[browser] js string marshaling by value

src/libraries/Common/src/Interop/Browser/Interop.Runtime.cs

@@ -24,10 +24,13 @@ internal static unsafe partial class Runtime
         public static extern unsafe void BindCSFunction(in string fully_qualified_name, int signature_hash, void* signature, out int is_exception, out object result);
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern void ResolveOrRejectPromise(void* data);
+
+#if !ENABLE_JS_INTEROP_BY_VALUE
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern IntPtr RegisterGCRoot(IntPtr start, int bytesSize, IntPtr name);
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern void DeregisterGCRoot(IntPtr handle);
+#endif
 
 #if FEATURE_WASM_THREADS
         [MethodImpl(MethodImplOptions.InternalCall)]

src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj

@@ -12,9 +12,12 @@
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' != 'browser'">SR.SystemRuntimeInteropServicesJavaScript_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
     <FeatureWasmThreads Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
+    <WasmEnableJsInteropByValue Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableJsInteropByValue)' == '' and '$(FeatureWasmThreads)' == 'true'">true</WasmEnableJsInteropByValue>
+    <WasmEnableJsInteropByValue Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableJsInteropByValue)' == ''">false</WasmEnableJsInteropByValue>
     <WasmEnableLegacyJsInterop Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
     <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'" >$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
     <DefineConstants Condition="'$(WasmEnableLegacyJsInterop)' == 'false'" >$(DefineConstants);DISABLE_LEGACY_JS_INTEROP</DefineConstants>
+    <DefineConstants Condition="'$(WasmEnableJsInteropByValue)' == 'true'" >$(DefineConstants);ENABLE_JS_INTEROP_BY_VALUE</DefineConstants>
     <EmitCompilerGeneratedFiles Condition="'$(Configuration)' == 'Debug' and '$(TargetPlatformIdentifier)' == 'browser'">true</EmitCompilerGeneratedFiles>
   </PropertyGroup>
 

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Object.cs

@@ -344,7 +344,9 @@ public unsafe void ToManaged(out object?[]? value)
                 arg.ToManaged(out val);
                 value[i] = val;
             }
+#if !ENABLE_JS_INTEROP_BY_VALUE
             Interop.Runtime.DeregisterGCRoot(slot.IntPtrValue);
+#endif
             Marshal.FreeHGlobal(slot.IntPtrValue);
         }
 
@@ -366,7 +368,9 @@ public unsafe void ToJS(object?[] value)
             slot.Type = MarshalerType.Array;
             JSMarshalerArgument* payload = (JSMarshalerArgument*)Marshal.AllocHGlobal(bytes);
             Unsafe.InitBlock(payload, 0, (uint)bytes);
+#if !ENABLE_JS_INTEROP_BY_VALUE
             Interop.Runtime.RegisterGCRoot((IntPtr)payload, bytes, IntPtr.Zero);
+#endif
             for (int i = 0; i < slot.Length; i++)
             {
                 ref JSMarshalerArgument arg = ref payload[i];

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.String.cs

@@ -20,11 +20,15 @@ public unsafe void ToManaged(out string? value)
                 value = null;
                 return;
             }
-
+#if ENABLE_JS_INTEROP_BY_VALUE
+            value = Marshal.PtrToStringUni(slot.IntPtrValue, slot.Length);
+            Marshal.FreeHGlobal(slot.IntPtrValue);
+#else
             fixed (void* argAsRoot = &slot.IntPtrValue)
             {
                 value = Unsafe.AsRef<string>(argAsRoot);
             }
+#endif
         }
 
         /// <summary>
@@ -42,6 +46,10 @@ public unsafe void ToJS(string? value)
             else
             {
                 slot.Type = MarshalerType.String;
+#if ENABLE_JS_INTEROP_BY_VALUE
+                slot.IntPtrValue = Marshal.StringToHGlobalUni(value); // alloc, JS side will free
+                slot.Length = value.Length;
+#else
                 // here we treat JSMarshalerArgument.IntPtrValue as root, because it's allocated on stack
                 // or we register the buffer with JSFunctionBinding._RegisterGCRoot
                 // We assume that GC would keep updating on GC move
@@ -52,6 +60,7 @@ public unsafe void ToJS(string? value)
                     var currentRoot = (IntPtr*)Unsafe.AsPointer(ref cpy);
                     argAsRoot[0] = currentRoot[0];
                 }
+#endif
             }
         }
 
@@ -78,7 +87,9 @@ public unsafe void ToManaged(out string?[]? value)
                 arg.ToManaged(out val);
                 value[i] = val;
             }
+#if !ENABLE_JS_INTEROP_BY_VALUE
             Interop.Runtime.DeregisterGCRoot(slot.IntPtrValue);
+#endif
             Marshal.FreeHGlobal(slot.IntPtrValue);
         }
 
@@ -100,7 +111,9 @@ public unsafe void ToJS(string?[] value)
             slot.Type = MarshalerType.Array;
             JSMarshalerArgument* payload = (JSMarshalerArgument*)Marshal.AllocHGlobal(bytes);
             Unsafe.InitBlock(payload, 0, (uint)bytes);
+#if !ENABLE_JS_INTEROP_BY_VALUE
             Interop.Runtime.RegisterGCRoot((IntPtr)payload, bytes, IntPtr.Zero);
+#endif
             for (int i = 0; i < slot.Length; i++)
             {
                 ref JSMarshalerArgument arg = ref payload[i];

src/mono/wasm/build/WasmApp.Native.targets

@@ -245,6 +245,7 @@
       <_EmccCFlags Include="-DENABLE_AOT_PROFILER=1"           Condition="$(WasmProfilers.Contains('aot'))" />
       <_EmccCFlags Include="-DENABLE_BROWSER_PROFILER=1"       Condition="$(WasmProfilers.Contains('browser'))" />
       <_EmccCFlags Include="-DDISABLE_LEGACY_JS_INTEROP=1"     Condition="'$(WasmEnableLegacyJsInterop)' == 'false'" />
+      <_EmccCFlags Include="-DENABLE_JS_INTEROP_BY_VALUE=1"    Condition="'$(WasmEnableJsInteropByValue)' == 'true'" />
 
       <_EmccCFlags Include="-DGEN_PINVOKE=1" />
       <_EmccCFlags Include="-emit-llvm" />
@@ -288,6 +289,8 @@
       <EmscriptenEnvVars Include="EM_FROZEN_CACHE=True" Condition="'$(WasmCachePath)' == '$(EmscriptenCacheSdkCacheDir)'" />
       <EmscriptenEnvVars Include="DISABLE_LEGACY_JS_INTEROP=1" Condition="'$(WasmEnableLegacyJsInterop)' == 'false'" />
       <EmscriptenEnvVars Include="DISABLE_LEGACY_JS_INTEROP=0" Condition="'$(WasmEnableLegacyJsInterop)' != 'false'" />
+      <EmscriptenEnvVars Include="ENABLE_JS_INTEROP_BY_VALUE=1" Condition="'$(WasmEnableJsInteropByValue)' == 'true'" />
+      <EmscriptenEnvVars Include="ENABLE_JS_INTEROP_BY_VALUE=0" Condition="'$(WasmEnableJsInteropByValue)' != 'true'" />
       <EmscriptenEnvVars Include="WASM_ENABLE_SIMD=1" Condition="'$(WasmEnableSIMD)' != 'false'" />
       <EmscriptenEnvVars Include="WASM_ENABLE_SIMD=0" Condition="'$(WasmEnableSIMD)' == 'false'" />
       <EmscriptenEnvVars Include="WASM_ENABLE_EH=1" Condition="'$(WasmEnableExceptionHandling)' != 'false'" />

src/mono/wasm/build/WasmApp.targets

@@ -73,6 +73,7 @@
                                               Defaults to false.
       - $(WasmAotProfilePath)               - Path to an AOT profile file.
       - $(WasmEnableLegacyJsInterop)        - Include support for legacy JS interop. Defaults to true.
+      - $(WasmEnableJsInteropByValue)       - Make JS interop to pass string by value instead of by reference. Defaults to false. Defaults to true for build with threads.
       - $(WasmEnableExceptionHandling)      - Enable support for the WASM post MVP Exception Handling runtime extension.
       - $(WasmEnableSIMD)                   - Enable support for the WASM post MVP SIMD runtime extension.
       - $(WasmEnableWebcil)                 - Enable conversion of assembly .dlls to Webcil wrapped in .wasm (default: true)
@@ -115,6 +116,8 @@
     <WasmEnableExceptionHandling Condition="'$(WasmEnableExceptionHandling)' == ''">true</WasmEnableExceptionHandling>
     <WasmEnableSIMD Condition="'$(WasmEnableSIMD)' == ''">$(WasmEnableExceptionHandling)</WasmEnableSIMD>
     <WasmEnableLegacyJsInterop Condition="'$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
+    <WasmEnableJsInteropByValue Condition="'$(WasmEnableJsInteropByValue)' == '' and ( '$(WasmEnableThreads)' == 'true' or '$(MonoWasmBuildVariant)' == 'multithread' )">true</WasmEnableJsInteropByValue>
+    <WasmEnableJsInteropByValue Condition="'$(WasmEnableJsInteropByValue)' == ''">false</WasmEnableJsInteropByValue>
 
     <!--<WasmStripAOTAssemblies Condition="'$(AOTMode)' == 'LLVMOnlyInterp'">false</WasmStripAOTAssemblies>-->
     <!--<WasmStripAOTAssemblies Condition="'$(WasmStripAOTAssemblies)' == ''">$(RunAOTCompilation)</WasmStripAOTAssemblies>-->

src/mono/wasm/runtime/CMakeLists.txt

@@ -4,6 +4,7 @@ project(mono-wasm-runtime C)
 
 option(DISABLE_THREADS "defined if the build does NOT support multithreading" ON)
 option(DISABLE_LEGACY_JS_INTEROP "defined if the build does not support legacy JavaScript interop" OFF)
+option(ENABLE_JS_INTEROP_BY_VALUE "defined when JS interop without pointers to managed objects" OFF)
 
 set(CMAKE_EXECUTABLE_SUFFIX ".js")
 add_executable(dotnet.native corebindings.c driver.c pinvoke.c)

src/mono/wasm/runtime/corebindings.c

@@ -66,8 +66,11 @@ void bindings_initialize_internals (void)
 	mono_add_internal_call ("Interop/Runtime::InvokeJSImport", mono_wasm_invoke_js_import);
 	mono_add_internal_call ("Interop/Runtime::BindCSFunction", mono_wasm_bind_cs_function);
 	mono_add_internal_call ("Interop/Runtime::ResolveOrRejectPromise", mono_wasm_resolve_or_reject_promise);
+
+#ifndef	ENABLE_JS_INTEROP_BY_VALUE
 	mono_add_internal_call ("Interop/Runtime::RegisterGCRoot", mono_wasm_register_root);
 	mono_add_internal_call ("Interop/Runtime::DeregisterGCRoot", mono_wasm_deregister_root);
+#endif /* ENABLE_JS_INTEROP_BY_VALUE */
 
 #ifndef DISABLE_THREADS
 	mono_add_internal_call ("Interop/Runtime::InstallWebWorkerInterop", mono_wasm_install_js_worker_interop);

src/mono/wasm/runtime/marshal-to-cs.ts

@@ -3,6 +3,7 @@
 
 import MonoWasmThreads from "consts:monoWasmThreads";
 import BuildConfiguration from "consts:configuration";
+import WasmEnableJsInteropByValue from "consts:wasmEnableJsInteropByValue";
 
 import { isThenable } from "./cancelable-promise";
 import cwraps from "./cwraps";
@@ -18,7 +19,7 @@ import {
 } from "./marshal";
 import { get_marshaler_to_js_by_type } from "./marshal-to-js";
 import { _zero_region, localHeapViewF64, localHeapViewI32, localHeapViewU8 } from "./memory";
-import { stringToMonoStringRoot } from "./strings";
+import { stringToMonoStringRoot, stringToUTF16 } from "./strings";
 import { JSMarshalerArgument, JSMarshalerArguments, JSMarshalerType, MarshalerToCs, MarshalerToJs, BoundMarshalerToCs, MarshalerType } from "./types/internal";
 import { TypedArray } from "./types/emscripten";
 import { addUnsettledPromise, settleUnsettledPromise } from "./pthreads/shared/eventloop";
@@ -229,12 +230,20 @@ function _marshal_string_to_cs(arg: JSMarshalerArgument, value: string) {
 }
 
 function _marshal_string_to_cs_impl(arg: JSMarshalerArgument, value: string) {
-    const root = get_string_root(arg);
-    try {
-        stringToMonoStringRoot(value, root);
-    }
-    finally {
-        root.release();
+    if (WasmEnableJsInteropByValue) {
+        const bufferLen = value.length * 2;
+        const buffer = Module._malloc(bufferLen);
+        stringToUTF16(buffer as any, buffer as any + bufferLen, value);
+        set_arg_intptr(arg, buffer);
+        set_arg_length(arg, value.length);
+    } else {
+        const root = get_string_root(arg);
+        try {
+            stringToMonoStringRoot(value, root);
+        }
+        finally {
+            root.release();
+        }
     }
 }
 
@@ -505,7 +514,9 @@ export function marshal_array_to_cs_impl(arg: JSMarshalerArgument, value: Array<
         if (element_type == MarshalerType.String) {
             mono_check(Array.isArray(value), "Value is not an Array");
             _zero_region(buffer_ptr, buffer_length);
-            cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
+            if (!WasmEnableJsInteropByValue) {
+                cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
+            }
             for (let index = 0; index < length; index++) {
                 const element_arg = get_arg(<any>buffer_ptr, index);
                 _marshal_string_to_cs(element_arg, value[index]);
@@ -514,7 +525,9 @@ export function marshal_array_to_cs_impl(arg: JSMarshalerArgument, value: Array<
         else if (element_type == MarshalerType.Object) {
             mono_check(Array.isArray(value), "Value is not an Array");
             _zero_region(buffer_ptr, buffer_length);
-            cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
+            if (!WasmEnableJsInteropByValue) {
+                cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
+            }
             for (let index = 0; index < length; index++) {
                 const element_arg = get_arg(<any>buffer_ptr, index);
                 _marshal_cs_object_to_cs(element_arg, value[index]);

src/mono/wasm/runtime/marshal-to-js.ts

@@ -3,6 +3,7 @@
 
 import MonoWasmThreads from "consts:monoWasmThreads";
 import BuildConfiguration from "consts:configuration";
+import WasmEnableJsInteropByValue from "consts:wasmEnableJsInteropByValue";
 
 import cwraps from "./cwraps";
 import { _lookup_js_owned_object, mono_wasm_get_jsobj_from_js_handle, mono_wasm_release_cs_owned_object, register_with_jsv_handle, setup_managed_proxy, teardown_managed_proxy } from "./gc-handles";
@@ -15,7 +16,7 @@ import {
     get_signature_res_type, get_arg_u16, array_element_size, get_string_root,
     ArraySegment, Span, MemoryViewType, get_signature_arg3_type, get_arg_i64_big, get_arg_intptr, get_arg_element_type, JavaScriptMarshalerArgSize, proxy_debug_symbol
 } from "./marshal";
-import { monoStringToString } from "./strings";
+import { monoStringToString, utf16ToString } from "./strings";
 import { GCHandleNull, JSMarshalerArgument, JSMarshalerArguments, JSMarshalerType, MarshalerToCs, MarshalerToJs, BoundMarshalerToJs, MarshalerType } from "./types/internal";
 import { TypedArray } from "./types/emscripten";
 import { get_marshaler_to_cs_by_type, jsinteropDoc, marshal_exception_to_cs } from "./marshal-to-cs";
@@ -310,12 +311,21 @@ export function marshal_string_to_js(arg: JSMarshalerArgument): string | null {
     if (type == MarshalerType.None) {
         return null;
     }
-    const root = get_string_root(arg);
-    try {
-        const value = monoStringToString(root);
+    if (WasmEnableJsInteropByValue) {
+        const buffer = get_arg_intptr(arg);
+        const len = get_arg_length(arg) * 2;
+        const value = utf16ToString(<any>buffer, <any>buffer + len);
+        Module._free(buffer as any);
         return value;
-    } finally {
-        root.release();
+    }
+    else {
+        const root = get_string_root(arg);
+        try {
+            const value = monoStringToString(root);
+            return value;
+        } finally {
+            root.release();
+        }
     }
 }
 
@@ -421,15 +431,19 @@ function _marshal_array_to_js_impl(arg: JSMarshalerArgument, element_type: Marsh
             const element_arg = get_arg(<any>buffer_ptr, index);
             result[index] = marshal_string_to_js(element_arg);
         }
-        cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
+        if (!WasmEnableJsInteropByValue) {
+            cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
+        }
     }
     else if (element_type == MarshalerType.Object) {
         result = new Array(length);
         for (let index = 0; index < length; index++) {
             const element_arg = get_arg(<any>buffer_ptr, index);
             result[index] = _marshal_cs_object_to_js(element_arg);
         }
-        cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
+        if (!WasmEnableJsInteropByValue) {
+            cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
+        }
     }
     else if (element_type == MarshalerType.JSObject) {
         result = new Array(length);

src/mono/wasm/runtime/rollup.config.js

@@ -23,6 +23,7 @@ const monoWasmThreads = process.env.MonoWasmThreads === "true" ? true : false;
 const wasmEnableSIMD = process.env.WASM_ENABLE_SIMD === "1" ? true : false;
 const wasmEnableExceptionHandling = process.env.WASM_ENABLE_EH === "1" ? true : false;
 const wasmEnableLegacyJsInterop = process.env.DISABLE_LEGACY_JS_INTEROP !== "1" ? true : false;
+const wasmEnableJsInteropByValue = process.env.ENABLE_JS_INTEROP_BY_VALUE == "1" ? true : false;
 const monoDiagnosticsMock = process.env.MonoDiagnosticsMock === "true" ? true : false;
 // because of stack walk at src/mono/wasm/debugger/BrowserDebugProxy/MonoProxy.cs
 // and unit test at src\libraries\System.Runtime.InteropServices.JavaScript\tests\System.Runtime.InteropServices.JavaScript.Legacy.UnitTests\timers.mjs
@@ -103,6 +104,7 @@ const envConstants = {
     monoDiagnosticsMock,
     gitHash,
     wasmEnableLegacyJsInterop,
+    wasmEnableJsInteropByValue,
     isContinuousIntegrationBuild,
 };
 

src/mono/wasm/runtime/wasm-config.h.in

@@ -10,4 +10,7 @@
 /* Support for legacy JS interop is disabled */
 #cmakedefine DISABLE_LEGACY_JS_INTEROP
 
+/* Support for JS interop without pointers to managed objects */
+#cmakedefine ENABLE_JS_INTEROP_BY_VALUE
+
 #endif/*__MONO_WASM_CONFIG_H__*/