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[178.94.200.168]) by smtp.gmail.com with ESMTPSA id s7sm959288ljs.16.2019.09.18.04.05.20 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 18 Sep 2019 04:05:20 -0700 (PDT) Date: Wed, 18 Sep 2019 14:05:18 +0300 From: Ivan Khoronzhuk To: Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , Yonghong Song , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , john fastabend , open list , Networking , bpf , clang-built-linux@googlegroups.com, sergei.shtylyov@cogentembedded.com Subject: Re: [PATCH v3 bpf-next 11/14] libbpf: makefile: add C/CXX/LDFLAGS to libbpf.so and test_libpf targets Message-ID: <20190918110517.GD2908@khorivan> Mail-Followup-To: Andrii Nakryiko , Alexei Starovoitov , Daniel Borkmann , Yonghong Song , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , john fastabend , open list , Networking , bpf , clang-built-linux@googlegroups.com, sergei.shtylyov@cogentembedded.com References: <20190916105433.11404-1-ivan.khoronzhuk@linaro.org> <20190916105433.11404-12-ivan.khoronzhuk@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Sep 17, 2019 at 10:19:22PM -0700, Andrii Nakryiko wrote: >On Mon, Sep 16, 2019 at 4:00 AM Ivan Khoronzhuk > wrote: >> >> In case of LDFLAGS and EXTRA_CC/CXX flags there is no way to pass them >> correctly to build command, for instance when --sysroot is used or >> external libraries are used, like -lelf, wich can be absent in >> toolchain. This can be used for samples/bpf cross-compiling allowing >> to get elf lib from sysroot. >> >> Signed-off-by: Ivan Khoronzhuk >> --- >> tools/lib/bpf/Makefile | 11 ++++++++--- >> 1 file changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile >> index c6f94cffe06e..bccfa556ef4e 100644 >> --- a/tools/lib/bpf/Makefile >> +++ b/tools/lib/bpf/Makefile >> @@ -94,6 +94,10 @@ else >> CFLAGS := -g -Wall >> endif >> >> +ifdef EXTRA_CXXFLAGS >> + CXXFLAGS := $(EXTRA_CXXFLAGS) >> +endif >> + >> ifeq ($(feature-libelf-mmap), 1) >> override CFLAGS += -DHAVE_LIBELF_MMAP_SUPPORT >> endif >> @@ -176,8 +180,9 @@ $(BPF_IN): force elfdep bpfdep >> $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION) >> >> $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN) >> - $(QUIET_LINK)$(CC) --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \ >> - -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@ >> + $(QUIET_LINK)$(CC) $(LDFLAGS) \ >> + --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \ >> + -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@ >> @ln -sf $(@F) $(OUTPUT)libbpf.so >> @ln -sf $(@F) $(OUTPUT)libbpf.so.$(LIBBPF_MAJOR_VERSION) >> >> @@ -185,7 +190,7 @@ $(OUTPUT)libbpf.a: $(BPF_IN) >> $(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^ >> >> $(OUTPUT)test_libbpf: test_libbpf.cpp $(OUTPUT)libbpf.a >> - $(QUIET_LINK)$(CXX) $(INCLUDES) $^ -lelf -o $@ >> + $(QUIET_LINK)$(CXX) $(CXXFLAGS) $(LDFLAGS) $(INCLUDES) $^ -lelf -o $@ > >Instead of doing ifdef EXTRA_CXXFLAGS bit above, you can just include >both $(CXXFLAGS) and $(EXTRA_CXXFLAGS), which will do the right thing >(and is actually recommended my make documentation way to do this). It's good practice to follow existent style, I've done similar way as for CFLAGS + EXTRACFLAGS here, didn't want to verify it can impact on smth else. And my goal is not to correct everything but embed my functionality, series tool large w/o it. > >But actually, there is no need to use C++ compiler here, >test_libbpf.cpp can just be plain C. Do you mind renaming it to .c and >using C compiler instead? Seems like, will try in next v. > >> >> $(OUTPUT)libbpf.pc: >> $(QUIET_GEN)sed -e "s|@PREFIX@|$(prefix)|" \ >> -- >> 2.17.1 >> -- Regards, Ivan Khoronzhuk