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From: Gavin Hu <gavin.hu@arm.com>
To: dev@dpdk.org
Cc: nd@arm.com, thomas@monjalon.net, david.marchand@redhat.com,
	jerinj@marvell.com, Honnappa.Nagarahalli@arm.com,
	ruifeng.wang@arm.com, phil.yang@arm.com, stable@dpdk.org
Subject: [dpdk-stable] [PATCH v1] mbuf: replace zero-length marker with unnamed union
Date: Tue,  3 Mar 2020 16:27:28 +0000
Message-ID: <20200303162728.93744-1-gavin.hu@arm.com> (raw)

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: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@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. */
 
-- 
2.25.0


             reply	other threads:[~2020-03-03 16:27 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-03 16:27 Gavin Hu [this message]
2020-03-04 12:32 ` [dpdk-stable] [dpdk-dev] " Kevin Traynor
2020-03-07 14:52   ` Gavin Hu
2020-03-07 15:56 ` [dpdk-stable] [PATCH v2] " Gavin Hu
2020-03-09  8:55   ` [dpdk-stable] [dpdk-dev] " Ferruh Yigit
2020-03-09  9:45     ` Gavin Hu
2020-03-09 11:29       ` Ferruh Yigit
2020-03-09 13:30         ` Morten Brørup
2020-03-09 14:16           ` Richardson, Bruce
2020-03-09 14:50             ` [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length markerwith " Morten Brørup
2020-03-11  7:50           ` [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with " Gavin Hu
2020-03-11  9:04             ` Morten Brørup
2020-03-11 12:07               ` Bruce Richardson
2020-03-13  7:36                 ` Gavin Hu
2020-03-13  9:22                 ` Gavin Hu
2020-04-07 17:13                   ` Kevin Traynor
2020-04-08 15:04                     ` Gavin Hu
2020-04-08 15:22                       ` David Marchand
2020-04-09  9:48                         ` Gavin Hu
2020-04-09 10:49                           ` Thomas Monjalon
2020-04-09 16:09                             ` Ray Kinsella
2020-04-11  2:50                             ` Gavin Hu
2020-05-14 13:24                         ` Kevin Traynor
2020-03-09 15:47     ` Stephen Hemminger

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