Merge pull request #381 from swiftwasm/yt/fix-sab-check-on-android

kateinoigakukun · web-flow · commit e854719ecf1f · 2025-07-03T19:22:06.000+09:00
Check if the memory is backed by a SAB by checking the constructor name
diff --git a/Plugins/PackageToJS/Templates/runtime.mjs b/Plugins/PackageToJS/Templates/runtime.mjs
@@ -308,7 +308,12 @@ class SwiftRuntime {
             // Cache the DataView as it's not a cheap operation
             let cachedDataView = new DataView(wasmMemory.buffer);
             let cachedUint8Array = new Uint8Array(wasmMemory.buffer);
-            if (typeof SharedArrayBuffer !== "undefined" && wasmMemory.buffer instanceof SharedArrayBuffer) {
+            // Check the constructor name of the buffer to determine if it's backed by a SharedArrayBuffer.
+            // We can't reference SharedArrayBuffer directly here because:
+            // 1. It may not be available in the global scope if the context is not cross-origin isolated.
+            // 2. The underlying buffer may be still backed by SAB even if the context is not cross-origin
+            //    isolated (e.g. localhost on Chrome on Android).
+            if (Object.getPrototypeOf(wasmMemory.buffer).constructor.name === "SharedArrayBuffer") {
                 // When the wasm memory is backed by a SharedArrayBuffer, growing the memory
                 // doesn't invalidate the data view by setting the byte length to 0. Instead,
                 // the data view points to an old buffer after growing the memory. So we have
@@ -796,8 +801,9 @@ class SwiftRuntime {
                     throw new Error("threadChannel is not set in options given to SwiftRuntime. Please set it to request transferring objects.");
                 }
                 const broker = getMessageBroker(this.options.threadChannel);
-                const sendingObjects = decodeObjectRefs(sending_objects, sending_objects_count, this.getDataView());
-                const transferringObjects = decodeObjectRefs(transferring_objects, transferring_objects_count, this.getDataView());
+                const dataView = this.getDataView();
+                const sendingObjects = decodeObjectRefs(sending_objects, sending_objects_count, dataView);
+                const transferringObjects = decodeObjectRefs(transferring_objects, transferring_objects_count, dataView);
                 broker.request({
                     type: "request",
                     data: {
diff --git a/Runtime/src/index.ts b/Runtime/src/index.ts
@@ -64,7 +64,13 @@ export class SwiftRuntime {
             // Cache the DataView as it's not a cheap operation
             let cachedDataView = new DataView(wasmMemory.buffer);
             let cachedUint8Array = new Uint8Array(wasmMemory.buffer);
-            if (typeof SharedArrayBuffer !== "undefined" && wasmMemory.buffer instanceof SharedArrayBuffer) {
+
+            // Check the constructor name of the buffer to determine if it's backed by a SharedArrayBuffer.
+            // We can't reference SharedArrayBuffer directly here because:
+            // 1. It may not be available in the global scope if the context is not cross-origin isolated.
+            // 2. The underlying buffer may be still backed by SAB even if the context is not cross-origin
+            //    isolated (e.g. localhost on Chrome on Android).
+            if (Object.getPrototypeOf(wasmMemory.buffer).constructor.name === "SharedArrayBuffer") {
                 // When the wasm memory is backed by a SharedArrayBuffer, growing the memory
                 // doesn't invalidate the data view by setting the byte length to 0. Instead,
                 // the data view points to an old buffer after growing the memory. So we have
