[PATCH 01/13] Makefile: Use make variables for static checker configuration

[David Gibson <david@gibson.dropbear.id.au>]

Our cppcheck and clang-tidy rules don't really follow normal Makefile
conventions.  Usually any commands other than the very basics have their
binary specified in a variable so it can be overridden on the command line
if they're in an unusual location.  Implement that for $(CPPCHECK) and
$(CLANG_TIDY)

Likewise flags to tools usually have their own Make variable.  Do the same
with $(CLANG_TIDY_FLAGS) and $(CPPCHECK_FLAGS).  Note that these only have
the options specifically for the static checker, not compiler flags which
we are also supplying to the static checker - those are derived from
FLAGS / CFLAGS / CPPFLAGS as before.

As part of that we change the probing for --check-level=exhaustive from
being run as part of the cppcheck target, to being run when we build the
CPPCHECK_FLAGS variable.  That doesn't make any real difference now, but
will make things nicer if we need multiple cppcheck targets in future (e.g.
for passt-repair).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 Makefile | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index f697c12b..17e70d22 100644
--- a/Makefile
+++ b/Makefile
@@ -174,21 +174,27 @@ docs: README.md
 		done < README.md;					\
 	) > README.plain.md
 
+CLANG_TIDY = clang-tidy
+CLANG_TIDY_FLAGS = -DCLANG_TIDY_58992
+
 clang-tidy: $(PASST_SRCS)
-	clang-tidy $^ -- $(filter-out -pie,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) \
-	           -DCLANG_TIDY_58992
+	$(CLANG_TIDY) $^ -- $(filter-out -pie,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) \
+		$(CLANG_TIDY_FLAGS)
 
-cppcheck: $(PASST_SRCS) $(HEADERS)
-	if cppcheck --check-level=exhaustive /dev/null > /dev/null 2>&1; then \
-		CPPCHECK_EXHAUSTIVE="--check-level=exhaustive";		\
-	else								\
-		CPPCHECK_EXHAUSTIVE=;					\
-	fi;								\
-	cppcheck --std=c11 --error-exitcode=1 --enable=all --force	\
+CPPCHECK = cppcheck
+CPPCHECK_FLAGS = --std=c11 --error-exitcode=1 --enable=all --force	\
 	--inconclusive --library=posix --quiet				\
-	$${CPPCHECK_EXHAUSTIVE}						\
 	--inline-suppr							\
-	--suppress=missingIncludeSystem \
+	$(shell if $(CPPCHECK) --quiet --check-level=exhaustive /dev/null; then \
+		echo "--check-level=exhaustive";			\
+	else								\
+		echo "";						\
+	fi)								\
+	--suppress=missingIncludeSystem					\
 	--suppress=unusedStructMember					\
-	$(filter -D%,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) -D CPPCHECK_6936	\
-	$^
+	 -D CPPCHECK_6936
+
+cppcheck: $(PASST_SRCS) $(HEADERS)
+	$(CPPCHECK) $(CPPCHECK_FLAGS) 					\
+		$(filter -D%,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) $^		\
+		$^
-- 
2.53.0