When trying to build BPF selftests with additional compiler and linker flags, we're running into multiple problems. This series addresses all of them: - CFLAGS are not passed to sub-makes of bpftool and libbpf. This is a problem when compiling with PIE as libbpf.a ends up being non-PIE and cannot be linked with other binaries (patch #1). - bpftool Makefile runs `llvm-config --cflags` and appends the result to CFLAGS. The result typically contains `-D_GNU_SOURCE` which may be already set in CFLAGS. That causes a compilation error (patch #2). - Some GCC flags are not supported by Clang but there are binaries which are always built with Clang but reuse user-defined CFLAGS. When CFLAGS contain such flags, compilation fails (patch #3). Changelog: ---------- v1 -> v2: - cover forgotten case in patch#1 (noted by Eduard) - remove -D_GNU_SOURCE unconditionally in patch#2 (suggested by Andrii) - rewrite patch#3 to just add -Wno-unused-command-line-argument (suggested by Andrii) Viktor Malik (3): selftests/bpf: Allow building with extra flags bpftool: Prevent setting duplicate _GNU_SOURCE in Makefile selftests/bpf: Disable warnings on unused flags for Clang builds tools/bpf/bpftool/Makefile | 6 +++++- tools/testing/selftests/bpf/Makefile | 28 +++++++++++++++++++--------- 2 files changed, 24 insertions(+), 10 deletions(-) -- 2.47.0
