[PATCH v3 06/11] selftests/bpf: Tolerate test file compilation failures

[Ricardo B. Marlière]

Individual test files may fail to compile when headers or kernel features
required by that test are absent. Currently this aborts the entire build.

Make the per-test compilation non-fatal: remove the output object on
failure and print a SKIP-TEST marker to stderr. Guard the BTFIDS
post-processing step so it is skipped when the object file is absent.
The linker step will later ignore absent objects, allowing the remaining
tests to build and run.

Use plain printf and $(Q) instead of $(call msg,...) in the BTFIDS block:
the msg macro expands to @printf which is a make-recipe construct and is
invalid as a shell command inside an if-then-fi body; $(Q) restores
echo suppression at the recipe level where it is meaningful.

Signed-off-by: Ricardo B. Marlière <rbm@xxxxxxxx>
---
 tools/testing/selftests/bpf/Makefile | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f4d6c5ed7b3a..e8e92ba9d5b4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -684,11 +684,14 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
 		      $(TRUNNER_TESTS_DIR)/%.c				\
 		      | $(TRUNNER_OUTPUT)/%.test.d
 	$$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
-	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -MMD -MT $$@ -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
+	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -MMD -MT $$@ -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F) || \
+		($(RM) $$(@F); printf '  %-12s %s\n' 'SKIP-TEST' '$$(notdir $$@)' 1>&2)
 	$$(if $$(TEST_NEEDS_BTFIDS),						\
-		$$(call msg,BTFIDS,$(TRUNNER_BINARY),$$@)			\
+		$(Q)if [ -f $$@ ]; then						\
+		printf '  %-8s%s %s\n' "BTFIDS" " [$(TRUNNER_BINARY)]" "$$(notdir $$@)"; \
 		$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@;	\
-		$(RESOLVE_BTFIDS) --patch_btfids $$@.BTF_ids $$@)
+		$(RESOLVE_BTFIDS) --patch_btfids $$@.BTF_ids $$@;		\
+		fi)
 
 $(TRUNNER_TEST_OBJS:.o=.d): $(TRUNNER_OUTPUT)/%.test.d:			\
 			    $(TRUNNER_TESTS_DIR)/%.c			\

-- 
2.53.0