fix compiling warnings with GCC

GCC 7 plus Ubuntu-16.04 default ccache 3.2.4 reports warnings on switch case fall-through code,
which is commonly seen in DPDK code, which will cause image building failure finally.
It requires newer ccache version to support -Wimplicit-fallthrough.
To suppress the warning, if GCC is version 7 or higher, and it's old ccache version,
will disable the fall-through check.

dpdk-18.05/drivers/net/ark/ark_ethdev_rx.h:39:0,
                  from dpdk-18.05/drivers/net/ark/ark_ethdev_rx.c:36:
dpdk-18.05/arm64-armv8a-linuxapp-gcc/include/rte_mbuf.h: In function ‘rte_pktmbuf_alloc_bulk’:
dpdk-18.05/arm64-armv8a-linuxapp-gcc/include/rte_mbuf.h:1292:7: error: this statement may fall through [-Werror=implicit-fallthrough=]
     idx++;
     ~~~^~

Change-Id: I4d12492471fadef9d349ba9e853a6799512f76f5
Signed-off-by: Lijian Zhang <Lijian.Zhang@arm.com>

diff --git a/dpdk/Makefile b/dpdk/Makefile
index 053fe76..a1e2cb0 100644 (file)
--- a/dpdk/Makefile
+++ b/dpdk/Makefile
@@ -164,6 +164,21 @@ else
 DPDK_EXTRA_CFLAGS := -g -O0
 endif
 
+# -Wimplicit-fallthrough was introduced starting from GCC 7,
+# and it requires newer version of ccache.
+# Disable fallthrough warning for old ccache version.
+ifeq ($(DPDK_CC),gcc)
+GCC_VER_V = "7.0.0"
+CCACHE_VER_V = "3.4.1"
+GCC_VER = $(shell gcc --version | grep ^gcc | sed 's/^.* //g')
+CCACHE_VER = $(shell ccache --version | grep ^ccache | sed 's/^.* //g')
+ifeq ($(shell expr "$(GCC_VER)" ">=" "$(GCC_VER_V)"),1)
+ifeq ($(shell expr "$(CCACHE_VER)" "<" "$(CCACHE_VER_V)"),1)
+DPDK_EXTRA_CFLAGS += -Wimplicit-fallthrough=0
+endif
+endif
+endif
+
 ifeq ($(AESNI),y)
 IPSEC_MB_BUILD_PATH := $(B)/intel-ipsec-mb-$(IPSEC_MB_VER)
 DPDK_EXTRA_CFLAGS += -L$(IPSEC_MB_BUILD_PATH) -I$(IPSEC_MB_BUILD_PATH)