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

eng/testing/tests.wasi.targets

@@ -7,6 +7,7 @@
 
     <WasmSingleFileBundle Condition="'$(WasmSingleFileBundle)' == ''">false</WasmSingleFileBundle>
     <WasmMainAssemblyFileName Condition="'$(WasmMainAssemblyFileName)' == ''">WasmTestRunner.dll</WasmMainAssemblyFileName>
+    <IsLibraryTest Condition="'$(OutputType)' == 'Library'">true</IsLibraryTest>
 
     <InstallWasmtimeForTests Condition="'$(InstallWasmtimeForTests)' == '' and
                                         ('$(ContinuousIntegrationBuild)' != 'true' or Exists('/.dockerenv'))"

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/sample/wasi/Directory.Build.targets

@@ -15,13 +15,13 @@
       TODOWASI - - tcplisten localhost:64000 - - env DEBUGGER_FD=4
     -->
     <Exec WorkingDirectory="bin/wasi-wasm/AppBundle"
-          Condition="'$(WasmBuildNative)' != 'true'"
+          Condition="'$(WasmBuildNative)' != 'true' and '$(OutputType)' != 'Library'"
           Command="$(WasmtimeDir)wasmtime$(_ExeExt) $(MONO_LOG_LEVEL) --dir . dotnet.wasm $(_SampleProjectName)" IgnoreExitCode="true" />
     <Exec WorkingDirectory="bin/wasi-wasm/AppBundle"
-          Condition="'$(WasmBuildNative)' == 'true' and '$(WasmSingleFileBundle)' != 'true'"
+          Condition="'$(WasmBuildNative)' == 'true' and '$(WasmSingleFileBundle)' != 'true' and '$(OutputType)' != 'Library'"
           Command="$(WasmtimeDir)wasmtime$(_ExeExt) $(MONO_LOG_LEVEL) --dir . dotnet.wasm" IgnoreExitCode="true" />
     <Exec WorkingDirectory="bin/wasi-wasm/AppBundle"
-          Condition="'$(WasmSingleFileBundle)' == 'true'"
+          Condition="'$(WasmSingleFileBundle)' == 'true' and '$(OutputType)' != 'Library'"
           Command="$(WasmtimeDir)wasmtime$(_ExeExt) $(MONO_LOG_LEVEL) $([System.IO.Path]::ChangeExtension($(_SampleAssembly), '.wasm'))" IgnoreExitCode="true" />
   </Target>
 

src/mono/sample/wasi/native/Program.cs

@@ -17,10 +17,17 @@ public static int MyExport(int number)
     [DllImport("*", EntryPoint = "UnmanagedFunc")]
     public static extern void MyImport(); // calls ManagedFunc aka MyExport
 
-    public unsafe static int Main(string[] args)
+    // public unsafe static int Main(string[] args)
+    // {
+    //     Console.WriteLine($"main: {args.Length}");
+    //     MyImport();
+    //     return 0;
+    // }
+
+    [UnmanagedCallersOnly(EntryPoint = "MyCallback")]
+    public static int MyCallback()
     {
-        Console.WriteLine($"main: {args.Length}");
-        MyImport();
-        return 0;
+        Console.WriteLine("WASM Library MyCallback is called");
+        return 100;
     }
 }

src/mono/sample/wasi/native/Wasi.Native.Sample.csproj

@@ -8,6 +8,11 @@
     <WasmNativeStrip>false</WasmNativeStrip>
     <IsBrowserWasmProject>false</IsBrowserWasmProject>
     <WasmSingleFileBundle>true</WasmSingleFileBundle>
+    <OutputType>Library</OutputType>
+    <!-- This is needed for ReferenceCopyLocalPaths to include RuntimePackAsset-->
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <!-- This is needed so it will not complain about WasmAssembliesToBundle is empty -->
+    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
   </PropertyGroup>
 
   <ItemGroup>

src/mono/sample/wasi/native/runtimeconfig.template.json

@@ -0,0 +1,10 @@
+{
+    "wasmHostProperties": {
+        "perHostConfig": [
+            {
+                "name": "wasmtime",
+                "Host": "wasmtime"
+            }
+        ]
+    }
+}

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="'$(WasmLinkIcalls)' == 'true'"         Include="-DLINK_ICALLS=1" />
+      <_WasmCommonCFlags Condition="'$(OutputType)' == 'Library' and '$(IsLibraryTest)' != '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 +11,31 @@ 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()
+{
+}
+
+static bool runtime_initialized = false;
+
+#endif
+
+int initialize_runtime()
+{
+#if defined(WASM_LIBRARY_MODE)
+    if (runtime_initialized)
+		return 0;
+    _initialize();
+	runtime_initialized = true;
+#endif
 
 #ifndef WASM_SINGLE_FILE
 	mono_set_assemblies_path("managed");
@@ -21,7 +46,14 @@ 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 +103,4 @@ int main(int argc, char * argv[]) {
 	}
 	return ret < 0 ? -ret : ret;
 }
+#endif

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

@@ -162,8 +162,8 @@
     </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 '$(OutputType)' != 'Library'">true</IsBrowserWasmProject>
+    <IsWasiProject Condition="'$(IsWasiProject)' == '' and '$(RuntimeIdentifier)' == 'wasi-wasm'">true</IsWasiProject>
+    <IsBrowserWasmProject Condition="'$(IsBrowserWasmProject)' == '' and '$(RuntimeIdentifier)' == 'browser-wasm'">true</IsBrowserWasmProject>
     <IsWasmProject Condition="'$(IsWasmProject)' == '' and ('$(IsWasiProject)' == 'true' or '$(IsBrowserWasmProject)' == 'true')">true</IsWasmProject>
     <WasmBuildAppAfterThisTarget Condition="'$(WasmBuildAppAfterThisTarget)' == '' and '$(DisableAutoWasmBuildApp)' != 'true'">Build</WasmBuildAppAfterThisTarget>
 
@@ -173,8 +173,7 @@
     <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="'$(WasmGenerateAppBundle)' == ''">false</WasmGenerateAppBundle>
+    <WasmGenerateAppBundle Condition="'$(WasmGenerateAppBundle)' == ''">true</WasmGenerateAppBundle>
 
     <!-- FIXME: can't set to true because
       /workspaces/runtime/.dotnet/sdk/7.0.100-rc.1.22431.12/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.FrameworkReferenceResolution.targets(135,5): error NETSDK1084: There is no application host available for the specified RuntimeIdentifier 'wasi-wasm'.
@@ -346,7 +345,7 @@
 
   <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>

src/tasks/WasmAppBuilder/PInvokeTableGenerator.cs

@@ -379,6 +379,13 @@ private void EmitNativeToInterp(StreamWriter w, List<PInvokeCallback> callbacks)
             if (!is_void)
                 sb.Append($"  {MapType(method.ReturnType)} res;\n");
 
+            if (HasAttribute(method, "System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute"))
+            {
+                sb.Append($"  #if defined(WASM_LIBRARY_MODE) \n");
+                sb.Append($"    initialize_runtime(); \n");
+                sb.Append($"  #endif\n");
+            }
+
             // In case when null force interpreter to initialize the pointers
             sb.Append($"  if (!(WasmInterpEntrySig_{cb_index})wasm_native_to_interp_ftndescs [{cb_index}].func) {{\n");
             var assemblyFullName = cb.Method.DeclaringType == null ? "" : cb.Method.DeclaringType.Assembly.FullName;