7 files changed, 119 insertions, 10 deletions
diff --git a/builtin/fetch.c b/builtin/fetch.c
index ac29c2b1ae..8a3ae71fed 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1113,7 +1113,7 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 			      struct fetch_head *fetch_head, struct worktree **worktrees)
 {
 	int url_len, i, rc = 0;
-	struct strbuf note = STRBUF_INIT, err = STRBUF_INIT;
+	struct strbuf note = STRBUF_INIT;
 	const char *what, *kind;
 	struct ref *rm;
 	char *url;
@@ -1281,7 +1281,6 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 
  abort:
 	strbuf_release(&note);
-	strbuf_release(&err);
 	free(url);
 	return rc;
 }
diff --git a/builtin/merge.c b/builtin/merge.c
index d9784d4891..23170f2d2a 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -375,7 +375,6 @@ static void reset_hard(const struct object_id *oid, int verbose)
 static void restore_state(const struct object_id *head,
 			  const struct object_id *stash)
 {
-	struct strbuf sb = STRBUF_INIT;
 	const char *args[] = { "stash", "apply", NULL, NULL };
 
 	if (is_null_oid(stash))
@@ -391,7 +390,6 @@ static void restore_state(const struct object_id *head,
 	 */
 	run_command_v_opt(args, RUN_GIT_CMD);
 
-	strbuf_release(&sb);
 	refresh_cache(REFRESH_QUIET);
 }
 
@@ -502,7 +500,6 @@ static void merge_name(const char *remote, struct strbuf *msg)
 {
 	struct commit *remote_head;
 	struct object_id branch_head;
-	struct strbuf buf = STRBUF_INIT;
 	struct strbuf bname = STRBUF_INIT;
 	struct merge_remote_desc *desc;
 	const char *ptr;
@@ -590,7 +587,6 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		oid_to_hex(&remote_head->object.oid), remote);
 cleanup:
 	free(found_ref);
-	strbuf_release(&buf);
 	strbuf_release(&bname);
 }
 
diff --git a/contrib/coccinelle/tests/unused.c b/contrib/coccinelle/tests/unused.c
new file mode 100644
index 0000000000..495ae58ccf
--- /dev/null
+++ b/contrib/coccinelle/tests/unused.c
@@ -0,0 +1,55 @@
+void test_strbuf(void)
+{
+	struct strbuf sb1 = STRBUF_INIT;
+	struct strbuf sb2 = STRBUF_INIT;
+	struct strbuf sb3 = STRBUF_INIT;
+	struct strbuf sb4 = STRBUF_INIT;
+	struct strbuf sb5;
+	struct strbuf sb6 = { 0 };
+	struct strbuf sb7 = STRBUF_INIT;
+	struct strbuf sb8 = STRBUF_INIT;
+	struct strbuf *sp1;
+	struct strbuf *sp2;
+	struct strbuf *sp3;
+	struct strbuf *sp4 = xmalloc(sizeof(struct strbuf));
+	struct strbuf *sp5 = xmalloc(sizeof(struct strbuf));
+	struct strbuf *sp6 = xmalloc(sizeof(struct strbuf));
+	struct strbuf *sp7;
+
+	strbuf_init(&sb5, 0);
+	strbuf_init(sp1, 0);
+	strbuf_init(sp2, 0);
+	strbuf_init(sp3, 0);
+	strbuf_init(sp4, 0);
+	strbuf_init(sp5, 0);
+	strbuf_init(sp6, 0);
+	strbuf_init(sp7, 0);
+	sp7 = xmalloc(sizeof(struct strbuf));
+
+	use_before(&sb3);
+	use_as_str("%s", sb7.buf);
+	use_as_str("%s", sp1->buf);
+	use_as_str("%s", sp6->buf);
+	pass_pp(&sp3);
+
+	strbuf_release(&sb1);
+	strbuf_reset(&sb2);
+	strbuf_release(&sb3);
+	strbuf_release(&sb4);
+	strbuf_release(&sb5);
+	strbuf_release(&sb6);
+	strbuf_release(&sb7);
+	strbuf_release(sp1);
+	strbuf_release(sp2);
+	strbuf_release(sp3);
+	strbuf_release(sp4);
+	strbuf_release(sp5);
+	strbuf_release(sp6);
+	strbuf_release(sp7);
+
+	use_after(&sb4);
+
+	if (when_strict())
+		return;
+	strbuf_release(&sb8);
+}
diff --git a/contrib/coccinelle/tests/unused.res b/contrib/coccinelle/tests/unused.res
new file mode 100644
index 0000000000..b3b71053ed
--- /dev/null
+++ b/contrib/coccinelle/tests/unused.res
@@ -0,0 +1,30 @@
+void test_strbuf(void)
+{
+	struct strbuf sb3 = STRBUF_INIT;
+	struct strbuf sb4 = STRBUF_INIT;
+	struct strbuf sb7 = STRBUF_INIT;
+	struct strbuf *sp1;
+	struct strbuf *sp3;
+	struct strbuf *sp6 = xmalloc(sizeof(struct strbuf));
+	strbuf_init(sp1, 0);
+	strbuf_init(sp3, 0);
+	strbuf_init(sp6, 0);
+
+	use_before(&sb3);
+	use_as_str("%s", sb7.buf);
+	use_as_str("%s", sp1->buf);
+	use_as_str("%s", sp6->buf);
+	pass_pp(&sp3);
+
+	strbuf_release(&sb3);
+	strbuf_release(&sb4);
+	strbuf_release(&sb7);
+	strbuf_release(sp1);
+	strbuf_release(sp3);
+	strbuf_release(sp6);
+
+	use_after(&sb4);
+
+	if (when_strict())
+		return;
+}
diff --git a/contrib/coccinelle/unused.cocci b/contrib/coccinelle/unused.cocci
new file mode 100644
index 0000000000..56530498d1
--- /dev/null
+++ b/contrib/coccinelle/unused.cocci
@@ -0,0 +1,32 @@
+// This rule finds sequences of "unused" declerations and uses of a
+// variable, where "unused" is defined to include only calling the
+// equivalent of alloc, init & free functions on the variable.
+@@
+type T;
+identifier I;
+constant INIT_MACRO =~ "^STRBUF_INIT$";
+identifier MALLOC1 =~ "^x?[mc]alloc$";
+identifier INIT_CALL1 =~ "^strbuf_init$";
+identifier REL1 =~ "^strbuf_(release|reset)$";
+@@
+
+(
+- T I;
+|
+- T I = { 0 };
+|
+- T I = INIT_MACRO;
+|
+- T I = MALLOC1(...);
+)
+
+<... when != \( I \| &I \)
+(
+- \( INIT_CALL1 \)( \( I \| &I \), ...);
+|
+- I = MALLOC1(...);
+)
+...>
+
+- \( REL1 \)( \( &I \| I \) );
+  ... when != \( I \| &I \)
diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c
index 28176914e5..97e71fe19c 100644
--- a/contrib/scalar/scalar.c
+++ b/contrib/scalar/scalar.c
@@ -687,7 +687,7 @@ static int cmd_diagnose(int argc, const char **argv)
 	int stdout_fd = -1, archiver_fd = -1;
 	time_t now = time(NULL);
 	struct tm tm;
-	struct strbuf path = STRBUF_INIT, buf = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT;
 	int res = 0;
 
 	argc = parse_options(argc, argv, NULL, options,
@@ -779,7 +779,6 @@ diagnose_cleanup:
 	free(argv_copy);
 	strvec_clear(&archiver_args);
 	strbuf_release(&zip_path);
-	strbuf_release(&path);
 	strbuf_release(&buf);
 
 	return res;
diff --git a/diff.c b/diff.c
index e71cf75886..d4290615aa 100644
--- a/diff.c
+++ b/diff.c
@@ -1289,7 +1289,6 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 {
 	static const char *nneof = " No newline at end of file\n";
 	const char *context, *reset, *set, *set_sign, *meta, *fraginfo;
-	struct strbuf sb = STRBUF_INIT;
 
 	enum diff_symbol s = eds->s;
 	const char *line = eds->line;
@@ -1521,7 +1520,6 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 	default:
 		BUG("unknown diff symbol");
 	}
-	strbuf_release(&sb);
 }
 
 static void emit_diff_symbol(struct diff_options *o, enum diff_symbol s,