Wasm executor should provide stubs for unknown externs (wasmi)

client/executor/runtime-test/src/lib.rs

@@ -18,7 +18,23 @@ use sp_runtime::{print, traits::{BlakeTwo256, Hash}};
 #[cfg(not(feature = "std"))]
 use sp_core::{ed25519, sr25519};
 
+extern "C" {
+	#[allow(dead_code)]
+	fn missing_external();
+
+	#[allow(dead_code)]
+	fn yet_another_missing_external();
+}
+
 sp_core::wasm_export_functions! {
+	fn test_calling_missing_external() {
+		unsafe { missing_external() }
+	}
+
+	fn test_calling_yet_another_missing_external() {
+		unsafe { yet_another_missing_external() }
+	}
+
 	fn test_data_in(input: Vec<u8>) -> Vec<u8> {
 		print("set_storage");
 		storage::set(b"input", &input);

client/executor/src/integration_tests/mod.rs

@@ -32,6 +32,49 @@ use crate::WasmExecutionMethod;
 
 pub type TestExternalities = CoreTestExternalities<Blake2Hasher, u64>;
 
+#[cfg(feature = "wasmtime")]
+mod wasmtime_missing_externals {
+	use sp_wasm_interface::{Function, FunctionContext, HostFunctions, Result, Signature, Value};
+
+	pub struct WasmtimeHostFunctions;
+
+	impl HostFunctions for WasmtimeHostFunctions {
+		fn host_functions() -> Vec<&'static dyn Function> {
+			vec![MISSING_EXTERNAL_FUNCTION, YET_ANOTHER_MISSING_EXTERNAL_FUNCTION]
+		}
+	}
+
+	struct MissingExternalFunction(&'static str);
+
+	impl Function for MissingExternalFunction {
+		fn name(&self) -> &str { self.0 }
+
+		fn signature(&self) -> Signature {
+			Signature::new(vec![], None)
+		}
+
+		fn execute(
+			&self,
+			_context: &mut dyn FunctionContext,
+			_args: &mut dyn Iterator<Item = Value>,
+		) -> Result<Option<Value>> {
+			panic!("should not be called");
+		}
+	}
+
+	static MISSING_EXTERNAL_FUNCTION: &'static MissingExternalFunction =
+		&MissingExternalFunction("missing_external");
+	static YET_ANOTHER_MISSING_EXTERNAL_FUNCTION: &'static MissingExternalFunction =
+		&MissingExternalFunction("yet_another_missing_external");
+}
+
+#[cfg(feature = "wasmtime")]
+type HostFunctions =
+	(wasmtime_missing_externals::WasmtimeHostFunctions, sp_io::SubstrateHostFunctions);
+
+#[cfg(not(feature = "wasmtime"))]
+type HostFunctions = sp_io::SubstrateHostFunctions;
+
 fn call_in_wasm<E: Externalities>(
 	function: &str,
 	call_data: &[u8],
@@ -40,13 +83,14 @@ fn call_in_wasm<E: Externalities>(
 	code: &[u8],
 	heap_pages: u64,
 ) -> crate::error::Result<Vec<u8>> {
-	crate::call_in_wasm::<E, sp_io::SubstrateHostFunctions>(
+	crate::call_in_wasm::<E, HostFunctions>(
 		function,
 		call_data,
 		execution_method,
 		ext,
 		code,
 		heap_pages,
+		true,
 	)
 }
 
@@ -68,6 +112,44 @@ fn returning_should_work(wasm_method: WasmExecutionMethod) {
 	assert_eq!(output, vec![0u8; 0]);
 }
 
+#[test_case(WasmExecutionMethod::Interpreted)]
+#[cfg_attr(feature = "wasmtime", test_case(WasmExecutionMethod::Compiled))]
+#[should_panic(expected = "function missing_external does not exist")]
+#[cfg(not(feature = "wasmtime"))]
+fn call_not_existing_function(wasm_method: WasmExecutionMethod) {
+	let mut ext = TestExternalities::default();
+	let mut ext = ext.ext();
+	let test_code = WASM_BINARY;
+
+	call_in_wasm(
+		"test_calling_missing_external",
+		&[],
+		wasm_method,
+		&mut ext,
+		&test_code[..],
+		8,
+	).unwrap();
+}
+
+#[test_case(WasmExecutionMethod::Interpreted)]
+#[cfg_attr(feature = "wasmtime", test_case(WasmExecutionMethod::Compiled))]
+#[should_panic(expected = "function yet_another_missing_external does not exist")]
+#[cfg(not(feature = "wasmtime"))]
+fn call_yet_another_not_existing_function(wasm_method: WasmExecutionMethod) {
+	let mut ext = TestExternalities::default();
+	let mut ext = ext.ext();
+	let test_code = WASM_BINARY;
+
+	call_in_wasm(
+		"test_calling_yet_another_missing_external",
+		&[],
+		wasm_method,
+		&mut ext,
+		&test_code[..],
+		8,
+	).unwrap();
+}
+
 #[test_case(WasmExecutionMethod::Interpreted)]
 #[cfg_attr(feature = "wasmtime", test_case(WasmExecutionMethod::Compiled))]
 fn panicking_should_work(wasm_method: WasmExecutionMethod) {

client/executor/src/lib.rs

@@ -67,12 +67,14 @@ pub fn call_in_wasm<E: Externalities, HF: sp_wasm_interface::HostFunctions>(
 	ext: &mut E,
 	code: &[u8],
 	heap_pages: u64,
+	allow_missing_imports: bool,
 ) -> error::Result<Vec<u8>> {
 	let mut instance = wasm_runtime::create_wasm_runtime_with_code(
 		execution_method,
 		heap_pages,
 		code,
 		HF::host_functions(),
+		allow_missing_imports,
 	)?;
 	instance.call(ext, function, call_data)
 }
@@ -103,6 +105,7 @@ mod tests {
 			&mut ext,
 			&WASM_BINARY,
 			8,
+			true,
 		).unwrap();
 		assert_eq!(res, vec![0u8; 0]);
 	}

client/executor/src/wasm_runtime.rs

@@ -191,10 +191,11 @@ pub fn create_wasm_runtime_with_code(
 	heap_pages: u64,
 	code: &[u8],
 	host_functions: Vec<&'static dyn Function>,
+	allow_missing_imports: bool,
 ) -> Result<Box<dyn WasmRuntime>, WasmError> {
 	match wasm_method {
 		WasmExecutionMethod::Interpreted =>
-			sc_executor_wasmi::create_instance(code, heap_pages, host_functions)
+			sc_executor_wasmi::create_instance(code, heap_pages, host_functions, allow_missing_imports)
 				.map(|runtime| -> Box<dyn WasmRuntime> { Box::new(runtime) }),
 		#[cfg(feature = "wasmtime")]
 		WasmExecutionMethod::Compiled =>
@@ -212,7 +213,7 @@ fn create_versioned_wasm_runtime<E: Externalities>(
 	let code = ext
 		.original_storage(well_known_keys::CODE)
 		.ok_or(WasmError::CodeNotFound)?;
-	let mut runtime = create_wasm_runtime_with_code(wasm_method, heap_pages, &code, host_functions)?;
+	let mut runtime = create_wasm_runtime_with_code(wasm_method, heap_pages, &code, host_functions, false)?;
 
 	// Call to determine runtime version.
 	let version_result = {