test(wasm-actor): cycle 63 — zero-len send, overlapping regions, alloc exhaustion (274 tests)

Added 4 tests: zero-length payload from guest, overlapping dest/payload regions,
alloc exhaustion drops gracefully, stop all actors in runtime. No new bugs found.

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

crates/wasm-actor/tests/wasm_actor.rs

@@ -9223,4 +9223,145 @@ fn thirty_two_kb_payload_echo() {
     let resp = inbox.try_recv().expect("32KB echo");
     assert_eq!(resp.0.len(), 32768);
     assert_eq!(resp.0, payload);
+}
+
+// ── Cycle 63 ─────────────────────────────────────────────────────────────────
+
+// Guest sends with payload_len=0 but valid payload_ptr — zero-length payload delivered
+#[test]
+fn send_zero_length_payload_from_guest() {
+    let wat = r#"(module
+        (import "swactor" "send" (func $send (param i32 i32 i32)))
+        (memory (export "memory") 1)
+        (func (export "alloc") (param $len i32) (result i32) i32.const 1024)
+        (func (export "handle") (param $ptr i32) (param $len i32)
+            ;; Send with payload_len=0 — should deliver empty payload
+            (call $send (local.get $ptr) (i32.const 0) (i32.const 0))
+        )
+    )"#;
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wat::parse_str(wat).unwrap())
+        .build().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    let addr = rt.spawn(actor).unwrap();
+
+    // Frame message: first 32 bytes are dest (inbox addr)
+    let mut msg = Vec::with_capacity(32);
+    msg.extend_from_slice(&inbox.addr().0);
+    rt.send_to(addr, ByteMessage(msg)).unwrap();
+    rt.tick();
+
+    let resp = inbox.try_recv().expect("zero-length payload should arrive");
+    assert!(resp.0.is_empty(), "payload should be empty");
+}
+
+// Guest sends with overlapping dest and payload regions (payload starts inside dest)
+#[test]
+fn send_with_overlapping_dest_and_payload_regions() {
+    let wat = r#"(module
+        (import "swactor" "send" (func $send (param i32 i32 i32)))
+        (memory (export "memory") 1)
+        (func (export "alloc") (param $len i32) (result i32) i32.const 1024)
+        (func (export "handle") (param $ptr i32) (param $len i32)
+            ;; dest_ptr=1024, payload_ptr=1040 (inside the 32-byte dest region), payload_len=8
+            ;; This overlaps: dest is [1024..1056], payload is [1040..1048]
+            (call $send (i32.const 1024) (i32.const 1040) (i32.const 8))
+        )
+    )"#;
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wat::parse_str(wat).unwrap())
+        .build().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    let addr = rt.spawn(actor).unwrap();
+
+    // Write the inbox address into memory at offset 1024 (via the message)
+    let mut msg = Vec::with_capacity(64);
+    msg.extend_from_slice(&inbox.addr().0);
+    msg.extend_from_slice(&[0u8; 32]); // padding
+    rt.send_to(addr, ByteMessage(msg)).unwrap();
+    rt.tick();
+
+    // The send should succeed — overlapping reads are fine (read-only)
+    let resp = inbox.try_recv().expect("overlapping regions should work");
+    assert_eq!(resp.0.len(), 8);
+}
+
+// Sequential alloc exhaustion: echo actor with tiny heap eventually can't alloc
+#[test]
+fn alloc_exhaustion_drops_message_gracefully() {
+    let wat = r#"(module
+        (import "swactor" "send" (func $send (param i32 i32 i32)))
+        (memory (export "memory") 1)
+        ;; Tiny heap: starts at 60000, only 5536 bytes before page end
+        (global $heap (mut i32) (i32.const 60000))
+        (func (export "alloc") (param $len i32) (result i32)
+            (local $ptr i32)
+            (local.set $ptr (global.get $heap))
+            ;; Check if allocation would exceed page
+            (if (i32.gt_u
+                (i32.add (global.get $heap) (local.get $len))
+                (i32.const 65536))
+                (then (return (i32.const -1)))  ;; OOM signal
+            )
+            (global.set $heap (i32.add (global.get $heap) (local.get $len)))
+            (local.get $ptr)
+        )
+        (func (export "handle") (param $ptr i32) (param $len i32)
+            ;; Echo: send first 32 bytes as dest, rest as payload
+            (if (i32.ge_u (local.get $len) (i32.const 33))
+                (then
+                    (call $send
+                        (local.get $ptr)
+                        (i32.add (local.get $ptr) (i32.const 32))
+                        (i32.sub (local.get $len) (i32.const 32))
+                    )
+                )
+            )
+        )
+    )"#;
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wat::parse_str(wat).unwrap())
+        .build().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    let addr = rt.spawn(actor).unwrap();
+
+    // Send messages that consume heap space
+    for i in 0..100 {
+        rt.send_to(addr, framed_msg(inbox.addr(), &vec![i as u8; 100])).unwrap();
+    }
+    rt.tick();
+
+    // Count how many were echoed (some should be dropped due to OOM)
+    let delivered = std::iter::from_fn(|| inbox.try_recv()).count();
+    assert!(delivered < 100, "some messages should be dropped due to OOM (got {delivered})");
+    assert!(delivered > 0, "at least some messages should succeed");
+}
+
+// Stop all actors in a runtime — runtime should be empty
+#[test]
+fn stop_all_wasm_actors_in_runtime() {
+    let engine = SharedEngine::new().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let mut addrs = Vec::new();
+    for _ in 0..5 {
+        let actor = WasmActorBuilder::new(engine.clone(), guest_wasm("silent"))
+            .build().unwrap();
+        addrs.push(rt.spawn(actor).unwrap());
+    }
+    rt.tick();
+
+    for addr in &addrs {
+        rt.stop_actor(*addr);
+    }
+    rt.tick();
+    rt.tick();
+
+    // All actors stopped — sending should fail or be silently dropped
+    for addr in &addrs {
+        let _ = rt.send_to(*addr, ByteMessage(vec![]));
+    }
+    rt.tick(); // no panics
 }