test: Cycle 18 — div-by-zero trap, extra exports, zero-addr send, operation sequence fuzz

Authored by Claude, lovingly guided by Zachery Aaron Shores-Chmielewski

crates/wasm-actor/tests/wasm_actor.rs

@@ -3184,3 +3184,158 @@ fn two_watchers_both_notified_when_wasm_actor_dies() {
     assert_eq!(count_a.load(std::sync::atomic::Ordering::SeqCst), 1, "watcher A should be notified");
     assert_eq!(count_b.load(std::sync::atomic::Ordering::SeqCst), 1, "watcher B should be notified");
 }
+
+// ── Division by zero: WASM trap, actor survives ─────────────────────────────
+
+#[test]
+fn guest_division_by_zero_traps_actor_survives() {
+    let wat = r#"
+        (module
+            (import "swactor" "send" (func $send (param i32 i32 i32)))
+            (memory (export "memory") 1)
+            (func (export "alloc") (param i32) (result i32) i32.const 256)
+            (func (export "handle") (param $ptr i32) (param $len i32)
+                ;; Division by zero is a trap in WASM
+                local.get $len
+                i32.const 0
+                i32.div_u
+                drop
+            )
+        )
+    "#;
+    let wasm = wat::parse_str(wat).unwrap();
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wasm).build().unwrap();
+
+    let rt = Runtime::new(RuntimeConfig::default());
+    let addr = rt.spawn(actor).unwrap();
+
+    rt.send_to(addr, ByteMessage(vec![1])).unwrap();
+    rt.tick(); // div by zero trap
+
+    // Actor survives
+    rt.send_to(addr, ByteMessage(vec![2])).unwrap();
+    rt.tick();
+}
+
+// ── Module with extra exports: globals and extra functions ──────────────────
+
+#[test]
+fn module_with_extra_exports_builds_and_works() {
+    // Module exports extra globals and functions beyond the required ones.
+    // Builder should ignore them.
+    let wat = r#"
+        (module
+            (import "swactor" "send" (func $send (param i32 i32 i32)))
+            (memory (export "memory") 1)
+            (global (export "version") i32 (i32.const 42))
+            (global (export "magic") i64 (i64.const 12345))
+            (func (export "alloc") (param i32) (result i32) i32.const 256)
+            (func (export "handle") (param $ptr i32) (param $len i32)
+                (i32.store8 (i32.const 200) (i32.const 7))
+                local.get $ptr
+                i32.const 200
+                i32.const 1
+                call $send
+            )
+            (func (export "extra_func") (param i32) (result i32)
+                local.get 0
+            )
+        )
+    "#;
+    let wasm = wat::parse_str(wat).unwrap();
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wasm).build().unwrap();
+
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    let addr = rt.spawn(actor).unwrap();
+
+    rt.send_to(addr, framed_msg(inbox.addr(), b"extras")).unwrap();
+    rt.tick();
+
+    let received = inbox.try_recv().expect("module with extras should work");
+    assert_eq!(received.0, vec![7]);
+}
+
+// ── Send with dest_ptr=0, all zeroes in memory: valid but unroutable ────────
+
+#[test]
+fn send_with_all_zero_dest_from_uninitialized_memory() {
+    // Guest reads dest address from offset 500 (uninitialized, all zeros).
+    // The zero address isn't routable. ctx.send fails silently.
+    let wat = r#"
+        (module
+            (import "swactor" "send" (func $send (param i32 i32 i32)))
+            (memory (export "memory") 1)
+            (func (export "alloc") (param i32) (result i32) i32.const 256)
+            (func (export "handle") (param i32 i32)
+                ;; Read dest from uninitialized region (offset 500, all zeros)
+                i32.const 500   ;; dest_ptr
+                i32.const 32    ;; payload_ptr
+                i32.const 1     ;; payload_len
+                call $send
+            )
+        )
+    "#;
+    let wasm = wat::parse_str(wat).unwrap();
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wasm).build().unwrap();
+
+    let rt = Runtime::new(RuntimeConfig::default());
+    let addr = rt.spawn(actor).unwrap();
+
+    rt.send_to(addr, ByteMessage(vec![1, 2, 3])).unwrap();
+    rt.tick(); // send to zero-address fails silently
+
+    // Actor survives
+    rt.send_to(addr, ByteMessage(vec![4])).unwrap();
+    rt.tick();
+}
+
+// ── Property: WASM actor survives any sequence of operations ────────────────
+
+proptest! {
+    #[test]
+    fn prop_actor_survives_any_operation_sequence(
+        ops in proptest::collection::vec(
+            prop_oneof![
+                Just("send"),
+                Just("empty"),
+                Just("large"),
+            ],
+            1..20
+        )
+    ) {
+        let engine = SharedEngine::new().unwrap();
+        let actor = WasmActorBuilder::new(engine, guest_wasm("echo"))
+            .build()
+            .unwrap();
+
+        let rt = Runtime::new(RuntimeConfig::default());
+        let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+        let addr = rt.spawn(actor).unwrap();
+
+        for op in &ops {
+            match *op {
+                "send" => {
+                    rt.send_to(addr, framed_msg(inbox.addr(), b"msg")).unwrap();
+                }
+                "empty" => {
+                    rt.send_to(addr, ByteMessage(vec![])).unwrap();
+                }
+                "large" => {
+                    rt.send_to(addr, ByteMessage(vec![0u8; 60000])).unwrap();
+                }
+                _ => unreachable!(),
+            }
+            rt.tick();
+            // Drain inbox
+            while inbox.try_recv().is_some() {}
+        }
+
+        // Actor should still be alive
+        let result = rt.send_to(addr, ByteMessage(vec![99]));
+        prop_assert!(result.is_ok(), "actor must survive any operation sequence");
+    }
+}