Re: [PATCH bpf-next v2 6/9] bpf: iterators: install libbpf headers when building

On Sat, 2 Oct 2021 at 21:27, Quentin Monnet [off-list ref] wrote:

On Sat, 2 Oct 2021 at 00:20, Andrii Nakryiko [off-list ref] wrote:

quoted

On Fri, Oct 1, 2021 at 4:09 AM Quentin Monnet [off-list ref] wrote:

quoted

API headers from libbpf should not be accessed directly from the
library's source directory. Instead, they should be exported with "make
install_headers". Let's make sure that bpf/preload/iterators/Makefile
installs the headers properly when building.

quoted

quoted

-$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(OUTPUT)
+$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile)            \
+          | $(LIBBPF_OUTPUT) $(LIBBPF_INCLUDE)

Would it make sense for libbpf's Makefile to create include and output
directories on its own? We wouldn't need to have these order-only
dependencies everywhere, right?

Good point, I'll have a look at it.
Quentin

So libbpf already creates the include (and parent $(DESTDIR))
directory, so I can get rid of the related dependencies. But I don't
see an easy solution for the output directory for the object files.
The issue is that libbpf's Makefile includes
tools/scripts/Makefile.include, which checks $(OUTPUT) and errors out
if the directory does not exist. This prevents us from creating the
directory as part of the regular targets. We could create it
unconditionally before running any target, but it's ugly; and I don't
see any simple workaround.

So I'll remove the deps on $(LIBBPF_INCLUDE) and keep the ones on
$(LIBBPF_OUTPUT).