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Tue, 04 Aug 2026 10:02:19 -0700 (PDT) Received: from powertower.localdomain ([64.180.35.234]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84f2e4d3926sm55508b3a.28.2026.08.04.10.02.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2026 10:02:18 -0700 (PDT) From: Mykola Lysenko To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, memxor@gmail.com, nickolay.lysenko@gmail.com Subject: [RFC PATCH bpf-next v5 1/8] selftests/bpf: keep headers off the generic link command line Date: Tue, 4 Aug 2026 10:01:49 -0700 Message-ID: <20260804170156.1709916-2-nickolay.lysenko@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260804170156.1709916-1-nickolay.lysenko@gmail.com> References: <20260804170156.1709916-1-nickolay.lysenko@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The generic '$(OUTPUT)/%:%.c' rule links with '$(LINK.c) $^', so every prerequisite of such a binary lands on the compiler driver's command line. That only works while none of them is a header: gcc tolerates a stray .h argument on a link line, but clang treats it as a request to precompile the header and fails with "cannot specify -o when generating multiple output files". Filter headers out of the recipe, with a comment: header prerequisites on these targets are useful for dependency tracking - the next patch declares one - and the constraint is easy to rediscover the hard way. Signed-off-by: Mykola Lysenko --- tools/testing/selftests/bpf/Makefile | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 55d394438..65c702613 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -258,9 +258,12 @@ $(OUTPUT)/%.o: %.c $(call msg,CC,,$@) $(Q)$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@ +# Headers may appear among the prerequisites for dependency tracking; +# they must not reach the clang/gcc command line (clang treats a bare .h +# argument as a precompiled-header job and refuses -o). $(OUTPUT)/%:%.c $(call msg,BINARY,,$@) - $(Q)$(LINK.c) $^ $(LDLIBS) -o $@ + $(Q)$(LINK.c) $(filter-out %.h,$^) $(LDLIBS) -o $@ # LLVM's ld.lld doesn't support all the architectures, so use it only on x86 ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 riscv)) -- 2.43.0