Subject: Re: [PATCH bpf-next 1/9] selftests/bpf: prevent headers to be compiled as C code

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 26 Jul 2019 14:21:52 -0700

On 07/26, Andrii Nakryiko wrote:
> Apprently listing header as a normal dependency for a binary output
> makes it go through compilation as if it was C code. This currently
> works without a problem, but in subsequent commits causes problems for
> differently generated test.h for test_progs. Marking those headers as
> order-only dependency solves the issue.
Are you sure it will not result in a situation where
test_progs/test_maps is not regenerated if tests.h is updated.

If I read the following doc correctly, order deps make sense for
directories only:
https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html

Can you maybe double check it with:
* make
* add new prog_tests/test_something.c
* make
to see if the binary is regenerated with test_something.c?

Maybe fix the problem of header compilation by having '#ifndef
DECLARE_TEST #define DECLARE_TEST() #endif' in tests.h instead?

> Signed-off-by: Andrii Nakryiko <[email-masked]>
> ---
>  tools/testing/selftests/bpf/Makefile | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 11c9c62c3362..bb66cc4a7f34 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -235,7 +235,7 @@ PROG_TESTS_H := $(PROG_TESTS_DIR)/tests.h
>  PROG_TESTS_FILES := $(wildcard prog_tests/*.c)
>  test_progs.c: $(PROG_TESTS_H)
>  $(OUTPUT)/test_progs: CFLAGS += $(TEST_PROGS_CFLAGS)
> -$(OUTPUT)/test_progs: test_progs.c $(PROG_TESTS_H) $(PROG_TESTS_FILES)
> +$(OUTPUT)/test_progs: test_progs.c $(PROG_TESTS_FILES) | $(PROG_TESTS_H)
>  $(PROG_TESTS_H): $(PROG_TESTS_FILES) | $(PROG_TESTS_DIR)
>  	$(shell ( cd prog_tests/; \
>  		  echo '/* Generated header, do not edit */'; \
> @@ -256,7 +256,7 @@ MAP_TESTS_H := $(MAP_TESTS_DIR)/tests.h
>  MAP_TESTS_FILES := $(wildcard map_tests/*.c)
>  test_maps.c: $(MAP_TESTS_H)
>  $(OUTPUT)/test_maps: CFLAGS += $(TEST_MAPS_CFLAGS)
> -$(OUTPUT)/test_maps: test_maps.c $(MAP_TESTS_H) $(MAP_TESTS_FILES)
> +$(OUTPUT)/test_maps: test_maps.c $(MAP_TESTS_FILES) | $(MAP_TESTS_H)
>  $(MAP_TESTS_H): $(MAP_TESTS_FILES) | $(MAP_TESTS_DIR)
>  	$(shell ( cd map_tests/; \
>  		  echo '/* Generated header, do not edit */'; \
> @@ -277,7 +277,7 @@ VERIFIER_TESTS_H := $(VERIFIER_TESTS_DIR)/tests.h
>  VERIFIER_TEST_FILES := $(wildcard verifier/*.c)
>  test_verifier.c: $(VERIFIER_TESTS_H)
>  $(OUTPUT)/test_verifier: CFLAGS += $(TEST_VERIFIER_CFLAGS)
> -$(OUTPUT)/test_verifier: test_verifier.c $(VERIFIER_TESTS_H)
> +$(OUTPUT)/test_verifier: test_verifier.c | $(VERIFIER_TEST_FILES) $(VERIFIER_TESTS_H)
>  $(VERIFIER_TESTS_H): $(VERIFIER_TEST_FILES) | $(VERIFIER_TESTS_DIR)
>  	$(shell ( cd verifier/; \
>  		  echo '/* Generated header, do not edit */'; \
> -- 
> 2.17.1
>