[wasm][wasi] Allow to build wasi in library mode

eng/testing/scenarios/BuildWasiAppsJobsList.txt

@@ -4,3 +4,4 @@ Wasi.Build.Tests.SdkMissingTests
 Wasi.Build.Tests.RuntimeConfigTests
 Wasi.Build.Tests.WasiTemplateTests
 Wasi.Build.Tests.PInvokeTableGeneratorTests
+Wasi.Build.Tests.WasiLibraryModeTests

src/mono/browser/runtime/runtime.h

@@ -20,5 +20,6 @@ MonoAssembly *mono_wasm_assembly_load (const char *name);
 MonoClass *mono_wasm_assembly_find_class (MonoAssembly *assembly, const char *namespace, const char *name);
 MonoMethod *mono_wasm_assembly_find_method (MonoClass *klass, const char *name, int arguments);
 void mono_wasm_marshal_get_managed_wrapper (const char* assemblyName, const char* typeName, const char* methodName, int num_params);
+int initialize_runtime ();
 
 #endif

src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk/Sdk/Sdk.props

@@ -3,7 +3,7 @@
     <TargetArchitecture>wasm</TargetArchitecture>
     <TargetOS>wasi</TargetOS>
     <UseMonoRuntime>true</UseMonoRuntime>
-    <OutputType>Exe</OutputType>
+    <OutputType Condition="'$(OutputType)' == ''">Exe</OutputType>
     <PublishTrimmed Condition="'$(PublishTrimmed)' == ''">true</PublishTrimmed>
   </PropertyGroup>
 </Project>

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Pack.props

@@ -15,6 +15,5 @@ Copyright (c) .NET Foundation. All rights reserved.
   </PropertyGroup>
   <PropertyGroup Condition="'$(RuntimeIdentifier)' == 'browser-wasm'">
     <_WebAssemblyPropsFile>$(MSBuildThisFileDirectory)\Microsoft.NET.Sdk.WebAssembly.Browser.props</_WebAssemblyPropsFile>
-    <_WebAssemblyTargetsFile>$(MSBuildThisFileDirectory)\Microsoft.NET.Sdk.WebAssembly.Browser.targets</_WebAssemblyTargetsFile>
   </PropertyGroup>
 </Project>

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Pack.targets

@@ -9,4 +9,14 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
 Copyright (c) .NET Foundation. All rights reserved.
 ***********************************************************************************************
 -->
-<Project ToolsVersion="14.0"></Project>
+<Project ToolsVersion="14.0">
+ <PropertyGroup Condition="'$(RuntimeIdentifier)' == 'browser-wasm'">
+    <_WebAssemblyTargetsFile>$(MSBuildThisFileDirectory)\Microsoft.NET.Sdk.WebAssembly.Browser.targets</_WebAssemblyTargetsFile>
+  </PropertyGroup>
+
+  <!-- Library Mode defaults-->
+  <PropertyGroup Condition="'$(OutputType)' == 'Library'">
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
+  </PropertyGroup>
+</Project>

src/mono/nuget/mono-packages.proj

@@ -16,6 +16,7 @@
   <ItemGroup Condition="'$(TargetsWasi)' == 'true'">
     <ProjectReference Include="Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk\Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk.pkgproj" />
     <ProjectReference Include="..\wasm\templates\Microsoft.NET.Runtime.WebAssembly.Templates.csproj" />
+    <ProjectReference Include="Microsoft.NET.Sdk.WebAssembly.Pack\Microsoft.NET.Sdk.WebAssembly.Pack.pkgproj" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetsiOS)' == 'true' or '$(TargetsiOSSimulator)' == 'true'">

src/mono/wasi/Wasi.Build.Tests/WasiLibraryModeTests.cs

@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+using Xunit;
+using Xunit.Abstractions;
+using Xunit.Sdk;
+using Wasm.Build.Tests;
+
+#nullable enable
+
+namespace Wasi.Build.Tests;
+
+public class WasiLibraryModeTests : BuildTestBase
+{
+    public WasiLibraryModeTests(ITestOutputHelper output, SharedBuildPerTestClassFixture buildContext)
+        : base(output, buildContext)
+    {
+    }
+
+    [Fact]
+    public void ConsoleBuildLibraryMode()
+    {
+        string config = "Release";
+        string id = $"{config}_{GetRandomId()}";
+        string projectFile = CreateWasmTemplateProject(id, "wasiconsole");
+        string code =
+                """
+                using System;
+                using System.Runtime.InteropServices;
+                public unsafe class Test
+                {
+                    [UnmanagedCallersOnly(EntryPoint = "MyCallback")]
+                    public static int MyCallback()
+                    {
+                        Console.WriteLine("WASM Library MyCallback is called");
+                        return 100;
+                    }
+                }
+                """;
+        string csprojCode = 
+                """
+                <Project Sdk="Microsoft.NET.Sdk.WebAssembly">
+                    <PropertyGroup>
+                        <TargetFramework>net9.0</TargetFramework>
+                        <RuntimeIdentifier>wasi-wasm</RuntimeIdentifier>
+                        <WasmSingleFileBundle>true</WasmSingleFileBundle>
+                        <OutputType>Library</OutputType>
+                        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+                    </PropertyGroup>
+                </Project>
+                """;
+        File.WriteAllText(Path.Combine(_projectDir!, "Program.cs"), code);
+        File.WriteAllText(Path.Combine(_projectDir!, $"{id}.csproj"), csprojCode);
+        string projectName = Path.GetFileNameWithoutExtension(projectFile);
+        var buildArgs = new BuildArgs(projectName, config, AOT: false, ProjectFileContents: id, ExtraBuildArgs: null);
+        buildArgs = ExpandBuildArgs(buildArgs);
+        (_, string output) = BuildProject(buildArgs,
+                    id: id,
+                    new BuildProjectOptions(
+                        DotnetWasmFromRuntimePack: false,
+                        CreateProject: false,
+                        Publish: false,
+                        TargetFramework: BuildTestBase.DefaultTargetFramework
+                        ));
+
+        Assert.Contains("Build succeeded.", output);
+    }
+}

src/mono/wasi/build/WasiApp.targets

@@ -201,6 +201,7 @@
       <_WasmCommonCFlags Condition="'$(InvariantGlobalization)' == 'true'" Include="-DINVARIANT_GLOBALIZATION=1" />
       <_WasmCommonCFlags Condition="'$(InvariantTimezone)' == 'true'"      Include="-DINVARIANT_TIMEZONE=1" />
       <_WasmCommonCFlags Condition="'$(WasmLinkIcalls)' == 'true'"         Include="-DLINK_ICALLS=1" />
+      <_WasmCommonCFlags Condition="'$(_IsLibraryMode)' == 'true'"          Include="-DWASM_LIBRARY_MODE=1" />
       <_WasiClangCFlags Include="@(_WasmCommonCFlags)" />
 
       <_WasiClangCFlags Include="&quot;-I%(_WasmCommonIncludePaths.Identity)&quot;" />

src/mono/wasi/runtime/main.c

@@ -1,4 +1,5 @@
-#include <string.h>
+#include <stdbool.h>
+#include <string.h>
 #include <driver.h>
 #include <mono/metadata/assembly.h>
 
@@ -10,7 +11,40 @@ const char* dotnet_wasi_getentrypointassemblyname();
 WASI_AFTER_RUNTIME_LOADED_DECLARATIONS
 #endif
 
-int main(int argc, char * argv[]) {
+#ifdef WASM_LIBRARY_MODE
+// _initialize is a function generated by the WASI SDK libc that calls the LLVM synthesized __wasm_call_ctors function for reactor components:
+// https://github.com/WebAssembly/wasi-libc/blob/9f51a7102085ec6a6ced5778f0864c9af9f50000/libc-bottom-half/crt/crt1-reactor.c#L7-L27
+// We define and call it for WASM_LIBRARY_MODE and TARGET_WASI to call all the global c++ static constructors.  This ensures the runtime is initialized
+// when calling into WebAssembly Component Model components.
+extern void _initialize();
+
+// CustomNativeMain programs are built using the same libbootstrapperdll as WASM_LIBRARY_MODE but wasi-libc will not provide an _initialize implementation,
+// so create a dummy one here and make it weak to allow wasi-libc to provide the real implementation for WASI reactor components.
+__attribute__((weak)) void _initialize()
+{
+}
+
+// Guard the "_initialize" call so that well-behaving hosts do not get affected by this workaround.
+static bool g_CalledInitialize = false;
+
+__attribute__((constructor))
+void WasiInitializationFlag() {
+   *(volatile bool*)&g_CalledInitialize = true;
+}
+
+static bool runtime_initialized = false;
+
+#endif
+
+int initialize_runtime()
+{
+#if defined(WASM_LIBRARY_MODE)
+    if (runtime_initialized)
+		return 0;
+	if (!g_CalledInitialize)
+		_initialize();
+	runtime_initialized = true;
+#endif
 
 #ifndef WASM_SINGLE_FILE
 	mono_set_assemblies_path("managed");
@@ -21,7 +55,14 @@ int main(int argc, char * argv[]) {
 	// This is supplied from the MSBuild itemgroup @(WasiAfterRuntimeLoaded)
 	WASI_AFTER_RUNTIME_LOADED_CALLS
 #endif
-
+	return 0;
+}
+
+#ifndef WASM_LIBRARY_MODE
+int main(int argc, char * argv[]) {
+    int initval = initialize_runtime();
+    if (initval != 0)
+        return initval;
 	int arg_ofs = 0;
 #ifdef WASM_SINGLE_FILE
 	/*
@@ -71,3 +112,4 @@ int main(int argc, char * argv[]) {
 	}
 	return ret < 0 ? -ret : ret;
 }
+#endif

src/mono/wasi/wasi.proj

@@ -60,7 +60,8 @@
       Assemblies="@(WasmPInvokeAssembly)"
       PInvokeModules="@(WasmPInvokeModule)"
       PInvokeOutputPath="$(WasmPInvokeTablePath)"
-      InterpToNativeOutputPath="$(WasmInterpToNativeTablePath)">
+      InterpToNativeOutputPath="$(WasmInterpToNativeTablePath)"
+      IsLibraryMode="$(_IsLibraryMode)">
       <Output TaskParameter="FileWrites" ItemName="FileWrites" />
     </ManagedToNativeGenerator>
   </Target>

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

@@ -162,8 +162,9 @@
     </WasmLinkDotNetDependsOn>
 
     <WasmDedup Condition="'$(WasmDedup)' == ''">true</WasmDedup>
-    <IsWasiProject Condition="'$(IsWasiProject)' == '' and '$(RuntimeIdentifier)' == 'wasi-wasm' and '$(OutputType)' != 'Library'">true</IsWasiProject>
-    <IsBrowserWasmProject Condition="'$(IsBrowserWasmProject)' == '' and '$(RuntimeIdentifier)' == 'browser-wasm' and '$(OutputType)' != 'Library'">true</IsBrowserWasmProject>
+    <_IsLibraryMode Condition="'$(OutputType)' == 'Library' and '$(UsingMicrosoftNETSdkWebAssembly)' == 'true'">true</_IsLibraryMode>
+    <IsWasiProject Condition="'$(IsWasiProject)' == '' and '$(RuntimeIdentifier)' == 'wasi-wasm' and ('$(OutputType)' != 'Library' or '$(_IsLibraryMode)' == 'true')">true</IsWasiProject>
+    <IsBrowserWasmProject Condition="'$(IsBrowserWasmProject)' == '' and '$(RuntimeIdentifier)' == 'browser-wasm' and ('$(OutputType)' != 'Library' or '$(_IsLibraryMode)' == 'true')">true</IsBrowserWasmProject>
     <IsWasmProject Condition="'$(IsWasmProject)' == '' and ('$(IsWasiProject)' == 'true' or '$(IsBrowserWasmProject)' == 'true')">true</IsWasmProject>
     <WasmBuildAppAfterThisTarget Condition="'$(WasmBuildAppAfterThisTarget)' == '' and '$(DisableAutoWasmBuildApp)' != 'true'">Build</WasmBuildAppAfterThisTarget>
 
@@ -173,7 +174,7 @@
     <EnableDefaultWasmAssembliesToBundle Condition="'$(EnableDefaultWasmAssembliesToBundle)' == ''">true</EnableDefaultWasmAssembliesToBundle>
     <!-- VS uses DeployOnBuild, and sdk sets _IsPublishing -->
     <WasmBuildOnlyAfterPublish Condition="'$(WasmBuildOnlyAfterPublish)' == '' and ('$(DeployOnBuild)' == 'true' or '$(_IsPublishing)' == 'true')">true</WasmBuildOnlyAfterPublish>
-    <WasmGenerateAppBundle Condition="'$(WasmGenerateAppBundle)' == '' and '$(OutputType)' != 'Library'">true</WasmGenerateAppBundle>
+    <WasmGenerateAppBundle Condition="'$(WasmGenerateAppBundle)' == '' and ('$(OutputType)' != 'Library' or '$(_IsLibraryMode)' == 'true')">true</WasmGenerateAppBundle>
     <WasmGenerateAppBundle Condition="'$(WasmGenerateAppBundle)' == ''">false</WasmGenerateAppBundle>
 
     <!-- FIXME: can't set to true because
@@ -346,7 +347,7 @@
 
   <Target Name="_WasmGetRuntimeConfigPath">
     <PropertyGroup>
-      <_MainAssemblyPath Condition="'%(WasmAssembliesToBundle.FileName)' == $(AssemblyName) and '%(WasmAssembliesToBundle.Extension)' == '.dll' and $(WasmGenerateAppBundle) == 'true'">%(WasmAssembliesToBundle.Identity)</_MainAssemblyPath>
+      <_MainAssemblyPath Condition="'%(WasmAssembliesToBundle.FileName)' == '$(AssemblyName)' and '%(WasmAssembliesToBundle.Extension)' == '.dll' and $(WasmGenerateAppBundle) == 'true'">%(WasmAssembliesToBundle.Identity)</_MainAssemblyPath>
       <_WasmRuntimeConfigFilePath Condition="'$(_WasmRuntimeConfigFilePath)' == '' and $(_MainAssemblyPath) != ''">$([System.IO.Path]::ChangeExtension($(_MainAssemblyPath), '.runtimeconfig.json'))</_WasmRuntimeConfigFilePath>
       <_ParsedRuntimeConfigFilePath Condition="'$(_WasmRuntimeConfigFilePath)' != ''">$([System.IO.Path]::GetDirectoryName($(_WasmRuntimeConfigFilePath)))\runtimeconfig.bin</_ParsedRuntimeConfigFilePath>
     </PropertyGroup>
@@ -799,7 +800,8 @@
       PInvokeModules="@(_WasmPInvokeModules)"
       PInvokeOutputPath="$(_WasmPInvokeTablePath)"
       InterpToNativeOutputPath="$(_WasmInterpToNativeTablePath)"
-      CacheFilePath="$(_WasmM2NCachePath)">
+      CacheFilePath="$(_WasmM2NCachePath)"
+      IsLibraryMode="$(_IsLibraryMode)">
       <Output TaskParameter="FileWrites" ItemName="FileWrites" />
     </ManagedToNativeGenerator>
   </Target>

src/tasks/WasmAppBuilder/ManagedToNativeGenerator.cs

@@ -33,6 +33,8 @@ public class ManagedToNativeGenerator : Task
     public string? InterpToNativeOutputPath { get; set; }
     public string? CacheFilePath { get; set; }
 
+    public bool IsLibraryMode { get; set; }
+
     [Output]
     public string[]? FileWrites { get; private set; }
 
@@ -69,7 +71,7 @@ private void ExecuteInternal(LogAdapter log)
         List<string> managedAssemblies = FilterOutUnmanagedBinaries(Assemblies);
         if (ShouldRun(managedAssemblies))
         {
-            var pinvoke = new PInvokeTableGenerator(FixupSymbolName, log);
+            var pinvoke = new PInvokeTableGenerator(FixupSymbolName, log, IsLibraryMode);
             var icall = new IcallTableGenerator(RuntimeIcallTableFile, FixupSymbolName, log);
 
             var resolver = new PathAssemblyResolver(managedAssemblies);

src/tasks/WasmAppBuilder/PInvokeTableGenerator.cs

@@ -24,12 +24,14 @@ internal sealed class PInvokeTableGenerator
     private readonly List<PInvoke> pinvokes = new();
     private readonly List<PInvokeCallback> callbacks = new();
     private readonly PInvokeCollector _pinvokeCollector;
+    private readonly bool _isLibraryMode;
 
-    public PInvokeTableGenerator(Func<string, string> fixupSymbolName, LogAdapter log)
+    public PInvokeTableGenerator(Func<string, string> fixupSymbolName, LogAdapter log, bool isLibraryMode = false)
     {
         Log = log;
         _fixupSymbolName = fixupSymbolName;
         _pinvokeCollector = new(log);
+        _isLibraryMode = isLibraryMode;
     }
 
     public void ScanAssembly(Assembly asm)
@@ -379,6 +381,11 @@ private void EmitNativeToInterp(StreamWriter w, List<PInvokeCallback> callbacks)
             if (!is_void)
                 sb.Append($"  {MapType(method.ReturnType)} res;\n");
 
+            if (_isLibraryMode && HasAttribute(method, "System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute"))
+            {
+                sb.Append($"  initialize_runtime(); \n");
+            }
+
             // In case when null force interpreter to initialize the pointers
             sb.Append($"  if (!(WasmInterpEntrySig_{cb_index})wasm_native_to_interp_ftndescs [{cb_index}].func) {{\n");
             var assemblyFullName = cb.Method.DeclaringType == null ? "" : cb.Method.DeclaringType.Assembly.FullName;