Use a sensible default value for block.gaslimit (#596)

* added a sensible value for block.gaslimit

* added test

examples/solidity/basic/gaslimit.sol

@@ -0,0 +1,7 @@
+contract C { 
+
+  function echidna_gaslimit() public returns (bool) {
+    return block.gaslimit > 0;
+  }
+
+}

lib/Echidna/RPC.hs

@@ -138,5 +138,5 @@ execEthenoTxs ts addr et = do
 -- | For an etheno txn, set up VM to execute txn
 setupEthenoTx :: (MonadState x m, Has VM x) => Etheno -> m ()
 setupEthenoTx (AccountCreated _) = pure ()
-setupEthenoTx (ContractCreated f c _ _ d v) = setupTx $ createTxWithValue d f c unlimitedGasPerBlock (w256 v)
-setupEthenoTx (FunctionCall f t _ _ d v) = setupTx $ Tx (SolCalldata d) f t unlimitedGasPerBlock 0 (w256 v) (0, 0)
+setupEthenoTx (ContractCreated f c _ _ d v) = setupTx $ createTxWithValue d f c (fromInteger unlimitedGasPerBlock) (w256 v)
+setupEthenoTx (FunctionCall f t _ _ d v) = setupTx $ Tx (SolCalldata d) f t (fromInteger unlimitedGasPerBlock) 0 (w256 v) (0, 0)

lib/Echidna/Solidity.hs

@@ -157,7 +157,7 @@ loadLibraries :: (MonadIO m, MonadThrow m, MonadReader x m, Has SolConf x)
               => [SolcContract] -> Addr -> Addr -> VM -> m VM
 loadLibraries []     _  _ vm = return vm
 loadLibraries (l:ls) la d vm = loadLibraries ls (la + 1) d =<< loadRest
-  where loadRest = execStateT (execTx $ createTx (l ^. creationCode) d la unlimitedGasPerBlock) vm
+  where loadRest = execStateT (execTx $ createTx (l ^. creationCode) d la (fromInteger unlimitedGasPerBlock)) vm
 
 -- | Generate a string to use as argument in solc to link libraries starting from addrLibrary
 linkLibraries :: [String] -> String
@@ -214,7 +214,7 @@ loadSpecified name cs = do
 
   -- Set up initial VM, either with chosen contract or Etheno initialization file
   -- need to use snd to add to ABI dict
-  blank' <- maybe (pure (initialVM & block . maxCodeSize .~ w256 (fromInteger mcs)))
+  blank' <- maybe (pure (initialVM & block . gaslimit .~ fromInteger unlimitedGasPerBlock & block . maxCodeSize .~ w256 (fromInteger mcs)))
                   (loadEthenoBatch $ fst <$> tests)
                   fp
   let blank = populateAddresses (NE.toList ads |> d) bala blank'
@@ -231,7 +231,7 @@ loadSpecified name cs = do
     Just (t,_) -> throwM $ TestArgsFound t                      -- Test args check
     Nothing    -> do
       vm <- loadLibraries ls addrLibrary d blank
-      let transaction = unless (isJust fp) $ void . execTx $ createTxWithValue bc d ca unlimitedGasPerBlock (w256 $ fromInteger balc)
+      let transaction = unless (isJust fp) $ void . execTx $ createTxWithValue bc d ca (fromInteger unlimitedGasPerBlock) (w256 $ fromInteger balc)
       vm' <- execStateT transaction vm
       case currentContract vm' of
         Just _  -> return (vm', c ^. eventMap, neFuns, fst <$> tests, abiMapping)

lib/Echidna/Types/Tx.hs

@@ -29,7 +29,7 @@ $(deriveJSON defaultOptions ''TxCall)
 maxGasPerBlock :: Integer
 maxGasPerBlock = 12500000 -- https://cointelegraph.com/news/ethereum-miners-vote-to-increase-gas-limit-causing-community-debate
 
-unlimitedGasPerBlock :: Word
+unlimitedGasPerBlock :: Integer
 unlimitedGasPerBlock = 0xffffffff
 
 defaultTimeDelay :: Integer

src/test/Tests/Integration.hs

@@ -142,6 +142,8 @@ integrationTests = testGroup "Solidity Integration Testing"
       , ("f_open1 gas estimate wrong",             gasInRange "f_open1"  18000 23000)
       , ("push_b gas estimate wrong",              gasInRange "push_b"   39000 45000)
       ]
+  , testContract "basic/gaslimit.sol"  Nothing
+      [ ("echidna_gaslimit passed",                passed      "echidna_gaslimit") ] 
   ,  testContract "coverage/boolean.sol"       (Just "coverage/boolean.yaml")
       [ ("echidna_true failed",                    passed     "echidna_true")
       , ("unexpected corpus count ",               countCorpus 5)]