Introduce tests which demonstrate bad wasm compiler.

substrate/wasm-runtime/polkadot/src/lib.rs

@@ -38,12 +38,6 @@ use runtime_support::prelude::*;
 use slicable::Slicable;
 use primitives::{Block, UncheckedTransaction};
 
-/// A simple test.
-pub fn simple_test(input: &[u8]) -> Vec<u8> {
-	println!("Executing block");
-	Vec::new()
-}
-
 /// Execute a block, with `input` being the canonical serialisation of the block. Returns the
 /// empty vector.
 pub fn execute_block(input: &[u8]) -> Vec<u8> {
@@ -53,11 +47,12 @@ pub fn execute_block(input: &[u8]) -> Vec<u8> {
 
 /// Execute a given, serialised, transaction. Returns the empty vector.
 pub fn execute_transaction(input: &[u8]) -> Vec<u8> {
-	println!("Deserialising... {:?}", input);
+	if input.len() == 0 {
+		panic!("no transaction data given!");
+	}
 	let utx = UncheckedTransaction::from_slice(input).unwrap();
-	println!("Forwarding... {:?}", utx);
 	runtime::system::execute_transaction(&utx);
-	Vec::new()
+	input.to_vec()//Vec::new()
 }
 
 impl_stubs!(execute_block, execute_transaction);

substrate/wasm-runtime/polkadot/src/runtime/system.rs

@@ -84,7 +84,6 @@ pub fn execute_block(mut block: Block) {
 
 /// Execute a given transaction.
 pub fn execute_transaction(utx: &UncheckedTransaction) {
-	println!("Executing...");
 	// Verify the signature is good.
 	assert!(utx.ed25519_verify(), "All transactions should be properly signed");
 
@@ -98,8 +97,6 @@ pub fn execute_transaction(utx: &UncheckedTransaction) {
 	// increment nonce in storage
 	(expected_nonce + 1).store(&nonce_key);
 
-	println!("Dispatching...");
-
 	// decode parameters and dispatch
 	tx.function.dispatch(&tx.signed, &tx.input_data);
 }

substrate/wasm-runtime/support/src/lib.rs

@@ -144,7 +144,13 @@ macro_rules! impl_stubs {
 					};
 
 					let output = super::$name(&input[..]);
-					&output[0] as *const u8 as u64 + ((output.len() as u64) << 32)
+					// things break if we try to take the address of an unallocated vec, so we
+					// shortcircuit the empty output case.
+					if output.len() > 0 {
+						&output[0] as *const u8 as u64 + ((output.len() as u64) << 32)
+					} else {
+						0
+					}
 				}
 			)*
 		}

substrate/wasm-runtime/test/src/lib.rs

@@ -43,4 +43,22 @@ fn test_data_in(input: &[u8]) -> Vec<u8> {
 	b"all ok!".to_vec()
 }
 
-impl_stubs!(test_data_in, test_blake2_256, test_twox_256, test_twox_128, test_ed25519_verify);
+fn test_empty_return(_input: &[u8]) -> Vec<u8> {
+	Vec::new()
+}
+
+fn test_panic(_input: &[u8]) -> Vec<u8> {
+	panic!("test panic");
+}
+
+fn test_conditional_panic(input: &[u8]) -> Vec<u8> {
+	if input.len() > 0 {
+		panic!("test panic");
+	} else {
+		assert!(input.len() > 0);
+	}
+	input.to_vec()
+}
+
+impl_stubs!(test_data_in, test_empty_return, test_panic, test_conditional_panic,
+	test_blake2_256, test_twox_256, test_twox_128, test_ed25519_verify);