From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thibaud Michaud <thibaudm@chromium.org>
Date: Thu, 10 Oct 2024 18:54:04 +0200
Subject: Merged: [wasm] Fix default externref/exnref reference

- The default nullexternref should be null instead of undefined
- The default exnref/nullexnref should be null instead of wasm_null

(cherry picked from commit e7ccf0af1bdddd20dc58e1790a94739dba0209a3)

Change-Id: I5b32e80f2eb59b29113232f9e2f59a8803915cb3
Fixed: 372285204,372269618
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5937812
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Auto-Submit: Matthias Liedtke <mliedtke@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/branch-heads/13.0@{#35}
Cr-Branched-From: 4be854bd71ea878a25b236a27afcecffa2e29360-refs/heads/13.0.245@{#1}
Cr-Branched-From: 1f5183f7ad6cca21029fd60653d075730c644432-refs/heads/main@{#96103}

diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index 32bbbce5838a65c62d419bb7b79a36827d7b97f2..0d24a204f68a64bb65c7b102fe52571e23fe29a0 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -1314,9 +1314,12 @@ i::Handle<i::HeapObject> DefaultReferenceValue(i::Isolate* isolate,
   DCHECK(type.is_object_reference());
   // Use undefined for JS type (externref) but null for wasm types as wasm does
   // not know undefined.
-  if (type.heap_representation() == i::wasm::HeapType::kExtern ||
-      type.heap_representation() == i::wasm::HeapType::kNoExtern) {
+  if (type.heap_representation() == i::wasm::HeapType::kExtern) {
     return isolate->factory()->undefined_value();
+  } else if (type.heap_representation() == i::wasm::HeapType::kNoExtern ||
+             type.heap_representation() == i::wasm::HeapType::kExn ||
+             type.heap_representation() == i::wasm::HeapType::kNoExn) {
+    return isolate->factory()->null_value();
   }
   return isolate->factory()->wasm_null();
 }