Hi Ferruh,
> -----Original Message----- > From: Ferruh Yigit <ferruh.yi...@intel.com> > Sent: Monday, March 9, 2020 4:55 PM > To: Gavin Hu <gavin...@arm.com>; dev@dpdk.org > Cc: nd <n...@arm.com>; david.march...@redhat.com; tho...@monjalon.net; > ktray...@redhat.com; jer...@marvell.com; Honnappa Nagarahalli > <honnappa.nagaraha...@arm.com>; Ruifeng Wang > <ruifeng.w...@arm.com>; Phil Yang <phil.y...@arm.com>; Joyce Kong > <joyce.k...@arm.com>; sta...@dpdk.org; Olivier MATZ > <olivier.m...@6wind.com>; Konstantin Ananyev > <konstantin.anan...@intel.com>; Andrew Rybchenko > <arybche...@solarflare.com> > Subject: Re: [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with > unnamed union > > On 3/7/2020 3:56 PM, Gavin Hu wrote: > > 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> > > --- > > v2: > > * change 'uint64_t rearm_data' to 'uint_64_t rearm_data[1]' to fix > > the SFC PMD compiling error on x86. <Kevin Traynor> > > --- > > 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..34cb152e2 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[1]; > We are using zero length array as markers only and know what we are doing > with them, > what would you think disabling the warning instead of increasing the > complexity > in mbuf struct? Okay, I will add -Wno-zero-length-bounds to the compiler toolchain flags. /Gavin
