On 03/03/2020 16:27, Gavin Hu wrote:
> gcc 10.0.1 reports: error: array subscript 0 is outside the bounds of an
> interior zero-length array 'RTE_MARKER64' {aka 'long unsigned int[0]'}
> [-Werror=zero-length-bounds] 310 | *(uint64_t *)(&mbuf->rearm_data) =
> val;
>
> Declaring zero-length arrays in other contexts, including as interior
> members of structure objects or as non-member objects, is discouraged.
> Accessing elements of zero-length arrays declared in such contexts is
> undefined and may be diagnosed.[1]
>
> Fix by using unnamed union and struct.
>
> https://bugs.dpdk.org/show_bug.cgi?id=396
>
> Bugzilla ID: 396
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
>
> Fixes: 3e6181b07038 ("mbuf: use structure marker from EAL")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Gavin Hu <gavin...@arm.com>
> ---
> lib/librte_mbuf/rte_mbuf_core.h | 54 +++++++++++++++++++--------------
> 1 file changed, 32 insertions(+), 22 deletions(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
> index b9a59c879..5390ddcfa 100644
> --- a/lib/librte_mbuf/rte_mbuf_core.h
> +++ b/lib/librte_mbuf/rte_mbuf_core.h
> @@ -480,31 +480,41 @@ struct rte_mbuf {
> rte_iova_t buf_physaddr; /**< deprecated */
> } __rte_aligned(sizeof(rte_iova_t));
>
> - /* next 8 bytes are initialised on RX descriptor rearm */
> - RTE_MARKER64 rearm_data;
> - uint16_t data_off;
> -
> - /**
> - * Reference counter. Its size should at least equal to the size
> - * of port field (16 bits), to support zero-copy broadcast.
> - * It should only be accessed using the following functions:
> - * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and
> - * rte_mbuf_refcnt_set(). The functionality of these functions (atomic,
> - * or non-atomic) is controlled by the CONFIG_RTE_MBUF_REFCNT_ATOMIC
> - * config option.
> - */
> RTE_STD_C11
> union {
> - rte_atomic16_t refcnt_atomic; /**< Atomically accessed refcnt */
> - /** Non-atomically accessed refcnt */
> - uint16_t refcnt;
> - };
> - uint16_t nb_segs; /**< Number of segments. */
> + /* next 8 bytes are initialised on RX descriptor rearm */
> + uint64_t rearm_data;
> + RTE_STD_C11
> + struct {
> + uint16_t data_off;
> +
> + /**
> + * Reference counter. Its size should at least equal to
> + * the size of port field (16 bits), to support
> + * zero-copy broadcast. It should only be accessed
> + * using the following functions:
> + * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(),
> + * and rte_mbuf_refcnt_set(). The functionality of
> + * these functions (atomic, or non-atomic) is
> + * controlled by the CONFIG_RTE_MBUF_REFCNT_ATOMIC
> + * config option.
> + */
> + RTE_STD_C11
> + union {
> + /**< Atomically accessed refcnt */
> + rte_atomic16_t refcnt_atomic;
> + /** Non-atomically accessed refcnt */
> + uint16_t refcnt;
> + };
> + uint16_t nb_segs; /**< Number of segments. */
>
> - /** Input port (16 bits to support more than 256 virtual ports).
> - * The event eth Tx adapter uses this field to specify the output port.
> - */
> - uint16_t port;
> + /** Input port (16 bits to support more than 256
> + * virtual ports). The event eth Tx adapter uses this
> + * field to specify the output port.
> + */
> + uint16_t port;
> + };
> + };
>
> uint64_t ol_flags; /**< Offload features. */
>
>
Hi Gavin, this causes some errors on x86:
# gcc --version | head -1
gcc (GCC) 10.0.1 20200216 (Red Hat 10.0.1-0.8)
In file included from
../lib/librte_eal/common/include/arch/x86/rte_byteorder.h:13,
from ../drivers/net/sfc/sfc_ef10_rx.c:14:
../drivers/net/sfc/sfc_ef10_rx.c: In function ‘sfc_ef10_rx_process_event’:
../drivers/net/sfc/sfc_ef10_rx.c:309:39: error: subscripted value is
neither array nor pointer nor vector
309 | RTE_BUILD_BUG_ON(sizeof(m->rearm_data[0]) !=
sizeof(rxq->rearm_data));
| ^
../lib/librte_eal/common/include/rte_common.h:292:65: note: in
definition of macro ‘RTE_BUILD_BUG_ON’
292 | #define RTE_BUILD_BUG_ON(condition) ((void)sizeof(char[1 -
2*!!(condition)]))
|
^~~~~~~~~
../drivers/net/sfc/sfc_ef10_rx.c:310:15: error: subscripted value is
neither array nor pointer nor vector
310 | m->rearm_data[0] = rxq->rearm_data;
|
