[PATCH] Makefile: check for cppcheck's --check-level option in cppcheck target

[Stefano Brivio <sbrivio@redhat.com>]

Don't run cppcheck to find out if the --check-level=exhaustive option
is available, unless we're actually going to run cppcheck later.

To avoid this, move this check under the cppcheck target, and
implement it in shell script instead of using Makefile directives,
because we can't easily implement conditionals in recipes.

Reported-by: Rahil Bhimjiani <me@rahil.website>
Link: https://bugs.gentoo.org/920795
Fixes: 8640d62af719 ("cppcheck: Use "exhaustive" level checking when available")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 Makefile | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index af4fa87..75d0bf3 100644
--- a/Makefile
+++ b/Makefile
@@ -287,17 +287,17 @@ clang-tidy: $(SRCS) $(HEADERS)
 	-config='{CheckOptions: [{key: bugprone-suspicious-string-compare.WarnOnImplicitComparison, value: "false"}]}' \
 	--warnings-as-errors=* $(SRCS) -- $(filter-out -pie,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) -DCLANG_TIDY_58992
 
-CPPCHECK_EXHAUSTIVE :=
-ifeq ($(shell cppcheck --check-level=exhaustive /dev/null > /dev/null 2>&1; echo $$?),0)
-	CPPCHECK_EXHAUSTIVE += --check-level=exhaustive
-endif
-
 SYSTEM_INCLUDES := /usr/include $(wildcard /usr/include/$(TARGET))
 ifeq ($(shell $(CC) -v 2>&1 | grep -c "gcc version"),1)
 VER := $(shell $(CC) -dumpversion)
 SYSTEM_INCLUDES += /usr/lib/gcc/$(TARGET)/$(VER)/include
 endif
 cppcheck: $(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	\
 	--inconclusive --library=posix --quiet				\
 	$(CPPCHECK_EXHAUSTIVE)						\
-- 
@@ -287,17 +287,17 @@ clang-tidy: $(SRCS) $(HEADERS)
 	-config='{CheckOptions: [{key: bugprone-suspicious-string-compare.WarnOnImplicitComparison, value: "false"}]}' \
 	--warnings-as-errors=* $(SRCS) -- $(filter-out -pie,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) -DCLANG_TIDY_58992
 
-CPPCHECK_EXHAUSTIVE :=
-ifeq ($(shell cppcheck --check-level=exhaustive /dev/null > /dev/null 2>&1; echo $$?),0)
-	CPPCHECK_EXHAUSTIVE += --check-level=exhaustive
-endif
-
 SYSTEM_INCLUDES := /usr/include $(wildcard /usr/include/$(TARGET))
 ifeq ($(shell $(CC) -v 2>&1 | grep -c "gcc version"),1)
 VER := $(shell $(CC) -dumpversion)
 SYSTEM_INCLUDES += /usr/lib/gcc/$(TARGET)/$(VER)/include
 endif
 cppcheck: $(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	\
 	--inconclusive --library=posix --quiet				\
 	$(CPPCHECK_EXHAUSTIVE)						\
-- 
2.39.2