[mono][wasm] Force interpreter to initialize the pointers

src/mono/browser/runtime/runtime.c

@@ -76,6 +76,7 @@ int monoeg_g_setenv(const char *variable, const char *value, int overwrite);
 int32_t mini_parse_debug_option (const char *option);
 char *mono_method_get_full_name (MonoMethod *method);
 void mono_trace_init (void);
+MonoMethod *mono_marshal_get_managed_wrapper (MonoMethod *method, MonoClass *delegate_klass, MonoGCHandle target_handle, MonoError *error);
 
 /* Not part of public headers */
 #define MONO_ICALL_TABLE_CALLBACKS_VERSION 3
@@ -356,3 +357,25 @@ mono_wasm_assembly_find_method (MonoClass *klass, const char *name, int argument
 	MONO_EXIT_GC_UNSAFE;
 	return result;
 }
+
+/*
+ * mono_wasm_marshal_get_managed_wrapper:
+ * Creates a wrapper for a function pointer to a method marked with
+ * UnamangedCallersOnlyAttribute.
+ * This wrapper ensures that the interpreter initializes the pointers.
+ */
+void
+mono_wasm_marshal_get_managed_wrapper (const char* assemblyName, const char* nspace, const char* typeName, const char* methodName, int num_params)
+{
+	MonoError error;
+	mono_error_init (&error);
+	MonoAssembly* assembly = mono_wasm_assembly_load (assemblyName);
+	assert (assembly);
+	MonoClass* class = mono_wasm_assembly_find_class (assembly, nspace, typeName);
+	assert (class);
+	MonoMethod* method = mono_wasm_assembly_find_method (class, methodName, num_params);
+	assert (method);
+	MonoMethod *managedWrapper = mono_marshal_get_managed_wrapper (method, NULL, 0, &error);
+	assert (managedWrapper);
+	mono_compile_method (managedWrapper);
+}

src/mono/browser/runtime/runtime.h

@@ -18,5 +18,7 @@ extern int mono_wasm_enable_gc;
 MonoDomain *mono_wasm_load_runtime_common (int debug_level, MonoLogCallback log_callback, const char *interp_opts);
 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* nspace, const char* typeName, const char* methodName, int num_params);
 
 #endif

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

@@ -20,11 +20,6 @@ public static int MyExport(int number)
     public unsafe static int Main(string[] args)
     {
         Console.WriteLine($"main: {args.Length}");
-        // workaround to force the interpreter to initialize wasm_native_to_interp_ftndesc for MyExport
-        if (args.Length > 10000) {
-            ((IntPtr)(delegate* unmanaged<int,int>)&MyExport).ToString();
-        }
-
         MyImport();
         return 0;
     }

src/tasks/WasmAppBuilder/PInvokeTableGenerator.cs

@@ -323,6 +323,14 @@ private void EmitNativeToInterp(StreamWriter w, List<PInvokeCallback> callbacks)
         // Only blittable parameter/return types are supposed.
         int cb_index = 0;
 
+        w.Write(@"#include <mono/utils/details/mono-error-types.h>
+                #include <mono/metadata/assembly.h>
+                #include <mono/utils/mono-error.h>
+                #include <mono/metadata/object.h>
+                #include <mono/utils/details/mono-logger-types.h>
+                #include ""runtime.h""
+                ");
+
         // Arguments to interp entry functions in the runtime
         w.WriteLine($"InterpFtnDesc wasm_native_to_interp_ftndescs[{callbacks.Count}] = {{}};");
 
@@ -371,7 +379,16 @@ private void EmitNativeToInterp(StreamWriter w, List<PInvokeCallback> callbacks)
             if (!is_void)
                 sb.Append($"  {MapType(method.ReturnType)} res;\n");
 
-            //sb.Append($"  printf(\"{entry_name} called\\n\");\n");
+            // In case when null force interpreter to initialize the pointers
+            sb.Append($"  if (!(WasmInterpEntrySig_{cb_index})wasm_native_to_interp_ftndescs [{cb_index}].func) {{\n");
+            var assemblyFullName = cb.Method.DeclaringType == null ? "" : cb.Method.DeclaringType.Assembly.FullName;
+            var assemblyName = assemblyFullName != null && assemblyFullName.Split(',').Length > 0 ? assemblyFullName.Split(',')[0].Trim() : "";
+            var typeName = cb.Method.DeclaringType == null  || cb.Method.DeclaringType.FullName == null ? "" : cb.Method.DeclaringType.FullName;
+            var methodName = cb.Method.Name;
+            int numParams = method.GetParameters().Length;
+            sb.Append($"   mono_wasm_marshal_get_managed_wrapper (\"{assemblyName}\", \"{string.Empty}\", \"{typeName}\", \"{methodName}\", {numParams});\n");
+            sb.Append($"  }}\n");
+
             sb.Append($"  ((WasmInterpEntrySig_{cb_index})wasm_native_to_interp_ftndescs [{cb_index}].func) (");
             if (!is_void)
             {