Commit 0513eeee authored by Viktor Malik's avatar Viktor Malik Committed by Andrii Nakryiko
Browse files

bpftool: Prevent setting duplicate _GNU_SOURCE in Makefile 



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: default avatarViktor Malik <vmalik@redhat.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarQuentin Monnet <qmo@kernel.org>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/acec3108b62d4df1436cda777e58e93e033ac7a7.1730449390.git.vmalik@redhat.com
parent 4d99e509

tools/bpf/bpftool/Makefile

+5 −1
Original line number Diff line number Diff line
@@ -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))