On Thu, Oct 7, 2021 at 12:44 PM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: > > The "install_headers" target in libbpf's Makefile would unconditionally > export all API headers to the target directory. When those headers are > installed to compile another application, this means that make always > finds newer dependencies for the source files relying on those headers, > and deduces that the targets should be rebuilt. > > Avoid that by making "install_headers" depend on the source header > files, and (re-)install them only when necessary. > > Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx> > --- > tools/lib/bpf/Makefile | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile > index 41e4f78dbad5..a92d3b9692a8 100644 > --- a/tools/lib/bpf/Makefile > +++ b/tools/lib/bpf/Makefile > @@ -241,15 +241,23 @@ install_lib: all_cmd > $(call do_install_mkdir,$(libdir_SQ)); \ > cp -fpR $(LIB_FILE) $(DESTDIR)$(libdir_SQ) > > -INSTALL_HEADERS = bpf.h libbpf.h btf.h libbpf_common.h libbpf_legacy.h xsk.h \ > - bpf_helpers.h $(BPF_GENERATED) bpf_tracing.h \ > - bpf_endian.h bpf_core_read.h skel_internal.h \ > - libbpf_version.h > +SRC_HDRS := bpf.h libbpf.h btf.h libbpf_common.h libbpf_legacy.h xsk.h \ > + bpf_helpers.h bpf_tracing.h bpf_endian.h bpf_core_read.h \ > + skel_internal.h libbpf_version.h > +GEN_HDRS := $(BPF_GENERATED) > +INSTALL_SRC_HDRS := $(addprefix $(DESTDIR)$(prefix)/include/bpf/,$(SRC_HDRS)) > +INSTALL_GEN_HDRS := $(addprefix $(DESTDIR)$(prefix)/include/bpf/, \ > + $(notdir $(GEN_HDRS))) I've added INSTALL_PFX := $(DESTDIR)$(prefix)/include/bpf and used it where possible > +$(INSTALL_SRC_HDRS): $(DESTDIR)$(prefix)/include/bpf/%.h: %.h > + $(call QUIET_INSTALL, $@) \ > + $(call do_install,$<,$(prefix)/include/bpf,644) > +$(INSTALL_GEN_HDRS): $(DESTDIR)$(prefix)/include/bpf/%.h: $(OUTPUT)%.h > + $(call QUIET_INSTALL, $@) \ > + $(call do_install,$<,$(prefix)/include/bpf,644) > > -install_headers: $(BPF_GENERATED) > - $(call QUIET_INSTALL, headers) \ > - $(foreach hdr,$(INSTALL_HEADERS), \ > - $(call do_install,$(hdr),$(prefix)/include/bpf,644);) > +INSTALL_HEADERS := $(INSTALL_SRC_HDRS) $(INSTALL_GEN_HDRS) I felt like INSTALL_HEADERS just adds one more indirection and otherwise is not useful, so I dropped it and inlined $(INSTALL_SRC_HDRS) $(INSTALL_GEN_HDRS) below > + > +install_headers: $(BPF_GENERATED) $(INSTALL_HEADERS) > > install_pkgconfig: $(PC_FILE) > $(call QUIET_INSTALL, $(PC_FILE)) \ > -- > 2.30.2 >
