Merge pull request #1661 from ethereum/asm-revert

Implement REVERT (EIP140)

Changelog.md

@@ -2,6 +2,8 @@
 
 Features:
  * Add ``assert(condition)``, which throws if condition is false.
+ * Code generator: Support ``revert()`` to abort with rolling back, but not consuming all gas.
+ * Inline assembly: Support ``revert`` (EIP140) as an opcode.
  * Type system: Support explicit conversion of external function to address.
 
 Bugfixes:

docs/assembly.rst

@@ -248,6 +248,8 @@ In the grammar, opcodes are represented as pre-defined identifiers.
 +-------------------------+------+-----------------------------------------------------------------+
 | return(p, s)            | `-`  | end execution, return data mem[p..(p+s))                        |
 +-------------------------+------+-----------------------------------------------------------------+
+| revert(p, s)            | `-`  | end execution, revert state changes, return data mem[p..(p+s))  |
++-------------------------+------+-----------------------------------------------------------------+
 | selfdestruct(a)         | `-`  | end execution, destroy current contract and send funds to a     |
 +-------------------------+------+-----------------------------------------------------------------+
 | invalid                 | `-`  | end execution with invalid instruction                          |

docs/control-structures.rst

@@ -400,7 +400,7 @@ While a user-provided exception is generated in the following situations:
 #. Calling ``throw``.
 #. The condition of ``assert(condition)`` is not met.
 
-Internally, Solidity performs an "invalid jump" when a user-provided exception is thrown. In contrast, it performs an invalid operation
+Internally, Solidity performs a revert operation (instruction ``0xfd``) when a user-provided exception is thrown. In contrast, it performs an invalid operation
 (instruction ``0xfe``) if a runtime exception is encountered. In both cases, this causes
 the EVM to revert all changes made to the state. The reason for this is that there is no safe way to continue execution, because an expected effect
 did not occur. Because we want to retain the atomicity of transactions, the safest thing to do is to revert all changes and make the whole transaction

docs/miscellaneous.rst

@@ -435,7 +435,7 @@ The following is the order of precedence for operators, listed in order of evalu
 | *16*       | Comma operator                      | ``,``                                      |
 +------------+-------------------------------------+--------------------------------------------+
 
-.. index:: block, coinbase, difficulty, number, block;number, timestamp, block;timestamp, msg, data, gas, sender, value, now, gas price, origin, assert, keccak256, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send
+.. index:: block, coinbase, difficulty, number, block;number, timestamp, block;timestamp, msg, data, gas, sender, value, now, gas price, origin, assert, revert, keccak256, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send
 
 Global Variables
 ================
@@ -453,6 +453,7 @@ Global Variables
 - ``now`` (``uint``): current block timestamp (alias for ``block.timestamp``)
 - ``tx.gasprice`` (``uint``): gas price of the transaction
 - ``tx.origin`` (``address``): sender of the transaction (full call chain)
+- ``revert()``: abort execution and revert state changes
 - ``keccak256(...) returns (bytes32)``: compute the Ethereum-SHA-3 (Keccak-256) hash of the (tightly packed) arguments
 - ``sha3(...) returns (bytes32)``: an alias to `keccak256()`
 - ``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the (tightly packed) arguments

docs/units-and-global-variables.rst

@@ -79,7 +79,7 @@ Block and Transaction Properties
     You can only access the hashes of the most recent 256 blocks, all other
     values will be zero.
 
-.. index:: assert, keccak256, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send
+.. index:: assert, revert, keccak256, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send
 
 Mathematical and Cryptographic Functions
 ----------------------------------------
@@ -100,6 +100,8 @@ Mathematical and Cryptographic Functions
     compute RIPEMD-160 hash of the (tightly packed) arguments
 ``ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address)``:
     recover the address associated with the public key from elliptic curve signature or return zero on error
+``revert()``:
+    abort execution and revert state changes
 
 In the above, "tightly packed" means that the arguments are concatenated without padding.
 This means that the following are all identical::

libevmasm/GasMeter.cpp

@@ -80,6 +80,7 @@ GasMeter::GasConsumption GasMeter::estimateMax(AssemblyItem const& _item, bool _
 			gas += GasCosts::sloadGas;
 			break;
 		case Instruction::RETURN:
+		case Instruction::REVERT:
 			gas += memoryGas(0, -1);
 			break;
 		case Instruction::MLOAD:

libevmasm/Instruction.cpp

@@ -159,6 +159,7 @@ const std::map<std::string, Instruction> dev::solidity::c_instructions =
 	{ "CALLCODE", Instruction::CALLCODE },
 	{ "RETURN", Instruction::RETURN },
 	{ "DELEGATECALL", Instruction::DELEGATECALL },
+	{ "REVERT", Instruction::REVERT },
 	{ "INVALID", Instruction::INVALID },
 	{ "SELFDESTRUCT", Instruction::SELFDESTRUCT }
 };
@@ -294,6 +295,7 @@ static const std::map<Instruction, InstructionInfo> c_instructionInfo =
 	{ Instruction::CALLCODE,	{ "CALLCODE",		0, 7, 1, true, Tier::Special } },
 	{ Instruction::RETURN,		{ "RETURN",			0, 2, 0, true, Tier::Zero } },
 	{ Instruction::DELEGATECALL,	{ "DELEGATECALL",	0, 6, 1, true, Tier::Special } },
+	{ Instruction::REVERT,          { "REVERT",             0, 2, 0, true, Tier::Zero } },
 	{ Instruction::INVALID,		{ "INVALID",		0, 0, 0, true, Tier::Zero } },
 	{ Instruction::SELFDESTRUCT,	{ "SELFDESTRUCT",		0, 1, 0, true, Tier::Zero } }
 };

libevmasm/Instruction.h

@@ -177,6 +177,7 @@ enum class Instruction: uint8_t
 	RETURN,				///< halt execution returning output data
 	DELEGATECALL,		///< like CALLCODE but keeps caller's value and sender
 
+	REVERT = 0xfd,		///< halt execution, revert state and return output data
 	INVALID = 0xfe,		///< invalid instruction for expressing runtime errors (e.g., division-by-zero)
 	SELFDESTRUCT = 0xff	///< halt execution and register account for later deletion
 };

libevmasm/PeepholeOptimiser.cpp

@@ -200,7 +200,8 @@ struct UnreachableCode
 			it[0] != Instruction::RETURN &&
 			it[0] != Instruction::STOP &&
 			it[0] != Instruction::INVALID &&
-			it[0] != Instruction::SELFDESTRUCT
+			it[0] != Instruction::SELFDESTRUCT &&
+			it[0] != Instruction::REVERT
 		)
 			return false;
 

libevmasm/SemanticInformation.cpp

@@ -119,6 +119,7 @@ bool SemanticInformation::altersControlFlow(AssemblyItem const& _item)
 	case Instruction::SELFDESTRUCT:
 	case Instruction::STOP:
 	case Instruction::INVALID:
+	case Instruction::REVERT:
 		return true;
 	default:
 		return false;

libsolidity/analysis/GlobalContext.cpp

@@ -67,7 +67,9 @@ m_magicVariables(vector<shared_ptr<MagicVariableDeclaration const>>{make_shared<
 					make_shared<MagicVariableDeclaration>("ripemd160",
 							make_shared<FunctionType>(strings(), strings{"bytes20"}, FunctionType::Location::RIPEMD160, true)),
 					make_shared<MagicVariableDeclaration>("assert",
-							make_shared<FunctionType>(strings{"bool"}, strings{}, FunctionType::Location::Assert))})
+							make_shared<FunctionType>(strings{"bool"}, strings{}, FunctionType::Location::Assert)),
+					make_shared<MagicVariableDeclaration>("revert",
+							make_shared<FunctionType>(strings(), strings(), FunctionType::Location::Revert))})
 {
 }
 

libsolidity/ast/Types.cpp

@@ -2095,6 +2095,7 @@ string FunctionType::identifier() const
 	case Location::Send: id += "send"; break;
 	case Location::SHA3: id += "sha3"; break;
 	case Location::Selfdestruct: id += "selfdestruct"; break;
+	case Location::Revert: id += "revert"; break;
 	case Location::ECRecover: id += "ecrecover"; break;
 	case Location::SHA256: id += "sha256"; break;
 	case Location::RIPEMD160: id += "ripemd160"; break;

libsolidity/ast/Types.h

@@ -828,6 +828,7 @@ class FunctionType: public Type
 		Send, ///< CALL, but without data and gas
 		SHA3, ///< SHA3
 		Selfdestruct, ///< SELFDESTRUCT
+		Revert, ///< REVERT
 		ECRecover, ///< CALL to special contract for ecrecover
 		SHA256, ///< CALL to special contract for sha256
 		RIPEMD160, ///< CALL to special contract for ripemd160

libsolidity/codegen/ContractCompiler.cpp

@@ -762,7 +762,9 @@ bool ContractCompiler::visit(Return const& _return)
 bool ContractCompiler::visit(Throw const& _throw)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _throw);
-	m_context.appendJumpTo(m_context.errorTag());
+	// Do not send back an error detail.
+	m_context << u256(0) << u256(0);
+	m_context << Instruction::REVERT;
 	return false;
 }
 

libsolidity/codegen/ExpressionCompiler.cpp

@@ -650,6 +650,11 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			utils().convertType(*arguments.front()->annotation().type, *function.parameterTypes().front(), true);
 			m_context << Instruction::SELFDESTRUCT;
 			break;
+		case Location::Revert:
+			// memory offset returned - zero length
+			m_context << u256(0) << u256(0);
+			m_context << Instruction::REVERT;
+			break;
 		case Location::SHA3:
 		{
 			TypePointers argumentTypes;
@@ -867,8 +872,14 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 		{
 			arguments.front()->accept(*this);
 			utils().convertType(*arguments.front()->annotation().type, *function.parameterTypes().front(), false);
-			m_context << Instruction::ISZERO;
-			m_context.appendConditionalJumpTo(m_context.errorTag());
+			// jump if condition was met
+			m_context << Instruction::ISZERO << Instruction::ISZERO;
+			auto success = m_context.appendConditionalJump();
+			// condition was not met, abort
+			m_context << u256(0) << u256(0);
+			m_context << Instruction::REVERT;
+			// the success branch
+			m_context << success;
 			break;
 		}
 		default:

test/libsolidity/InlineAssembly.cpp

@@ -205,6 +205,11 @@ BOOST_AUTO_TEST_CASE(inline_assembly_shadowed_instruction_functional_assignment)
 	BOOST_CHECK(!successAssemble("{ gas := 2 }"));
 }
 
+BOOST_AUTO_TEST_CASE(revert)
+{
+	BOOST_CHECK(successAssemble("{ revert(0, 0) }"));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }

test/libsolidity/SolidityEndToEndTest.cpp

@@ -9102,6 +9102,30 @@ BOOST_AUTO_TEST_CASE(assert)
 	BOOST_CHECK(callContractFunction("g(bool)", true) == encodeArgs(true));
 }
 
+BOOST_AUTO_TEST_CASE(revert)
+{
+	char const* sourceCode = R"(
+		contract C {
+			uint public a = 42;
+			function f() {
+				a = 1;
+				revert();
+			}
+			function g() {
+				a = 1;
+				assembly {
+					revert(0, 0)
+				}
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "C");
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs());
+	BOOST_CHECK(callContractFunction("a()") == encodeArgs(u256(42)));
+	BOOST_CHECK(callContractFunction("g()") == encodeArgs());
+	BOOST_CHECK(callContractFunction("a()") == encodeArgs(u256(42)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }