When building selftests with CFLAGS set via env variable, the value of
CFLAGS is propagated into bpftool Makefile (called from selftests
Makefile). This makes the compilation fail as _GNU_SOURCE is defined two
times - once from selftests Makefile (by including lib.mk) and once from
bpftool Makefile (by calling `llvm-config --cflags`):
$ CFLAGS="" make -C tools/testing/selftests/bpf
[...]
CC /bpf-next/tools/testing/selftests/bpf/tools/build/bpftool/btf.o
<command-line>: error: "_GNU_SOURCE" redefined [-Werror]
<command-line>: note: this is the location of the previous definition
cc1: all warnings being treated as errors
[...]
Filter out -D_GNU_SOURCE from the result of `llvm-config --cflags` in
bpftool Makefile to prevent this error.
Signed-off-by: Viktor Malik <vmalik@xxxxxxxxxx>
Acked-by: Quentin Monnet <qmo@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
tools/bpf/bpftool/Makefile | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index ba927379eb20..a4263dfb5e03 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -147,7 +147,11 @@ ifeq ($(feature-llvm),1)
# If LLVM is available, use it for JIT disassembly
CFLAGS += -DHAVE_LLVM_SUPPORT
LLVM_CONFIG_LIB_COMPONENTS := mcdisassembler all-targets
- CFLAGS += $(shell $(LLVM_CONFIG) --cflags)
+ # llvm-config always adds -D_GNU_SOURCE, however, it may already be in CFLAGS
+ # (e.g. when bpftool build is called from selftests build as selftests
+ # Makefile includes lib.mk which sets -D_GNU_SOURCE) which would cause
+ # compilation error due to redefinition. Let's filter it out here.
+ CFLAGS += $(filter-out -D_GNU_SOURCE,$(shell $(LLVM_CONFIG) --cflags))
LIBS += $(shell $(LLVM_CONFIG) --libs $(LLVM_CONFIG_LIB_COMPONENTS))
ifeq ($(shell $(LLVM_CONFIG) --shared-mode),static)
LIBS += $(shell $(LLVM_CONFIG) --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
--
2.47.0
