From f7ff6597a7534da51c2962691e177c624cb567c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?=
 <avarab@gmail.com>
Date: Tue, 5 Jul 2022 15:46:57 +0200
Subject: [PATCH] cocci: add a "coccicheck-test" target and test *.cocci rules
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Add a "coccicheck-test" target to test our *.cocci rules, and as a
demonstration add tests for the rules added in 39ea59a2570 (remove
unnecessary NULL check before free(3), 2016-10-08) and
1b83d1251ed (coccinelle: add a rule to make "expression" code use
FREE_AND_NULL(), 2017-06-15).

I considered making use of the "spatch --test" option, and the choice
of a "tests" over a "t" directory is to make these tests compatible
with such a future change.

Unfortunately "spatch --test" doesn't return meaningful exit codes,
AFAICT you need to "grep" its output to see if the *.res is what you
expect. There's "--test-okfailed", but I didn't find a way to sensibly
integrate those (it relies on some in-between status files, but
doesn't help with the status codes).

Instead let's use a "--sp-file" pattern similar to the main
"coccicheck" rule, with the difference that we use and compare the
two *.res files with cmp(1).

The --very-quiet and --no-show-diff options ensure that we don't need
to pipe stdout and stderr somewhere. Unlike the "%.cocci.patch" rule
we're not using the diff.

The "cmp || git diff" is optimistically giving us better output on
failure, but even if we only have POSIX cmp and no system git
installed we'll still fail with the "cmp", just with an error message
that isn't as friendly. The "2>/dev/null" is in case we don't have a
"git" installed.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Makefile                          | 19 +++++++++++++++++++
 contrib/coccinelle/tests/free.c   | 11 +++++++++++
 contrib/coccinelle/tests/free.res |  9 +++++++++
 shared.mak                        |  1 +
 4 files changed, 40 insertions(+)
 create mode 100644 contrib/coccinelle/tests/free.c
 create mode 100644 contrib/coccinelle/tests/free.res

diff --git a/Makefile b/Makefile
index 1ccf13595d..c4064f8394 100644
--- a/Makefile
+++ b/Makefile
@@ -3123,6 +3123,8 @@ check: $(GENERATED_H)
 		exit 1; \
 	fi
 
+COCCI_TEST_RES = $(wildcard contrib/coccinelle/tests/*.res)
+
 %.cocci.patch: %.cocci $(COCCI_SOURCES)
 	$(QUIET_SPATCH) \
 	if test $(SPATCH_BATCH_SIZE) = 0; then \
@@ -3143,6 +3145,22 @@ check: $(GENERATED_H)
 	then \
 		echo '    ' SPATCH result: $@; \
 	fi
+
+COCCI_TEST_RES_GEN = $(addprefix .build/,$(COCCI_TEST_RES))
+$(COCCI_TEST_RES_GEN): .build/%.res : %.c
+$(COCCI_TEST_RES_GEN): .build/%.res : %.res
+$(COCCI_TEST_RES_GEN): .build/contrib/coccinelle/tests/%.res : contrib/coccinelle/%.cocci
+	$(call mkdir_p_parent_template)
+	$(QUIET_SPATCH_T)$(SPATCH) $(SPATCH_FLAGS) \
+		--very-quiet --no-show-diff \
+		--sp-file $< -o $@ \
+		$(@:.build/%.res=%.c) && \
+	cmp $(@:.build/%=%) $@ || \
+	git -P diff --no-index $(@:.build/%=%) $@ 2>/dev/null; \
+
+.PHONY: coccicheck-test
+coccicheck-test: $(COCCI_TEST_RES_GEN)
+
 coccicheck: $(addsuffix .patch,$(filter-out %.pending.cocci,$(wildcard contrib/coccinelle/*.cocci)))
 
 # See contrib/coccinelle/README
@@ -3404,6 +3422,7 @@ profile-clean:
 	$(RM) $(addsuffix *.gcno,$(addprefix $(PROFILE_DIR)/, $(object_dirs)))
 
 cocciclean:
+	$(RM) -r .build/contrib/coccinelle
 	$(RM) contrib/coccinelle/*.cocci.patch*
 
 clean: profile-clean coverage-clean cocciclean
diff --git a/contrib/coccinelle/tests/free.c b/contrib/coccinelle/tests/free.c
new file mode 100644
index 0000000000..96d4abc0c7
--- /dev/null
+++ b/contrib/coccinelle/tests/free.c
@@ -0,0 +1,11 @@
+int use_FREE_AND_NULL(int *v)
+{
+	free(*v);
+	*v = NULL;
+}
+
+int need_no_if(int *v)
+{
+	if (v)
+		free(v);
+}
diff --git a/contrib/coccinelle/tests/free.res b/contrib/coccinelle/tests/free.res
new file mode 100644
index 0000000000..f90fd9f48e
--- /dev/null
+++ b/contrib/coccinelle/tests/free.res
@@ -0,0 +1,9 @@
+int use_FREE_AND_NULL(int *v)
+{
+	FREE_AND_NULL(*v);
+}
+
+int need_no_if(int *v)
+{
+	free(v);
+}
diff --git a/shared.mak b/shared.mak
index 4330192e9c..33f43edbf9 100644
--- a/shared.mak
+++ b/shared.mak
@@ -70,6 +70,7 @@ ifndef V
 	QUIET_HDR      = @echo '   ' HDR $(<:hcc=h);
 	QUIET_RC       = @echo '   ' RC $@;
 	QUIET_SPATCH   = @echo '   ' SPATCH $<;
+	QUIET_SPATCH_T = @echo '   ' SPATCH TEST $(@:.build/%=%);
 
 ## Used in "Documentation/Makefile"
 	QUIET_ASCIIDOC	= @echo '   ' ASCIIDOC $@;