[dpdk-stable] [PATCH] build: disable gcc 10 zero-length-bounds warning

[Kevin Traynor <ktraynor@redhat.com>]

gcc 10 issues warnings about the use of rearm_data marker
from struct rte_mbuf.

e.g.
../drivers/net/enic/enic_rxtx_vec_avx2.c: In function ‘rx_one’:
../drivers/net/enic/enic_rxtx_vec_avx2.c:21:2:
warning:
array subscript 0 is outside the bounds of an interior zero-length array
‘RTE_MARKER64’ {aka ‘long unsigned int[0]’} [-Wzero-length-bounds]
   21 |  *(uint64_t *)&mb->rearm_data = enic->mbuf_initializer;
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../lib/librte_mbuf/rte_mbuf.h:45,
                 from ../drivers/net/enic/enic_rxtx_vec_avx2.c:6:
../lib/librte_mbuf/rte_mbuf_core.h:484:15:
note: while referencing ‘rearm_data’
  484 |  RTE_MARKER64 rearm_data;
      |

Disable this warning for gcc 10 in order to allow v20.05 to build
without changes to struct rte_mbuf.

Bugzilla ID: 396
Cc: stable@dpdk.org

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>

---
Sending as per discussion at this mornings release meeting:
http://inbox.dpdk.org/dev/2980eb50-124c-9da8-9927-0678081b652b@intel.com/

Reference to Gavin's patch:
http://inbox.dpdk.org/dev/CAJFAV8yL2GvEJtTXOLk6o0eXHi4CpZmqCoRsfN2WcDe_ju1C8A@mail.gmail.com/#t
---
 config/meson.build           | 4 ++++
 mk/toolchain/gcc/rte.vars.mk | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/config/meson.build b/config/meson.build
index a1c38c053..43ab11310 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -209,4 +209,8 @@ warning_flags = [
 	'-Wno-missing-field-initializers'
 ]
+if cc.get_id() == 'gcc' and cc.version().version_compare('>=10.0')
+# FIXME: Bugzilla 396
+	warning_flags += '-Wno-zero-length-bounds'
+endif
 if not dpdk_conf.get('RTE_ARCH_64')
 # for 32-bit, don't warn about casting a 32-bit pointer to 64-bit int - it's fine!!
diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
index f19305e49..928f0e083 100644
--- a/mk/toolchain/gcc/rte.vars.mk
+++ b/mk/toolchain/gcc/rte.vars.mk
@@ -82,4 +82,9 @@ WERROR_FLAGS += -Wno-uninitialized
 endif
 
+ifeq ($(shell test $(GCC_VERSION) -ge 100 && echo 1), 1)
+# FIXME: Bugzilla 396
+WERROR_FLAGS += -Wno-zero-length-bounds
+endif
+
 HOST_WERROR_FLAGS := $(WERROR_FLAGS)
 
-- 
2.21.3