diff --git a/examples/interpret.rs b/examples/interpret.rs
index 7111f36..f43648d 100644
--- a/examples/interpret.rs
+++ b/examples/interpret.rs
@@ -16,5 +16,5 @@ fn main() {
     let module = parity_wasm::deserialize_file(&args[1]).expect("Failed to load module");
     let module = program.add_module("main", module).expect("Failed to initialize module");
     let argument: i32 = args[2].parse().expect("Integer argument required");
-    println!("Result: {:?}", module.execute_export("_call", vec![parity_wasm::RuntimeValue::I32(argument)]));
+    println!("Result: {:?}", module.execute_export("_call", vec![parity_wasm::RuntimeValue::I32(argument)].into()));
 }
diff --git a/src/interpreter/env.rs b/src/interpreter/env.rs
index 861b06e..9535445 100644
--- a/src/interpreter/env.rs
+++ b/src/interpreter/env.rs
@@ -1,11 +1,12 @@
 use std::sync::{Arc, Weak};
-use std::collections::HashMap;
 
-use builder::{module, function, export};
+use builder::module;
 use elements::{Module, FunctionType, ExportEntry, Internal, GlobalEntry, GlobalType,
 	ValueType, InitExpr, Opcode, Opcodes};
 use interpreter::Error;
-use interpreter::module::{ModuleInstanceInterface, ModuleInstance, ItemIndex, CallerContext};
+use interpreter::env_native::NATIVE_INDEX_FUNC_MIN;
+use interpreter::module::{ModuleInstanceInterface, ModuleInstance, ExecutionParams,
+	ItemIndex, CallerContext};
 use interpreter::memory::{MemoryInstance, LINEAR_MEMORY_PAGE_SIZE};
 use interpreter::table::TableInstance;
 use interpreter::value::{RuntimeValue, TransmuteInto};
@@ -58,44 +59,10 @@ const INDEX_FUNC_ASSERT: u32 = 1;
 const INDEX_FUNC_ENLARGE_MEMORY: u32 = 2;
 /// Index of getTotalMemory function.
 const INDEX_FUNC_GET_TOTAL_MEMORY: u32 = 3;
-/// Index of abortOnCannotGrowMemory function.
-/*const INDEX_FUNC_ABORT_ON_CANNOT_GROW_MEMORY: u32 = 4;
-/// Index of invoke_vi function.
-const INDEX_FUNC_INVOKE_VI: u32 = 5;
-/// Index of invoke function.
-const INDEX_FUNC_INVOKE: u32 = 6;*/
 /// Min index of reserver function.
-const INDEX_FUNC_MIN_NONUSED: u32 = 7;
+const INDEX_FUNC_MIN_NONUSED: u32 = 4;
 /// Max index of reserved function.
-const INDEX_FUNC_MAX: u32 = 10000;
-
-/// Set of user-defined functions
-pub type UserFunctions = HashMap<String, UserFunction>;
-
-/// User function closure
-pub type UserFunctionClosure = Box<UserFunctionInterface>;
-
-/// User-defined function execution interface
-pub trait UserFunctionInterface {
-	/// Handles the user function invocation
-	fn call(&mut self, module: &ModuleInstance, context: CallerContext) -> Result<Option<RuntimeValue>, Error>; 
-}
-
-impl<T> UserFunctionInterface for T where T: FnMut(&ModuleInstance, CallerContext) -> Result<Option<RuntimeValue>, Error> {
-    fn call(&mut self, module: &ModuleInstance, context: CallerContext) -> Result<Option<RuntimeValue>, Error> {
-        (&mut *self)(module, context)
-    }
-}
-
-/// Signature of user-defined env function
-pub struct UserFunction {
-	/// User function parameters (for signature matching)
-	pub params: Vec<ValueType>,
-	/// User function return type (for signature matching)
-	pub result: Option<ValueType>,
-	/// Executor of the function
-	pub closure: UserFunctionClosure,
-}
+const INDEX_FUNC_MAX: u32 = NATIVE_INDEX_FUNC_MIN - 1;
 
 /// Environment parameters.
 pub struct EnvParams {
@@ -107,41 +74,37 @@ pub struct EnvParams {
 	pub allow_memory_growth: bool,
 }
 
-type UserFunctionsInternals = Vec<::std::cell::RefCell<UserFunctionClosure>>;
-
 pub struct EnvModuleInstance {
 	_params: EnvParams,
-	user_functions: UserFunctionsInternals,
 	instance: ModuleInstance,
 }
 
 impl EnvModuleInstance {
-	pub fn new(params: EnvParams, user_functions: UserFunctionsInternals, module: Module) -> Result<Self, Error> {
+	pub fn new(params: EnvParams, module: Module) -> Result<Self, Error> {
 		let instance = ModuleInstance::new(Weak::default(), module)?;
 
 		Ok(EnvModuleInstance {
 			_params: params,
-			user_functions: user_functions,
 			instance: instance,
 		})
 	}
 }
 
 impl ModuleInstanceInterface for EnvModuleInstance {
-	fn execute_main(&self, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
-		self.instance.execute_main(args)
+	fn execute_main(&self, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.instance.execute_main(params)
 	}
 
-	fn execute_index(&self, index: u32, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
-		self.instance.execute_index(index, args)
+	fn execute_index(&self, index: u32, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.instance.execute_index(index, params)
 	}
 
-	fn execute_export(&self, name: &str, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
-		self.instance.execute_export(name, args)
+	fn execute_export(&self, name: &str, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.instance.execute_export(name, params)
 	}
 
-	fn module(&self) -> &Module {
-		self.instance.module()
+	fn export_entry(&self, name: &str) -> Result<Internal, Error> {
+		self.instance.export_entry(name)
 	}
 
 	fn table(&self, index: ItemIndex) -> Result<Arc<TableInstance>, Error> {
@@ -165,6 +128,7 @@ impl ModuleInstanceInterface for EnvModuleInstance {
 	}
 
 	fn call_internal_function(&self, outer: CallerContext, index: u32, _function_type: Option<&FunctionType>) -> Result<Option<RuntimeValue>, Error> {
+		// TODO: check function type
 		// to make interpreter independent of *SCRIPTEN runtime, just make abort/assert = interpreter Error
 		match index {
 			INDEX_FUNC_ABORT => self.global(ItemIndex::IndexSpace(INDEX_GLOBAL_ABORT))
@@ -183,26 +147,17 @@ impl ModuleInstanceInterface for EnvModuleInstance {
 				.map(|g| g.get())
 				.map(Some),
 			INDEX_FUNC_MIN_NONUSED ... INDEX_FUNC_MAX => Err(Error::Trap("unimplemented".into())),
-			idx if idx > INDEX_FUNC_MAX && idx <= INDEX_FUNC_MAX + self.user_functions.len() as u32 => {
-				// user-defined function
-				let user_index = idx - (INDEX_FUNC_MAX+1);
-				let func = self.user_functions.get(user_index as usize).ok_or(Error::Trap(format!("Trying to invoke user-defined function {}", user_index)))?;
-				func.borrow_mut().call(&self.instance, outer)
-			},
-			// idx @ _ if idx == INDEX_FUNC_MAX + 1 => outer.value_stack.pop().map(|_| None), // TODO: `gas(i32) -> None` function
-			// idx @ _ if idx == INDEX_FUNC_MAX + 2 => Ok(Some(RuntimeValue::I32(0))), // TODO: `_storage_size() -> i32` function
-			// idx @ _ if idx == INDEX_FUNC_MAX + 3 => outer.value_stack.pop_triple().map(|_| Some(RuntimeValue::I32(0))), // TODO: `_storage_size(i32,i32,i32) -> i32` function
 			_ => Err(Error::Trap(format!("trying to call function with index {} in env module", index))),
 		}
 	}
 }
 
-pub fn env_module(user_functions: UserFunctions) -> Result<EnvModuleInstance, Error> {
+pub fn env_module() -> Result<EnvModuleInstance, Error> {
 	let env_params = EnvParams::default();
 	debug_assert!(env_params.total_stack < env_params.total_memory);
 	debug_assert!((env_params.total_stack % LINEAR_MEMORY_PAGE_SIZE) == 0);
 	debug_assert!((env_params.total_memory % LINEAR_MEMORY_PAGE_SIZE) == 0);
-	let mut builder = module()
+	let builder = module()
 		// memory regions
 		.memory()
 			.with_min(env_params.total_memory / LINEAR_MEMORY_PAGE_SIZE)
@@ -255,29 +210,7 @@ pub fn env_module(user_functions: UserFunctions) -> Result<EnvModuleInstance, Er
 			.build()
 			.with_export(ExportEntry::new("getTotalMemory".into(), Internal::Function(INDEX_FUNC_GET_TOTAL_MEMORY)));
 
-	let mut funcs = user_functions;
-	let mut internals = UserFunctionsInternals::new();
-	let mut index = INDEX_FUNC_MAX + 1;
-	for (func_name, func) in funcs.drain() {
-		let _location = builder.push_function(
-			function()
-				.signature().with_params(func.params).with_return_type(func.result).build()
-				.build()
-		);
-
-		let _export_idx = builder.push_export(
-			export()
-				.field(&func_name)
-				.internal().func(index)
-				.build()
-		);
-
-		internals.push(::std::cell::RefCell::new(func.closure));
-
-		index += 1;
-	}
-
-	EnvModuleInstance::new(env_params, internals, builder.build())
+	EnvModuleInstance::new(env_params, builder.build())
 }
 
 impl Default for EnvParams {
diff --git a/src/interpreter/env_native.rs b/src/interpreter/env_native.rs
new file mode 100644
index 0000000..09e5227
--- /dev/null
+++ b/src/interpreter/env_native.rs
@@ -0,0 +1,124 @@
+use std::sync::Arc;
+use std::collections::HashMap;
+use parking_lot::RwLock;
+use elements::{FunctionType, Internal, ValueType};
+use interpreter::Error;
+use interpreter::module::{ModuleInstanceInterface, ExecutionParams, ItemIndex,
+	CallerContext};
+use interpreter::memory::MemoryInstance;
+use interpreter::table::TableInstance;
+use interpreter::value::RuntimeValue;
+use interpreter::variable::VariableInstance;
+
+/// Min index of native function.
+pub const NATIVE_INDEX_FUNC_MIN: u32 = 10001;
+
+/// User function closure type.
+// pub type UserFunctionClosure<'a> = &'a mut FnMut(context: CallerContext) -> Result<Option<RuntimeValue>, Error>;
+
+/// User functions executor.
+pub trait UserFunctionExecutor {
+	/// Execute function with given name.
+	fn execute(&mut self, name: &str, context: CallerContext) -> Result<Option<RuntimeValue>, Error>;
+}
+
+/// User function type.
+pub struct UserFunction {
+	/// User function name.
+	pub name: String,
+	/// User function parameters (for signature matching).
+	pub params: Vec<ValueType>,
+	/// User function return type (for signature matching).
+	pub result: Option<ValueType>,
+}
+
+/// Set of user-defined functions
+pub struct UserFunctions<'a> {
+	/// Functions list.
+	pub functions: Vec<UserFunction>,
+	/// Functions executor.
+	pub executor: &'a mut UserFunctionExecutor,
+}
+
+/// Native module instance.
+pub struct NativeModuleInstance<'a> {
+	/// Underllying module reference.
+	env: Arc<ModuleInstanceInterface>,
+	/// User function executor.
+	executor: RwLock<&'a mut UserFunctionExecutor>,
+	/// By-name functions index.
+	by_name: HashMap<String, u32>,
+	/// User functions list.
+	functions: Vec<UserFunction>,
+}
+
+impl<'a> NativeModuleInstance<'a> {
+	/// Create new native module
+	pub fn new(env: Arc<ModuleInstanceInterface>, functions: UserFunctions<'a>) -> Result<Self, Error> {
+		Ok(NativeModuleInstance {
+			env: env,
+			executor: RwLock::new(functions.executor),
+			by_name: functions.functions.iter().enumerate().map(|(i, f)| (f.name.clone(), i as u32)).collect(),
+			functions: functions.functions,
+		})
+	}
+}
+
+impl<'a> ModuleInstanceInterface for NativeModuleInstance<'a> {
+	fn execute_main(&self, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.env.execute_main(params)
+	}
+
+	fn execute_index(&self, index: u32, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.env.execute_index(index, params)
+	}
+
+	fn execute_export(&self, name: &str, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		self.env.execute_export(name, params)
+	}
+
+	fn export_entry(&self, name: &str) -> Result<Internal, Error> {
+		if let Some(index) = self.by_name.get(name) {
+			return Ok(Internal::Function(NATIVE_INDEX_FUNC_MIN + *index));
+		}
+
+		self.env.export_entry(name)
+	}
+
+	fn table(&self, index: ItemIndex) -> Result<Arc<TableInstance>, Error> {
+		self.env.table(index)
+	}
+
+	fn memory(&self, index: ItemIndex) -> Result<Arc<MemoryInstance>, Error> {
+		self.env.memory(index)
+	}
+
+	fn global(&self, index: ItemIndex) -> Result<Arc<VariableInstance>, Error> {
+		self.env.global(index)
+	}
+
+	fn call_function(&self, outer: CallerContext, index: ItemIndex) -> Result<Option<RuntimeValue>, Error> {
+		self.env.call_function(outer, index)
+	}
+
+	fn call_function_indirect(&self, outer: CallerContext, table_index: ItemIndex, type_index: u32, func_index: u32) -> Result<Option<RuntimeValue>, Error> {
+		self.env.call_function_indirect(outer, table_index, type_index, func_index)
+	}
+
+	fn call_internal_function(&self, outer: CallerContext, index: u32, function_type: Option<&FunctionType>) -> Result<Option<RuntimeValue>, Error> {
+		if index < NATIVE_INDEX_FUNC_MIN {
+			return self.env.call_internal_function(outer, index, function_type);
+		}
+
+		// TODO: check type
+		self.functions
+			.get((index - NATIVE_INDEX_FUNC_MIN) as usize)
+			.ok_or(Error::Native(format!("trying to call native function with index {}", index)))
+			.and_then(|f| self.executor.write().execute(&f.name, outer))
+	}
+}
+
+/// Create wrapper for env module with given native user functions.
+pub fn env_native_module(env: Arc<ModuleInstanceInterface>, user_functions: UserFunctions) -> Result<NativeModuleInstance, Error> {
+	NativeModuleInstance::new(env, user_functions)
+}
diff --git a/src/interpreter/imports.rs b/src/interpreter/imports.rs
index 9cf8574..6588a6b 100644
--- a/src/interpreter/imports.rs
+++ b/src/interpreter/imports.rs
@@ -1,4 +1,5 @@
 use std::sync::{Arc, Weak};
+use std::collections::HashMap;
 use elements::{ImportSection, ImportEntry, External, Internal};
 use interpreter::Error;
 use interpreter::memory::MemoryInstance;
@@ -94,7 +95,13 @@ impl ModuleImports {
 	}
 
 	/// Get module reference.
-	pub fn module(&self, name: &str) -> Result<Arc<ModuleInstanceInterface>, Error> {
+	pub fn module<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, name: &str) -> Result<Arc<ModuleInstanceInterface + 'a>, Error> {
+		if let Some(externals) = externals {
+			if let Some(module) = externals.get(name).cloned() {
+				return Ok(module);
+			}
+		}
+
 		self.program
 			.upgrade()
 			.ok_or(Error::Program("program unloaded".into()))
@@ -102,8 +109,8 @@ impl ModuleImports {
 	}
 
 	/// Get function index.
-	pub fn function(&self, import: &ImportEntry) -> Result<u32, Error> {
-		let (_, export) = self.external_export(import)?;
+	pub fn function<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, import: &ImportEntry) -> Result<u32, Error> {
+		let (_, export) = self.external_export(externals, import)?;
 		if let Internal::Function(external_index) = export {
 			return Ok(external_index);
 		}
@@ -112,8 +119,8 @@ impl ModuleImports {
 	}
 
 	/// Get table reference.
-	pub fn table(&self, import: &ImportEntry) -> Result<Arc<TableInstance>, Error> {
-		let (module, export) = self.external_export(import)?;
+	pub fn table<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, import: &ImportEntry) -> Result<Arc<TableInstance>, Error> {
+		let (module, export) = self.external_export(externals, import)?;
 		if let Internal::Table(external_index) = export {
 			return module.table(ItemIndex::Internal(external_index));
 		}
@@ -122,8 +129,8 @@ impl ModuleImports {
 	}
 
 	/// Get memory reference.
-	pub fn memory(&self, import: &ImportEntry) -> Result<Arc<MemoryInstance>, Error> {
-		let (module, export) = self.external_export(import)?;
+	pub fn memory<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, import: &ImportEntry) -> Result<Arc<MemoryInstance>, Error> {
+		let (module, export) = self.external_export(externals, import)?;
 		if let Internal::Memory(external_index) = export {
 			return module.memory(ItemIndex::Internal(external_index));
 		}
@@ -132,8 +139,8 @@ impl ModuleImports {
 	}
 
 	/// Get global reference.
-	pub fn global(&self, import: &ImportEntry) -> Result<Arc<VariableInstance>, Error> {
-		let (module, export) = self.external_export(import)?;
+	pub fn global<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, import: &ImportEntry) -> Result<Arc<VariableInstance>, Error> {
+		let (module, export) = self.external_export(externals, import)?;
 		if let Internal::Global(external_index) = export {
 			return module.global(ItemIndex::Internal(external_index));
 		}
@@ -141,14 +148,10 @@ impl ModuleImports {
 		Err(Error::Program(format!("wrong import {} from module {} (expecting global)", import.field(), import.module())))
 	}
 
-	fn external_export(&self, import: &ImportEntry) -> Result<(Arc<ModuleInstanceInterface>, Internal), Error> {
-		self.module(import.module())
-			.and_then(|m| m.module().export_section()
-				.ok_or(Error::Program(format!("trying to import from module {} without export section", import.module())))
-				.and_then(|s| s.entries().iter()
-					.find(|e| e.field() == import.field())
-					.map(|e| e.internal())
-					.ok_or(Error::Program(format!("unresolved import {} from module {}", import.field(), import.module())))
-				.map(|export| (m.clone(), *export))))
+	fn external_export<'a>(&self, externals: Option<&'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>>, import: &ImportEntry) -> Result<(Arc<ModuleInstanceInterface + 'a>, Internal), Error> {
+		self.module(externals, import.module())
+			.and_then(|m|
+				m.export_entry(import.field())
+					.map(|e| (m, e)))
 	}
 }
diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 3d8fcc0..d436a3e 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -27,6 +27,8 @@ pub enum Error {
 	Interpreter(String),
 	/// Env module error.
 	Env(String),
+	/// Native module error.
+	Native(String),
 	/// Trap.
 	Trap(String),
 }
@@ -46,12 +48,14 @@ impl Into<String> for Error {
 			Error::Interpreter(s) => s,
 			Error::Value(s) => s,
 			Error::Env(s) => s,
+			Error::Native(s) => s,
 			Error::Trap(s) => format!("trap: {}", s),
 		}
 	}
 }
 
 mod env;
+mod env_native;
 mod imports;
 mod memory;
 mod module;
@@ -65,7 +69,10 @@ mod variable;
 #[cfg(test)]
 mod tests;
 
-pub use self::module::{ModuleInstance, ModuleInstanceInterface, ItemIndex, CallerContext};
+pub use self::memory::MemoryInstance;
+pub use self::module::{ModuleInstance, ModuleInstanceInterface, ItemIndex, CallerContext, ExecutionParams};
+pub use self::table::TableInstance;
 pub use self::program::ProgramInstance;
 pub use self::value::RuntimeValue;
-pub use self::env::{UserFunctions, UserFunction, UserFunctionInterface};
\ No newline at end of file
+pub use self::variable::VariableInstance;
+pub use self::env_native::{env_native_module, UserFunctions, UserFunction, UserFunctionExecutor};
diff --git a/src/interpreter/module.rs b/src/interpreter/module.rs
index b195eaf..7e987be 100644
--- a/src/interpreter/module.rs
+++ b/src/interpreter/module.rs
@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::iter::repeat;
 use std::sync::{Arc, Weak};
 use elements::{Module, InitExpr, Opcode, Type, FunctionType, FuncBody, Internal};
@@ -11,16 +12,25 @@ use interpreter::table::TableInstance;
 use interpreter::value::{RuntimeValue, TryInto, TransmuteInto};
 use interpreter::variable::{VariableInstance, VariableType};
 
+#[derive(Default, Clone)]
+/// Execution context.
+pub struct ExecutionParams<'a> {
+	/// Arguments.
+	pub args: Vec<RuntimeValue>,
+	/// Execution-local external modules.
+	pub externals: HashMap<String, Arc<ModuleInstanceInterface + 'a>>,
+}
+
 /// Module instance API.
 pub trait ModuleInstanceInterface {
 	/// Execute start function of the module.
-	fn execute_main(&self, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error>;
+	fn execute_main(&self, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error>;
 	/// Execute function with the given index.
-	fn execute_index(&self, index: u32, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error>;
+	fn execute_index(&self, index: u32, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error>;
 	/// Execute function with the given export name.
-	fn execute_export(&self, name: &str, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error>;
-	/// Get module description reference.
-	fn module(&self) -> &Module;
+	fn execute_export(&self, name: &str, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error>;
+	/// Get export entry.
+	fn export_entry(&self, name: &str) -> Result<Internal, Error>;
 	/// Get table reference.
 	fn table(&self, index: ItemIndex) -> Result<Arc<TableInstance>, Error>;
 	/// Get memory reference.
@@ -42,7 +52,7 @@ pub enum ItemIndex {
 	IndexSpace(u32),
 	/// Internal item index (i.e. index of item in items section).
 	Internal(u32),
-	/// External item index (i.e. index of item in the import section).
+	/// External module item index (i.e. index of item in the import section).
 	External(u32),
 }
 
@@ -68,6 +78,35 @@ pub struct CallerContext<'a> {
 	pub frame_stack_limit: usize,
 	/// Stack of the input parameters
 	pub value_stack: &'a mut StackWithLimit<RuntimeValue>,
+	/// Execution-local external modules.
+	pub externals: &'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>,
+}
+
+impl<'a> ExecutionParams<'a> {
+	/// Create new execution params with given externa; module override.
+	pub fn with_external(name: String, module: Arc<ModuleInstanceInterface + 'a>) -> Self {
+		let mut externals = HashMap::new();
+		externals.insert(name, module);
+		ExecutionParams {
+			args: Vec::new(),
+			externals: externals,
+		}
+	}
+
+	/// Add argument.
+	pub fn add_argument(mut self, arg: RuntimeValue) -> Self {
+		self.args.push(arg);
+		self
+	}
+}
+
+impl<'a> From<Vec<RuntimeValue>> for ExecutionParams<'a> {
+	fn from(args: Vec<RuntimeValue>) -> ExecutionParams<'a> {
+		ExecutionParams {
+			args: args,
+			externals: HashMap::new(),
+		}
+	}
 }
 
 impl ModuleInstance {
@@ -149,19 +188,19 @@ impl ModuleInstance {
 }
 
 impl ModuleInstanceInterface for ModuleInstance {
-	fn execute_main(&self, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
+	fn execute_main(&self, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
 		let index = self.module.start_section().ok_or(Error::Program("module has no start section".into()))?;
-		self.execute_index(index, args)
+		self.execute_index(index, params)
 	}
 
-	fn execute_index(&self, index: u32, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
-		let args_len = args.len();
-		let mut args = StackWithLimit::with_data(args, args_len);
-		let caller_context = CallerContext::topmost(&mut args);
+	fn execute_index(&self, index: u32, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
+		let args_len = params.args.len();
+		let mut args = StackWithLimit::with_data(params.args, args_len);
+		let caller_context = CallerContext::topmost(&mut args, &params.externals);
 		self.call_function(caller_context, ItemIndex::IndexSpace(index))
 	}
 
-	fn execute_export(&self, name: &str, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
+	fn execute_export(&self, name: &str, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
 		let index = self.module.export_section()
 			.ok_or(Error::Function("missing export section".into()))
 			.and_then(|s| s.entries().iter()
@@ -175,11 +214,16 @@ impl ModuleInstanceInterface for ModuleInstance {
 					_ => unreachable!(), // checked couple of lines above
 				})
 			)?;
-		self.execute_index(index, args)
+		self.execute_index(index, params)
 	}
 
-	fn module(&self) -> &Module {
-		&self.module
+	fn export_entry(&self, name: &str) -> Result<Internal, Error> {
+		self.module.export_section()
+			.ok_or(Error::Program(format!("trying to import {} from module without export section", name)))
+			.and_then(|s| s.entries().iter()
+				.find(|e| e.field() == name)
+				.map(|e| *e.internal())
+				.ok_or(Error::Program(format!("unresolved import {}", name))))
 	}
 
 	fn table(&self, index: ItemIndex) -> Result<Arc<TableInstance>, Error> {
@@ -191,7 +235,7 @@ impl ModuleInstanceInterface for ModuleInstance {
 				.ok_or(Error::Table(format!("trying to access external table with index {} in module without import section", index)))
 				.and_then(|s| s.entries().get(index as usize)
 					.ok_or(Error::Table(format!("trying to access external table with index {} in module with {}-entries import section", index, s.entries().len()))))
-				.and_then(|e| self.imports.table(e)),
+				.and_then(|e| self.imports.table(None, e)),
 		}
 	}
 
@@ -204,7 +248,7 @@ impl ModuleInstanceInterface for ModuleInstance {
 				.ok_or(Error::Memory(format!("trying to access external memory with index {} in module without import section", index)))
 				.and_then(|s| s.entries().get(index as usize)
 					.ok_or(Error::Memory(format!("trying to access external memory with index {} in module with {}-entries import section", index, s.entries().len()))))
-				.and_then(|e| self.imports.memory(e)),
+				.and_then(|e| self.imports.memory(None, e)),
 		}
 	}
 
@@ -217,7 +261,7 @@ impl ModuleInstanceInterface for ModuleInstance {
 				.ok_or(Error::Global(format!("trying to access external global with index {} in module without import section", index)))
 				.and_then(|s| s.entries().get(index as usize)
 					.ok_or(Error::Global(format!("trying to access external global with index {} in module with {}-entries import section", index, s.entries().len()))))
-				.and_then(|e| self.imports.global(e)),
+				.and_then(|e| self.imports.global(None, e)),
 		}
 	}
 
@@ -230,7 +274,7 @@ impl ModuleInstanceInterface for ModuleInstance {
 				.ok_or(Error::Function(format!("trying to access external function with index {} in module without import section", index)))
 				.and_then(|s| s.entries().get(index as usize)
 					.ok_or(Error::Function(format!("trying to access external function with index {} in module with {}-entries import section", index, s.entries().len()))))
-				.and_then(|e| Ok((self.imports.module(e.module())?, self.imports.function(e)?)))
+				.and_then(|e| Ok((self.imports.module(Some(outer.externals), e.module())?, self.imports.function(Some(outer.externals), e)?)))
 				.and_then(|(m, index)| m.call_internal_function(outer, index, None)),
 		}
 	}
@@ -263,13 +307,13 @@ impl ModuleInstanceInterface for ModuleInstance {
 					.ok_or(Error::Function(format!("trying to access external table with index {} in module without import section", table_index)))
 					.and_then(|s| s.entries().get(table_index as usize)
 						.ok_or(Error::Function(format!("trying to access external table with index {} in module with {}-entries import section", table_index, s.entries().len()))))
-					.and_then(|e| self.imports.module(e.module()))?;
+					.and_then(|e| self.imports.module(Some(outer.externals), e.module()))?;
 				module.call_internal_function(outer, index, Some(function_type))
 			}
 		}
 	}
 
-	fn call_internal_function(&self, outer: CallerContext, index: u32, function_type: Option<&FunctionType>) -> Result<Option<RuntimeValue>, Error> {
+	fn call_internal_function(&self, mut outer: CallerContext, index: u32, function_type: Option<&FunctionType>) -> Result<Option<RuntimeValue>, Error> {
 		// TODO: cache
 		// internal index = index of function in functions section && index of code in code section
 		// get function type index
@@ -311,19 +355,20 @@ impl ModuleInstanceInterface for ModuleInstance {
 		let function_code = function_body.code().elements();
 		let value_stack_limit = outer.value_stack_limit;
 		let frame_stack_limit = outer.frame_stack_limit;
-		let locals = prepare_function_locals(actual_function_type, function_body, outer)?;
-		let mut innner = FunctionContext::new(self, value_stack_limit, frame_stack_limit, actual_function_type, function_code, locals)?;
+		let locals = prepare_function_locals(actual_function_type, function_body, &mut outer)?;
+		let mut innner = FunctionContext::new(self, outer.externals, value_stack_limit, frame_stack_limit, actual_function_type, function_code, locals)?;
 		Interpreter::run_function(&mut innner, function_code)
 	}
 }
 
 impl<'a> CallerContext<'a> {
 	/// Top most args
-	pub fn topmost(args: &'a mut StackWithLimit<RuntimeValue>) -> Self {
+	pub fn topmost(args: &'a mut StackWithLimit<RuntimeValue>, externals: &'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>) -> Self {
 		CallerContext {
 			value_stack_limit: 1024,
 			frame_stack_limit: 1024,
 			value_stack: args,
+			externals: externals,
 		}
 	}
 
@@ -332,12 +377,13 @@ impl<'a> CallerContext<'a> {
 		CallerContext {
 			value_stack_limit: outer.value_stack().limit() - outer.value_stack().len(),
 			frame_stack_limit: outer.frame_stack().limit() - outer.frame_stack().len(),
-			value_stack: outer.value_stack_mut(),
+			value_stack: &mut outer.value_stack,
+			externals: &outer.externals,
 		}
 	}
 }
 
-fn prepare_function_locals(function_type: &FunctionType, function_body: &FuncBody, outer: CallerContext) -> Result<Vec<VariableInstance>, Error> {
+fn prepare_function_locals(function_type: &FunctionType, function_body: &FuncBody, outer: &mut CallerContext) -> Result<Vec<VariableInstance>, Error> {
 	// locals = function arguments + defined locals
 	function_type.params().iter().rev()
 		.map(|param_type| {
@@ -370,7 +416,7 @@ fn get_initializer(expr: &InitExpr, module: &Module, imports: &ModuleImports) ->
 				.ok_or(Error::Global(format!("trying to initialize with external global with index {} in module without import section", index)))
 				.and_then(|s| s.entries().get(index as usize)
 					.ok_or(Error::Global(format!("trying to initialize with external global with index {} in module with {}-entries import section", index, s.entries().len()))))
-				.and_then(|e| imports.global(e))
+				.and_then(|e| imports.global(None, e))
 				.map(|g| g.get())
 		},
 		&Opcode::I32Const(val) => Ok(RuntimeValue::I32(val)),
diff --git a/src/interpreter/program.rs b/src/interpreter/program.rs
index 58bd524..41141f8 100644
--- a/src/interpreter/program.rs
+++ b/src/interpreter/program.rs
@@ -1,10 +1,9 @@
 use std::sync::Arc;
 use std::collections::HashMap;
-use std::collections::hash_map::Entry;
 use parking_lot::RwLock;
 use elements::Module;
 use interpreter::Error;
-use interpreter::env::{self, env_module};
+use interpreter::env::env_module;
 use interpreter::module::{ModuleInstance, ModuleInstanceInterface};
 
 /// Program instance. Program is a set of instantiated modules.
@@ -27,24 +26,12 @@ impl ProgramInstance {
 		})
 	}
 
-	/// Create new program instance with predefined user-defined functions
-	pub fn with_functions(funcs: env::UserFunctions) -> Result<Self, Error> {
-		Ok(ProgramInstance {
-			essence: Arc::new(ProgramInstanceEssence::with_functions(funcs)?),
-		})
-	}
-
 	/// Instantiate module.
 	pub fn add_module(&self, name: &str, module: Module) -> Result<Arc<ModuleInstance>, Error> {
 		let module_instance = Arc::new(ModuleInstance::new(Arc::downgrade(&self.essence), module)?);
-		let mut modules = self.essence.modules.write();
-		match modules.entry(name.into()) {
-			Entry::Occupied(_) => Err(Error::Program(format!("module {} already instantiated", name))),
-			Entry::Vacant(entry) => {
-				entry.insert(module_instance.clone());
-				Ok(module_instance)
-			},
-		}
+		// replace existing module with the same name with new one
+		self.essence.modules.write().insert(name.into(), module_instance.clone());
+		Ok(module_instance)
 	}
 
 	/// Get one of the modules by name
@@ -56,13 +43,8 @@ impl ProgramInstance {
 impl ProgramInstanceEssence {
 	/// Create new program essence.
 	pub fn new() -> Result<Self, Error> {
-		ProgramInstanceEssence::with_functions(HashMap::with_capacity(0))
-	}
-
-	/// Create new program essence with provided user-defined functions
-	pub fn with_functions(funcs: env::UserFunctions) -> Result<Self, Error> {
 		let mut modules = HashMap::new();
-		let env_module: Arc<ModuleInstanceInterface> = Arc::new(env_module(funcs)?);
+		let env_module: Arc<ModuleInstanceInterface> = Arc::new(env_module()?);
 		modules.insert("env".into(), env_module);
 		Ok(ProgramInstanceEssence {
 			modules: RwLock::new(modules),
diff --git a/src/interpreter/runner.rs b/src/interpreter/runner.rs
index 5069895..e25a17b 100644
--- a/src/interpreter/runner.rs
+++ b/src/interpreter/runner.rs
@@ -1,7 +1,9 @@
 use std::mem;
 use std::ops;
 use std::u32;
+use std::sync::Arc;
 use std::fmt::Display;
+use std::collections::HashMap;
 use elements::{Opcode, BlockType, FunctionType};
 use interpreter::Error;
 use interpreter::module::{ModuleInstance, ModuleInstanceInterface, CallerContext, ItemIndex};
@@ -18,17 +20,19 @@ pub struct Interpreter;
 /// Function execution context.
 pub struct FunctionContext<'a> {
 	/// Module instance.
-	module: &'a ModuleInstance,
+	pub module: &'a ModuleInstance,
+	/// Execution-local external modules.
+	pub externals: &'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>,
 	/// Function return type.
-	return_type: BlockType,
+	pub return_type: BlockType,
 	/// Local variables.
-	locals: Vec<VariableInstance>,
+	pub locals: Vec<VariableInstance>,
 	/// Values stack.
-	value_stack: StackWithLimit<RuntimeValue>,
+	pub value_stack: StackWithLimit<RuntimeValue>,
 	/// Blocks frames stack.
-	frame_stack: StackWithLimit<BlockFrame>,
+	pub frame_stack: StackWithLimit<BlockFrame>,
 	/// Current instruction position.
-	position: usize,
+	pub position: usize,
 }
 
 #[derive(Debug, Clone)]
@@ -868,9 +872,10 @@ impl Interpreter {
 }
 
 impl<'a> FunctionContext<'a> {
-	pub fn new(module: &'a ModuleInstance, value_stack_limit: usize, frame_stack_limit: usize, function: &FunctionType, body: &[Opcode], args: Vec<VariableInstance>) -> Result<Self, Error> {
+	pub fn new(module: &'a ModuleInstance, externals: &'a HashMap<String, Arc<ModuleInstanceInterface + 'a>>, value_stack_limit: usize, frame_stack_limit: usize, function: &FunctionType, body: &[Opcode], args: Vec<VariableInstance>) -> Result<Self, Error> {
 		let mut context = FunctionContext {
 			module: module,
+			externals: externals,
 			return_type: function.return_type().map(|vt| BlockType::Value(vt)).unwrap_or(BlockType::NoResult),
 			value_stack: StackWithLimit::with_limit(value_stack_limit),
 			frame_stack: StackWithLimit::with_limit(frame_stack_limit),
@@ -888,6 +893,10 @@ impl<'a> FunctionContext<'a> {
 		self.module
 	}
 
+	pub fn externals(&self) -> &HashMap<String, Arc<ModuleInstanceInterface + 'a>> {
+		&self.externals
+	}
+
 	pub fn call_function(&mut self, index: u32) -> Result<Option<RuntimeValue>, Error> {
 		self.module.call_function(CallerContext::nested(self), ItemIndex::IndexSpace(index))
 	}
diff --git a/src/interpreter/tests/basics.rs b/src/interpreter/tests/basics.rs
index f9d8e9a..fee1201 100644
--- a/src/interpreter/tests/basics.rs
+++ b/src/interpreter/tests/basics.rs
@@ -1,10 +1,13 @@
 ///! Basic tests for instructions/constructions, missing in wabt tests
 
+use std::sync::Arc;
 use builder::module;
 use elements::{ExportEntry, Internal, ImportEntry, External, GlobalEntry, GlobalType,
 	InitExpr, ValueType, Opcodes, Opcode};
 use interpreter::Error;
-use interpreter::module::{ModuleInstanceInterface, CallerContext};
+use interpreter::env_native::{env_native_module, UserFunction, UserFunctions, UserFunctionExecutor};
+use interpreter::memory::MemoryInstance;
+use interpreter::module::{ModuleInstanceInterface, CallerContext, ItemIndex, ExecutionParams};
 use interpreter::program::ProgramInstance;
 use interpreter::value::RuntimeValue;
 
@@ -38,8 +41,8 @@ fn import_function() {
 	let external_module = program.add_module("external_module", module1).unwrap();
 	let main_module = program.add_module("main", module2).unwrap();
 
-	assert_eq!(external_module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(3));
-	assert_eq!(main_module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(10));
+	assert_eq!(external_module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(3));
+	assert_eq!(main_module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(10));
 }
 
 #[test]
@@ -72,7 +75,7 @@ fn wrong_import() {
 	let _side_module_instance = program.add_module("side_module", side_module).unwrap();
 	let module_instance = program.add_module("main", module).unwrap();
 
-	assert!(module_instance.execute_index(1, vec![]).is_err());	
+	assert!(module_instance.execute_index(1, vec![].into()).is_err());	
 }
 
 #[test]
@@ -115,112 +118,102 @@ fn global_get_set() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(50));
-	assert_eq!(module.execute_index(1, vec![]).unwrap_err(), Error::Variable("trying to update immutable variable".into()));
-	assert_eq!(module.execute_index(2, vec![]).unwrap_err(), Error::Variable("trying to update variable of type I32 with value of type Some(I64)".into()));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(50));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap_err(), Error::Variable("trying to update immutable variable".into()));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap_err(), Error::Variable("trying to update variable of type I32 with value of type Some(I64)".into()));
 }
 
 #[test]
-fn with_user_functions() {
-	use interpreter::{UserFunction, UserFunctions, ModuleInstance};
+fn single_program_different_modules() {
+	// user function executor
+	struct FunctionExecutor {
+		pub memory: Arc<MemoryInstance>,
+		pub values: Vec<i32>,
+	}
+
+	impl UserFunctionExecutor for FunctionExecutor {
+		fn execute(&mut self, name: &str, context: CallerContext) -> Result<Option<RuntimeValue>, Error> {
+			match name {
+				"add" => {
+					let memory_value = self.memory.get(0, 1).unwrap()[0];
+					let fn_argument = context.value_stack.pop_as::<u32>().unwrap() as u8;
+					let sum = memory_value + fn_argument;
+					self.memory.set(0, &vec![sum]).unwrap();
+					self.values.push(sum as i32);
+					Ok(Some(RuntimeValue::I32(sum as i32)))
+				},
+				"sub" => {
+					let memory_value = self.memory.get(0, 1).unwrap()[0];
+					let fn_argument = context.value_stack.pop_as::<u32>().unwrap() as u8;
+					let diff = memory_value - fn_argument;
+					self.memory.set(0, &vec![diff]).unwrap();
+					self.values.push(diff as i32);
+					Ok(Some(RuntimeValue::I32(diff as i32)))
+				},
+				_ => Err(Error::Trap("not implemented".into())),
+			}
+		}
+	}
+
+	// create new program
+	let program = ProgramInstance::new().unwrap();
+	// => env module is created
+	let env_instance = program.module("env").unwrap();
+	// => linear memory is created
+	let env_memory = env_instance.memory(ItemIndex::Internal(0)).unwrap();
 
 	let module = module()
-		.with_import(ImportEntry::new("env".into(), "custom_alloc".into(), External::Function(0)))
-		.with_import(ImportEntry::new("env".into(), "custom_increment".into(), External::Function(0)))
+		.with_import(ImportEntry::new("env".into(), "add".into(), External::Function(0)))
+		.with_import(ImportEntry::new("env".into(), "sub".into(), External::Function(0)))
 		.function()
-			.signature().return_type().i32().build()
+			.signature().param().i32().return_type().i32().build()
 			.body().with_opcodes(Opcodes::new(vec![
-				Opcode::I32Const(32),
+				Opcode::GetLocal(0),
 				Opcode::Call(0),
 				Opcode::End,
 			])).build()
 			.build()
+		.function()
+			.signature().param().i32().return_type().i32().build()
+			.body().with_opcodes(Opcodes::new(vec![
+				Opcode::GetLocal(0),
+				Opcode::Call(1),
+				Opcode::End,
+			])).build()
+			.build()
 		.build();
 
-	let mut top = 0i32;
-	let mut user_functions = UserFunctions::new();
-	user_functions.insert(
-		"custom_alloc".to_owned(), 
-		UserFunction {
-			params: vec![ValueType::I32],
-			result: Some(ValueType::I32),
-			closure: Box::new(move |_module: &ModuleInstance, context: CallerContext| {
-				let prev = top;
-				top = top + context.value_stack.pop_as::<i32>()?;
-				Ok(Some(prev.into()))
-			}),
-		}
-	);
+	// load module
+	let module_instance = program.add_module("main", module).unwrap();
 
-	let mut rolling = 9999i32;
-	user_functions.insert(
-		"custom_increment".to_owned(), 
-		UserFunction {
-			params: vec![ValueType::I32],
-			result: Some(ValueType::I32),
-			closure: Box::new(move |_module: &ModuleInstance, _context: CallerContext|  {
-				rolling = rolling + 1;
-				Ok(Some(rolling.into()))
-			}),
-		}
-	);	
+	let mut executor = FunctionExecutor {
+		memory: env_memory.clone(),
+		values: Vec::new(),
+	};
+	{
+		// create native env module with native add && sub implementations
+		let functions: UserFunctions = UserFunctions {
+			executor: &mut executor,
+			functions: vec![UserFunction {
+				name: "add".into(),
+				params: vec![ValueType::I32],
+				result: Some(ValueType::I32),
+			}, UserFunction {
+				name: "sub".into(),
+				params: vec![ValueType::I32],
+				result: Some(ValueType::I32),
+			}],
+		};
+		let native_env_instance = Arc::new(env_native_module(env_instance, functions).unwrap());
 
-	let program = ProgramInstance::with_functions(user_functions).unwrap();
-	let module_instance = program.add_module("main", module).unwrap();	
+		// execute functions
+		let params = ExecutionParams::with_external("env".into(), native_env_instance);
 
-	// internal function using first import
-	assert_eq!(module_instance.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));	
-	assert_eq!(module_instance.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(32));	
-	assert_eq!(module_instance.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(64));	
-	
-	// second import
-	assert_eq!(module_instance.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(10000));	
-	assert_eq!(module_instance.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(10001));	
+		assert_eq!(module_instance.execute_index(2, params.clone().add_argument(RuntimeValue::I32(7))).unwrap().unwrap(), RuntimeValue::I32(7));
+		assert_eq!(module_instance.execute_index(2, params.clone().add_argument(RuntimeValue::I32(50))).unwrap().unwrap(), RuntimeValue::I32(57));
+		assert_eq!(module_instance.execute_index(3, params.clone().add_argument(RuntimeValue::I32(15))).unwrap().unwrap(), RuntimeValue::I32(42));
+	}
+
+	assert_eq!(executor.memory.get(0, 1).unwrap()[0], 42);
+	assert_eq!(executor.values, vec![7, 57, 42]);
 }
-
-#[test]
-fn with_user_functions_extended() {
-	use interpreter::{UserFunction, UserFunctions, UserFunctionInterface, ModuleInstance};
-
-	struct UserMAlloc {
-		top: i32,
-	}
-
-	impl UserFunctionInterface for UserMAlloc {
-		fn call(&mut self, _module: &ModuleInstance, context: CallerContext) -> Result<Option<RuntimeValue>, Error> {
-			let prev = self.top;
-			self.top += context.value_stack.pop_as::<i32>()?;
-			Ok(Some(prev.into()))
-		}
-	}
-
-	let module = module()
-		.with_import(ImportEntry::new("env".into(), "_malloc".into(), External::Function(0)))
-		.function()
-			.signature().return_type().i32().build()
-			.body().with_opcodes(Opcodes::new(vec![
-				Opcode::I32Const(32),
-				Opcode::Call(0),
-				Opcode::End,
-			])).build()
-			.build()
-		.build();
-
-	let mut user_functions = UserFunctions::new();
-	user_functions.insert(
-		"_malloc".to_owned(), 
-		UserFunction {
-			params: vec![ValueType::I32],
-			result: Some(ValueType::I32),
-			closure: Box::new(UserMAlloc { top: 0 }),
-		}
-	);
-
-	let program = ProgramInstance::with_functions(user_functions).unwrap();
-	let module_instance = program.add_module("main", module).unwrap();	
-
-	// internal function using first import
-	assert_eq!(module_instance.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));	
-	assert_eq!(module_instance.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(32));	
-	assert_eq!(module_instance.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(64));	
-}
\ No newline at end of file
diff --git a/src/interpreter/tests/wabt.rs b/src/interpreter/tests/wabt.rs
index d069392..a0bfda2 100644
--- a/src/interpreter/tests/wabt.rs
+++ b/src/interpreter/tests/wabt.rs
@@ -1,6 +1,7 @@
 ///! Tests from https://github.com/WebAssembly/wabt/tree/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp
 
 use std::sync::Weak;
+use std::collections::HashMap;
 use builder::module;
 use elements::{Module, ValueType, Opcodes, Opcode, BlockType, FunctionType};
 use interpreter::Error;
@@ -13,7 +14,8 @@ use interpreter::variable::{VariableInstance, VariableType};
 fn run_function_i32(body: &Opcodes, arg: i32) -> Result<i32, Error> {
 	let ftype = FunctionType::new(vec![ValueType::I32], Some(ValueType::I32));
 	let module = ModuleInstance::new(Weak::default(), Module::default()).unwrap();
-	let mut context = FunctionContext::new(&module, 1024, 1024, &ftype, body.elements(), vec![
+	let externals = HashMap::new();
+	let mut context = FunctionContext::new(&module, &externals, 1024, 1024, &ftype, body.elements(), vec![
 			VariableInstance::new(true, VariableType::I32, RuntimeValue::I32(arg)).unwrap(),	// arg
 			VariableInstance::new(true, VariableType::I32, RuntimeValue::I32(0)).unwrap(),		// local1
 			VariableInstance::new(true, VariableType::I32, RuntimeValue::I32(0)).unwrap(),		// local2
@@ -522,11 +524,11 @@ fn return_void() {
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
 
-	module.execute_main(vec![RuntimeValue::I32(0)]).unwrap();
+	module.execute_main(vec![RuntimeValue::I32(0)].into()).unwrap();
 	let memory = module.memory(ItemIndex::IndexSpace(0)).unwrap();
 	assert_eq!(memory.get(0, 4).unwrap(), vec![0, 0, 0, 0]);
 
-	module.execute_main(vec![RuntimeValue::I32(1)]).unwrap();
+	module.execute_main(vec![RuntimeValue::I32(1)].into()).unwrap();
 	let memory = module.memory(ItemIndex::IndexSpace(0)).unwrap();
 	assert_eq!(memory.get(0, 4).unwrap(), vec![1, 0, 0, 0]);
 }
@@ -580,7 +582,7 @@ fn call_1() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_main(vec![]).unwrap().unwrap(), RuntimeValue::I32(10));
+	assert_eq!(module.execute_main(vec![].into()).unwrap().unwrap(), RuntimeValue::I32(10));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/call.txt#L23
@@ -629,7 +631,7 @@ fn call_2() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_main(vec![]).unwrap().unwrap(), RuntimeValue::I32(3628800));
+	assert_eq!(module.execute_main(vec![].into()).unwrap().unwrap(), RuntimeValue::I32(3628800));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/call-zero-args.txt
@@ -674,7 +676,7 @@ fn call_zero_args() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_main(vec![]).unwrap().unwrap(), RuntimeValue::I32(43));
+	assert_eq!(module.execute_main(vec![].into()).unwrap().unwrap(), RuntimeValue::I32(43));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/callindirect.txt#L31
@@ -720,8 +722,8 @@ fn callindirect_1() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/callindirect.txt#L39
@@ -793,11 +795,11 @@ fn callindirect_2() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::I32(14));
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::I32(6));
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(2)]).unwrap_err(),
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::I32(14));
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::I32(6));
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(2)].into()).unwrap_err(),
 		Error::Function("expected function with signature ([I32, I32]) -> Some(I32) when got with ([I32]) -> Some(I32)".into()));
-	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(3)]).unwrap_err(),
+	assert_eq!(module.execute_main(vec![RuntimeValue::I32(10), RuntimeValue::I32(4), RuntimeValue::I32(3)].into()).unwrap_err(),
 		Error::Table("trying to read table item with index 3 when there are only 3 items".into()));
 }
 
@@ -861,14 +863,14 @@ fn select() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::I32(2));
-	assert_eq!(module.execute_index(0, vec![RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(1, vec![RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::I64(2));
-	assert_eq!(module.execute_index(1, vec![RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::I64(1));
-	assert_eq!(module.execute_index(2, vec![RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::F32(2f32));
-	assert_eq!(module.execute_index(2, vec![RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::F32(1f32));
-	assert_eq!(module.execute_index(3, vec![RuntimeValue::I32(0)]).unwrap().unwrap(), RuntimeValue::F64(2f64));
-	assert_eq!(module.execute_index(3, vec![RuntimeValue::I32(1)]).unwrap().unwrap(), RuntimeValue::F64(1f64));
+	assert_eq!(module.execute_index(0, vec![RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::I32(2));
+	assert_eq!(module.execute_index(0, vec![RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(1, vec![RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::I64(2));
+	assert_eq!(module.execute_index(1, vec![RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::I64(1));
+	assert_eq!(module.execute_index(2, vec![RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::F32(2f32));
+	assert_eq!(module.execute_index(2, vec![RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::F32(1f32));
+	assert_eq!(module.execute_index(3, vec![RuntimeValue::I32(0)].into()).unwrap().unwrap(), RuntimeValue::F64(2f64));
+	assert_eq!(module.execute_index(3, vec![RuntimeValue::I32(1)].into()).unwrap().unwrap(), RuntimeValue::F64(1f64));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/binary.txt#L3
@@ -1014,21 +1016,21 @@ fn binary_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(3));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(16));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(21));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(-2)); // 4294967294
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(2147483646));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1)); // 4294967295
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I32(15));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I32(14));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I32(-800)); // 4294966496
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I32(536870899));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I32(-13)); // 4294967283
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I32(-793)); // 4294966503
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1610612749)); // 2684354547
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(3));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(16));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(21));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-2)); // 4294967294
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(2147483646));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1)); // 4294967295
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(15));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(14));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-800)); // 4294966496
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(536870899));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-13)); // 4294967283
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-793)); // 4294966503
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1610612749)); // 2684354547
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/binary.txt#L65
@@ -1174,21 +1176,21 @@ fn binary_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I64(3));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I64(16));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I64(21));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I64(-2)); // 18446744073709551614
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I64(9223372036854775806));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1)); // 18446744073709551615
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I64(1));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I64(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I64(15));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I64(14));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I64(-800)); // 18446744073709550816
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I64(2305843009213693939));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I64(-13)); // 18446744073709551603
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I64(-793)); // 18446744073709550823
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I64(-6917529027641081869)); // 11529215046068469747
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(3));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(16));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(21));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-2)); // 18446744073709551614
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(9223372036854775806));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1)); // 18446744073709551615
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(1));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(15));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(14));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-800)); // 18446744073709550816
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(2305843009213693939));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-13)); // 18446744073709551603
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-793)); // 18446744073709550823
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-6917529027641081869)); // 11529215046068469747
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/binary.txt#L3
@@ -1264,13 +1266,13 @@ fn binary_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F32(5.000000));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F32(-9995.500000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F32(-8487.187500));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::F32(-500000000.000000));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F32(0.000000));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::F32(0.000000));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::F32(0.000000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(5.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-9995.500000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-8487.187500));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-500000000.000000));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(0.000000));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(0.000000));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(0.000000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/binary.txt#L157
@@ -1346,15 +1348,15 @@ fn binary_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F64(1111111110.000000));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F64(123400000000000007812762268812638756607430593436581896388608.000000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F64(-15179717820000.000000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(1111111110.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(123400000000000007812762268812638756607430593436581896388608.000000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-15179717820000.000000));
 	// in wabt result is 99999999999999998083559617243737459057312001403031879309116481015410011220367858297629826861622
 	// but the actual (and correct) result is 1e150
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::F64(1e150));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F64(0.000000));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::F64(0.000000));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::F64(0.000000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(1e150));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(0.000000));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(0.000000));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(0.000000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/cast.txt
@@ -1399,10 +1401,10 @@ fn cast() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F32(4.5));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1067450368)); // 3227516928
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F64(125.125000));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I64(4758506566875873280));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(4.5));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1067450368)); // 3227516928
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(125.125000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(4758506566875873280));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/compare.txt#L3
@@ -1665,34 +1667,34 @@ fn compare_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(15, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(16, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(17, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(18, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(19, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(20, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(21, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(22, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(23, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(24, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(25, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(26, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(27, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(15, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(16, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(17, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(18, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(19, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(20, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(21, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(22, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(23, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(24, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(25, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(26, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(27, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/compare.txt#L123
@@ -1955,34 +1957,34 @@ fn compare_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(15, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(16, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(17, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(18, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(19, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(20, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(21, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(22, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(23, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(24, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(25, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(26, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(27, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(15, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(16, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(17, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(18, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(19, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(20, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(21, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(22, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(23, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(24, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(25, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(26, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(27, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/compare.txt#L246
@@ -2139,22 +2141,22 @@ fn compare_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(15, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(15, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/compare.txt#L317
@@ -2311,22 +2313,22 @@ fn compare_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(10, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(11, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(12, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(13, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(14, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(15, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(10, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(11, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(12, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(13, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(14, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(15, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/convert.txt#L3
@@ -2379,11 +2381,11 @@ fn convert_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1));				// 4294967295
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(-100));			// 4294967196
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1294967296));	// 3000000000
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(-100));			// 4294967196
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1294967296));	// 3000000000
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1));				// 4294967295
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-100));			// 4294967196
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1294967296));	// 3000000000
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-100));			// 4294967196
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1294967296));	// 3000000000
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/convert.txt#L21
@@ -2452,12 +2454,12 @@ fn convert_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I64(4294967295));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1)); // 18446744073709551615
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(4294967295));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1)); // 18446744073709551615
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/convert.txt#L50
@@ -2510,11 +2512,11 @@ fn convert_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F32(-1.000000));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F32(4294967296.000000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F32(12345679.000000));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::F32(0.000000));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F32(0.000000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-1.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(4294967296.000000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(12345679.000000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(0.000000));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(0.000000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/convert.txt#L50
@@ -2567,11 +2569,11 @@ fn convert_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F64(-1.000000));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F64(4294967295.000000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F64(12345679.000000));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::F64(0.000000));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F64(0.000000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-1.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(4294967295.000000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(12345679.000000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(0.000000));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(0.000000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/load.txt#L9
@@ -2627,11 +2629,11 @@ fn load_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(255));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(65535));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(255));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(65535));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/load.txt#L26
@@ -2703,13 +2705,13 @@ fn load_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I64(-1));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I64(255));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::I64(65535));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::I64(4294967295));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-1));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(255));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(65535));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(4294967295));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/load.txt#L50
@@ -2733,7 +2735,7 @@ fn load_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F32(25.750000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(25.750000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/load.txt#L54
@@ -2757,7 +2759,7 @@ fn load_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::F64(1023.875000));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(1023.875000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/store.txt#L5
@@ -2814,9 +2816,9 @@ fn store_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(-16909061));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(-859059511));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(-123456));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-16909061));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-859059511));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-123456));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/store.txt#L38
@@ -2884,10 +2886,10 @@ fn store_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I64(4278058235));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I64(3435907785));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I64(4294843840));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I64(-4981613551475109875));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(4278058235));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(3435907785));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(4294843840));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(-4981613551475109875));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/store.txt#L78
@@ -2912,7 +2914,7 @@ fn store_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(1069547520));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1069547520));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/store.txt#L85
@@ -2937,7 +2939,7 @@ fn store_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(-1064352256));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(-1064352256));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/unary.txt#L12
@@ -2988,11 +2990,11 @@ fn unary_i32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I32(24));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(7));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(24));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(7));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/unary.txt#L29
@@ -3043,11 +3045,11 @@ fn unary_i64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(0, vec![]).unwrap().unwrap(), RuntimeValue::I32(0));
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::I64(56));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I64(7));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::I64(1));
+	assert_eq!(module.execute_index(0, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(0));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(56));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(7));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::I64(1));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/unary.txt#L46
@@ -3142,15 +3144,15 @@ fn unary_f32() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F32(-100.000000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F32(100.000000));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F32(10.000000));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::F32(-0.000000));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::F32(-1.000000));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::F32(-0.000000));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::F32(1.000000));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::F32(2.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-100.000000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(100.000000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(10.000000));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-0.000000));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-1.000000));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(-0.000000));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(1.000000));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::F32(2.000000));
 }
 
 /// https://github.com/WebAssembly/wabt/blob/8e1f6031e9889ba770c7be4a9b084da5f14456a0/test/interp/unary.txt#L76
@@ -3245,13 +3247,13 @@ fn unary_f64() {
 
 	let program = ProgramInstance::new().unwrap();
 	let module = program.add_module("main", module).unwrap();
-	assert_eq!(module.execute_index(1, vec![]).unwrap().unwrap(), RuntimeValue::F64(-100.000000));
-	assert_eq!(module.execute_index(2, vec![]).unwrap().unwrap(), RuntimeValue::F64(100.000000));
-	assert_eq!(module.execute_index(3, vec![]).unwrap().unwrap(), RuntimeValue::I32(1));
-	assert_eq!(module.execute_index(4, vec![]).unwrap().unwrap(), RuntimeValue::F64(10.000000));
-	assert_eq!(module.execute_index(5, vec![]).unwrap().unwrap(), RuntimeValue::F64(-0.000000));
-	assert_eq!(module.execute_index(6, vec![]).unwrap().unwrap(), RuntimeValue::F64(-1.000000));
-	assert_eq!(module.execute_index(7, vec![]).unwrap().unwrap(), RuntimeValue::F64(-0.000000));
-	assert_eq!(module.execute_index(8, vec![]).unwrap().unwrap(), RuntimeValue::F64(1.000000));
-	assert_eq!(module.execute_index(9, vec![]).unwrap().unwrap(), RuntimeValue::F64(2.000000));
+	assert_eq!(module.execute_index(1, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-100.000000));
+	assert_eq!(module.execute_index(2, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(100.000000));
+	assert_eq!(module.execute_index(3, vec![].into()).unwrap().unwrap(), RuntimeValue::I32(1));
+	assert_eq!(module.execute_index(4, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(10.000000));
+	assert_eq!(module.execute_index(5, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-0.000000));
+	assert_eq!(module.execute_index(6, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-1.000000));
+	assert_eq!(module.execute_index(7, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(-0.000000));
+	assert_eq!(module.execute_index(8, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(1.000000));
+	assert_eq!(module.execute_index(9, vec![].into()).unwrap().unwrap(), RuntimeValue::F64(2.000000));
 }