On Tue, Nov 10, 2020 at 08:57:51PM -0800, Andrii Nakryiko wrote: > On Tue, Nov 10, 2020 at 8:46 AM Jean-Philippe Brucker > <jean-philippe@xxxxxxxxxx> wrote: > > > > Cleaning a partial build can fail if the output directory for libbpf > > wasn't created: > > > > $ make -C tools/bpf/bpftool O=/tmp/bpf clean > > /bin/sh: line 0: cd: /tmp/bpf/libbpf/: No such file or directory > > tools/scripts/Makefile.include:17: *** output directory "/tmp/bpf/libbpf/" does not exist. Stop. > > make: *** [Makefile:36: /tmp/bpf/libbpf/libbpf.a-clean] Error 2 > > > > As a result make never gets around to clearing the leftover objects. Add > > the libbpf output directory as clean dependency to ensure clean always > > succeeds (similarly to the "descend" macro). The directory is later > > removed by the clean recipe. > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> > > --- > > tools/bpf/bpftool/Makefile | 8 +++++--- > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > > index f60e6ad3a1df..1358c093b812 100644 > > --- a/tools/bpf/bpftool/Makefile > > +++ b/tools/bpf/bpftool/Makefile > > @@ -27,11 +27,13 @@ LIBBPF = $(LIBBPF_PATH)libbpf.a > > > > BPFTOOL_VERSION ?= $(shell make -rR --no-print-directory -sC ../../.. kernelversion) > > > > -$(LIBBPF): FORCE > > - $(if $(LIBBPF_OUTPUT),@mkdir -p $(LIBBPF_OUTPUT)) > > +$(LIBBPF_OUTPUT): > > + $(QUIET_MKDIR)mkdir -p $@ > > + > > +$(LIBBPF): FORCE | $(LIBBPF_OUTPUT) > > $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) $(LIBBPF_OUTPUT)libbpf.a > > > > -$(LIBBPF)-clean: > > +$(LIBBPF)-clean: $(LIBBPF_OUTPUT) > > shouldn't this be `| $(LIBBPF_OUTPUT)` ? It wouldn't have any effect here. Order-only prerequisites tell make to only build the prerequisite before the target, but not to update the target if the prerequisite was updated. Because $(LIBBPF)-clean is not a file, the recipe is always run and adding the | doesn't make a difference. Thanks, Jean
