[PATCH 6/6] selftests/bpf: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

urandom_read is built with clang.  Introduce URANDOM_READ_CFLAGS to copy
the compiler flags without appending EXTRA_CFLAGS, which may contain
incompatible options with clang.

Since lib.mk appends options to CFLAGS, ensure that CFLAGS is inherited
after including lib.mk.

Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
---
 tools/testing/selftests/bpf/Makefile | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f75c4f52c02842541f385bc8cbaeab32d8195ed3..50bcf4c386ba52e6cceef4c15f999d9eec6efd6e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -158,6 +158,12 @@ endef
 
 include ../lib.mk
 
+# urandom_read is built with clang. Copy $(CFLAGS) before EXTRA_CFLAGS are
+# appended so that it does not inherit potentially incompatible options.
+URANDOM_READ_CFLAGS := $(CFLAGS)
+
+CFLAGS += $(EXTRA_CFLAGS)
+
 NON_CHECK_FEAT_TARGETS := clean docs-clean
 CHECK_FEAT := $(filter-out $(NON_CHECK_FEAT_TARGETS),$(or $(MAKECMDGOALS), "none"))
 ifneq ($(CHECK_FEAT),)
@@ -255,7 +261,7 @@ endif
 $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom_read.map
 	$(call msg,LIB,,$@)
 	$(Q)$(CLANG) $(CLANG_TARGET_ARCH) \
-		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) \
+		     $(filter-out -static,$(URANDOM_READ_CFLAGS) $(LDFLAGS)) \
 		     $(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
 		     -Wno-unused-command-line-argument \
 		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
@@ -265,7 +271,7 @@ $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom
 $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_read.so
 	$(call msg,BINARY,,$@)
 	$(Q)$(CLANG) $(CLANG_TARGET_ARCH) \
-		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
+		     $(filter-out -static,$(URANDOM_READ_CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
 		     -Wno-unused-command-line-argument \
 		     -lurandom_read $(filter-out -static,$(LDLIBS)) -L$(OUTPUT) \
 		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \

-- 
2.34.1