Add terminating NUL after __func__ string literal #2920

test/val/bug2920.c

@@ -0,0 +1,20 @@
+#include "unittest.h"
+
+TEST {
+    /* The bug causes __func__ to be not null terminated. */
+    const char *f = __func__;
+    size_t size = sizeof(__func__);
+    size_t i;
+
+    /* Ensure the size is correct (5 for "main" + null terminator) */
+    ASSERT_AreEqual((unsigned)size, 5u, "%u", "Sizeof __func__ should be 5");
+
+    /* Check content */
+    for (i = 0; i < size - 1; ++i) {
+        ASSERT_AreEqual(f[i], "main"[i], "%c", "Character mismatch");
+    }
+
+    /* Check null terminator specifically */
+    ASSERT_AreEqual(f[size - 1], '\0', "%02X", "Null terminator missing");
+}
+ENDTEST