring_core.h b/lib/ring/rte_ring_core.h
> index b770873..f958064 100644
> --- a/lib/ring/rte_ring_core.h
> +++ b/lib/ring/rte_ring_core.h
> @@ -19,6 +19,8 @@
> * instead.
> */
>
> +#include <stdalign.h>
> +
> #ifdef __cplusplus
> extern "C" {
> #endif
> @@ -78,7 +80,7 @@ struct rte_ring_headtail {
>
> union __rte_ring_rts_poscnt {
> /** raw 8B value to read/write *cnt* and *pos* as one atomic op */
> - RTE_ATOMIC(uint64_t) raw __rte_aligned(8);
> + alignas(sizeof(uint64_t)) RTE_ATOMIC(uint64_t) raw;
> struct {
> uint32_t cnt; /**< head/tail reference counter */
> uint32_t pos; /**< head/tail position */
> @@ -94,7 +96,7 @@ struct rte_ring_rts_headtail {
>
> union __rte_ring_hts_pos {
> /** raw 8B value to read/write *head* and *tail* as one atomic op */
> - RTE_ATOMIC(uint64_t) raw __rte_aligned(8);
> + alignas(sizeof(uint64_t)) RTE_ATOMIC(uint64_t) raw;
> struct {
> RTE_ATOMIC(uint32_t) head; /**< head position */
> RTE_ATOMIC(uint32_t) tail; /**< tail position */
> @@ -117,7 +119,7 @@ struct rte_ring_hts_headtail {
> * a problem.
> */
> struct rte_ring {
> - char name[RTE_RING_NAMESIZE] __rte_cache_aligned;
> + alignas(RTE_CACHE_LINE_SIZE) char name[RTE_RING_NAMESIZE];
> /**< Name of the ring. */
> int flags; /**< Flags supplied at creation. */
> const struct rte_memzone *memzone;
> @@ -129,20 +131,20 @@ struct rte_ring {
> RTE_CACHE_GUARD;
>
> /** Ring producer status. */
> - union {
> + union __rte_cache_aligned {
> struct rte_ring_headtail prod;
> struct rte_ring_hts_headtail hts_prod;
> struct rte_ring_rts_headtail rts_prod;
> - } __rte_cache_aligned;
> + };
>
> RTE_CACHE_GUARD;
>
> /** Ring consumer status. */
> - union {
> + union __rte_cache_aligned {
> struct rte_ring_headtail cons;
> struct rte_ring_hts_headtail hts_cons;
> struct rte_ring_rts_headtail rts_cons;
> - } __rte_cache_aligned;
> + };
>
> RTE_CACHE_GUARD;
> };
> diff --git a/lib/ring/rte_ring_peek_zc.h b/lib/ring/rte_ring_peek_zc.h
> index 8fb279c..0b5e34b 100644
> --- a/lib/ring/rte_ring_peek_zc.h
> +++ b/lib/ring/rte_ring_peek_zc.h
> @@ -79,7 +79,7 @@
> * This structure contains the pointers and length of the space
> * reserved on the ring storage.
> */
> -struct rte_ring_zc_data {
> +struct __rte_cache_aligned rte_ring_zc_data {
> /* Pointer to the first space in the ring */
> void *ptr1;
> /* Pointer to the second space in the ring if there is wrap-around.
> @@ -92,7 +92,7 @@ struct rte_ring_zc_data {
> * will give the number of elements available at ptr2.
> */
> unsigned int n1;
> -} __rte_cache_aligned;
> +};
>
> static __rte_always_inline void
> __rte_ring_get_elem_addr(struct rte_ring *r, uint32_t head,
> --
Acked-by: Konstantin Ananyev <konstantin.anan...@huawei.com>
> 1.8.3.1
