[PATCH] vadidation: add used-to-be-signed unit tests

[Vincent Mailhol <mailhol@kernel.org>]

Add unit tests for the new used-to-be-signed check as introduced in [1]:

Results before applying [1]:

  $ ./test-suite used-to-be-signed.c
    TEST    used-to-be-signed (used-to-be-signed.c)
  error: actual error text does not match expected error text.
  error: see used-to-be-signed.c.error.* for further investigation.
  --- used-to-be-signed.c.error.expected	2025-09-23 00:50:07.079654644 +0900
  +++ used-to-be-signed.c.error.got	2025-09-23 00:50:07.073654719 +0900
  @@ -1,8 +0,0 @@
  -used-to-be-signed.c:8:19: warning: unsigned value that used to be signed checked against zero?
  -used-to-be-signed.c:6:33: signed value source
  -used-to-be-signed.c:11:17: warning: unsigned value that used to be signed checked against zero?
  -used-to-be-signed.c:6:33: signed value source
  -used-to-be-signed.c:14:20: warning: unsigned value that used to be signed checked against zero?
  -used-to-be-signed.c:6:33: signed value source
  -used-to-be-signed.c:17:18: warning: unsigned value that used to be signed checked against zero?
  -used-to-be-signed.c:6:33: signed value source
  error: FAIL: test 'used-to-be-signed.c' failed
  KO: out of 1 tests, 0 passed, 1 failed

...and after:

  $ ./test-suite used-to-be-signed.c
    TEST    used-to-be-signed (used-to-be-signed.c)
  OK: out of 1 tests, 1 passed, 0 failed

[1] Warn about "unsigned value that used to be signed against zero"
Link: https://lore.kernel.org/linux-sparse/20250921061337.3047616-1-mailhol@kernel.org/

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
Hi Chris,

Thanks for your guidance. I added more tests.

Because you asked me for my preference, I went for the single file.
But if you finally have a preference to split, tell me and I will
update.
---
 validation/used-to-be-signed.c | 49 ++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 validation/used-to-be-signed.c

diff --git a/validation/used-to-be-signed.c b/validation/used-to-be-signed.c
new file mode 100644
index 00000000..75eab7f3
--- /dev/null
+++ b/validation/used-to-be-signed.c
@@ -0,0 +1,49 @@
+void error(void);
+int check(void);
+
+static void positive_tests(unsigned int val)
+{
+	unsigned int ret = check();
+
+	if (ret < 0)
+		error();
+
+	if (0 > ret)
+		error();
+
+	if (ret >= 0)
+		/* Do stuff */;
+
+	if (0 <= ret)
+		/* Do stuff */;
+}
+
+static void negative_tests(unsigned int val)
+{
+	if (val < 0 || val > 42)
+		error();
+
+	if (0 > val || 42 < val)
+		error();
+
+	if (val >= 0 && val < 42)
+		/* Do stuff */;
+
+	if (0 <= val && 42 > val)
+		/* Do stuff */;
+}
+
+/*
+ * check-name: used-to-be-signed
+ *
+ * check-error-start
+used-to-be-signed.c:8:19: warning: unsigned value that used to be signed checked against zero?
+used-to-be-signed.c:6:33: signed value source
+used-to-be-signed.c:11:17: warning: unsigned value that used to be signed checked against zero?
+used-to-be-signed.c:6:33: signed value source
+used-to-be-signed.c:14:20: warning: unsigned value that used to be signed checked against zero?
+used-to-be-signed.c:6:33: signed value source
+used-to-be-signed.c:17:18: warning: unsigned value that used to be signed checked against zero?
+used-to-be-signed.c:6:33: signed value source
+ * check-error-end
+ */
-- 
2.49.1