2026-06-02 15:47 UTC+0100 ~ Leo Yan <[email protected]> > bpftool builds a bootstrap libbpf with HOSTCC, but the libbpf submake can > still inherit target build flags through CFLAGS. This can break cross > builds when host objects are compiled with target-only options. > > Since HOST_CFLAGS contains warning options that are not suitable for > building libbpf, use LIBBPF_BOOTSTRAP_CFLAGS with the warning options > removed to build the bootstrap libbpf. Clear EXTRA_CFLAGS so target > extra flags are not mixed into the host bootstrap libbpf build. > > Signed-off-by: Leo Yan <[email protected]> > --- > 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 > 0febf60e1b64656035dfe93cd15cba090015587a..1f033e578f90a2d6b93168ab41399de758bdf659 > 100644 > --- a/tools/bpf/bpftool/Makefile > +++ b/tools/bpf/bpftool/Makefile > @@ -47,7 +47,8 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: > $(BPF_DIR)/%.h | $(LIBBPF_HDRS_ > $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | > $(LIBBPF_BOOTSTRAP_OUTPUT) > $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \ > DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR:/=) prefix= \ > - ARCH= CROSS_COMPILE= CC="$(HOSTCC)" LD="$(HOSTLD)" > AR="$(HOSTAR)" $@ install_headers > + ARCH= CROSS_COMPILE= CC="$(HOSTCC)" LD="$(HOSTLD)" > AR="$(HOSTAR)" \ > + CFLAGS="$(LIBBPF_BOOTSTRAP_CFLAGS)" EXTRA_CFLAGS= $@ > install_headers > > $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: > $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR) > $(call QUIET_INSTALL, $@) > @@ -92,6 +93,9 @@ HOST_CFLAGS := $(subst > -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\ > $(subst $(CLANG_CROSS_FLAGS),,$(CFLAGS))) > HOST_LDFLAGS := $(LDFLAGS) > > +# Remove warnings for libbpf bootstrap build
Nitpick: We could expand this comment to briefly explain why. Not sure it's worth a respin, though. > +LIBBPF_BOOTSTRAP_CFLAGS := $(filter-out -W -Wall -Wextra -Wformat > -Wformat-signedness,$(HOST_CFLAGS)) Do we need to remove all warnings, or would it be sufficient to take out -Wformat and -Wformat-signedness? I don't mind removing them all if necessary, just asking. Acked-by: Quentin Monnet <[email protected]> Thanks!
