[dpdk-dev] [PATCH v10 1/6] mk: fix makefile based cross build errors

[Gavin Hu <gavin.hu@arm.com>]

From: gavin hu <gavin.hu@arm.com>

The "-Wimplicit-fallthrough=2" option was introduced into gcc 7.0, it was
enabled when the cross compiler gcc is greater than 7.0, but for the host
side buildtools/pmdinfogen, if the native gcc is older than 7.0, or the
host cc compiler is clang, it should not be enabled.

The fix is to differentiate the host gcc Werror options from the cross gcc.

gcc -Wp,-MD,./.pmdinfogen.o.d.tmp  -W -Wall -Wstrict-prototypes
-Wmissing-prototypes -Wmissing-declarations -Wold-style-definition
-Wpointer-arith -Wcast-align -Wnested-externs -Wcast-qual
-Wformat-nonliteral -Wformat-security -Wundef -Wwrite-strings -Wdeprecated
-Werror -Wimplicit-fallthrough=2 -Dbbb -Wno-format-truncation -g
-I/home/gavin/arm_repo/dpdk/build/include    -o pmdinfogen.o -c
~/dpdk/buildtools/pmdinfogen/pmdinfogen.c gcc: error:
unrecognized command line option ‘-Wimplicit-fallthrough=2’
~/dpdk/mk/internal/rte.compile-pre.mk:114: recipe for target 'pmdinfogen.o'
failed make[3]: *** [pmdinfogen.o] Error 1

Fixes: ced3e6f8 ("mk: adjust gcc flags for new gcc 7 warnings")
Cc: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Reviewed-by: Steve Capper <Steve.Capper@arm.com>
---
 buildtools/pmdinfogen/Makefile           | 2 +-
 mk/toolchain/gcc/rte.toolchain-compat.mk | 5 +++++
 mk/toolchain/gcc/rte.vars.mk             | 9 +++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/buildtools/pmdinfogen/Makefile b/buildtools/pmdinfogen/Makefile
index bf07b6f2e..ff7a5fae6 100644
--- a/buildtools/pmdinfogen/Makefile
+++ b/buildtools/pmdinfogen/Makefile
@@ -41,7 +41,7 @@ HOSTAPP = dpdk-pmdinfogen
 #
 SRCS-y += pmdinfogen.c
 
-HOST_CFLAGS += $(WERROR_FLAGS) -g
+HOST_CFLAGS += $(HOST_WERROR_FLAGS) -g
 HOST_CFLAGS += -I$(RTE_OUTPUT)/include
 
 include $(RTE_SDK)/mk/rte.hostapp.mk
diff --git a/mk/toolchain/gcc/rte.toolchain-compat.mk b/mk/toolchain/gcc/rte.toolchain-compat.mk
index 255c89677..1e4434fa9 100644
--- a/mk/toolchain/gcc/rte.toolchain-compat.mk
+++ b/mk/toolchain/gcc/rte.toolchain-compat.mk
@@ -15,6 +15,11 @@ GCC_MINOR = $(shell echo __GNUC_MINOR__ | $(CC) -E -x c - | tail -n 1)
 GCC_PATCHLEVEL = $(shell echo __GNUC_PATCHLEVEL__ | $(CC) -E -x c - | tail -n 1)
 GCC_VERSION = $(GCC_MAJOR)$(GCC_MINOR)
 
+HOST_GCC_MAJOR = $(shell echo __GNUC__ | $(HOSTCC) -E -x c - | tail -n 1)
+HOST_GCC_MINOR = $(shell echo __GNUC_MINOR__ | $(HOSTCC) -E -x c - | tail -n 1)
+HOST_GCC_PATCHLEVEL = $(shell echo __GNUC_PATCHLEVEL__ | $(HOSTCC) -E -x c - | tail -n 1)
+HOST_GCC_VERSION = $(HOST_GCC_MAJOR)$(HOST_GCC_MINOR)
+
 # if GCC is older than 4.x
 ifeq ($(shell test $(GCC_VERSION) -lt 40 && echo 1), 1)
 	MACHINE_CFLAGS =
diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
index 7e4531bab..d8b99faf6 100644
--- a/mk/toolchain/gcc/rte.vars.mk
+++ b/mk/toolchain/gcc/rte.vars.mk
@@ -71,6 +71,15 @@ ifeq ($(shell test $(GCC_VERSION) -lt 47 && echo 1), 1)
 WERROR_FLAGS += -Wno-uninitialized
 endif
 
+HOST_WERROR_FLAGS := $(WERROR_FLAGS)
+
+ifeq ($(shell test $(HOST_GCC_VERSION) -gt 70 && echo 1), 1)
+# Tell GCC only to error for switch fallthroughs without a suitable comment
+HOST_WERROR_FLAGS += -Wimplicit-fallthrough=2
+# Ignore errors for snprintf truncation
+HOST_WERROR_FLAGS += -Wno-format-truncation
+endif
+
 ifeq ($(shell test $(GCC_VERSION) -gt 70 && echo 1), 1)
 # Tell GCC only to error for switch fallthroughs without a suitable comment
 WERROR_FLAGS += -Wimplicit-fallthrough=2
-- 
2.11.0