Correctly ignore costs of fallback for other functions.

3 files changed, 22 insertions, 1 deletions

diff --git a/Changelog.md b/Changelog.md
index 6df11f27..c6de5872 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -27,6 +27,7 @@ Bugfixes:
  * Code Generator: Treat empty base constructor argument list as not provided.
  * Commandline interface: Support ``--evm-version constantinople`` properly.
  * DocString Parser: Fix error message for empty descriptions.
+ * Gas Estimator: Correctly ignore costs of fallback function for other functions.
  * Standard JSON: Support ``constantinople`` as ``evmVersion`` properly.
  * Type Checker: Fix detection of recursive structs.
  * Type Checker: Fix asymmetry bug when comparing with literal numbers.
diff --git a/libsolidity/interface/GasEstimator.cpp b/libsolidity/interface/GasEstimator.cpp
index 2139395f..a496cc21 100644
--- a/libsolidity/interface/GasEstimator.cpp
+++ b/libsolidity/interface/GasEstimator.cpp
@@ -136,12 +136,19 @@ GasEstimator::GasConsumption GasEstimator::functionalEstimation(
 		ExpressionClasses& classes = state->expressionClasses();
 		using Id = ExpressionClasses::Id;
 		using Ids = vector<Id>;
+		// div(calldataload(0), 1 << 224) equals to hashValue
 		Id hashValue = classes.find(u256(FixedHash<4>::Arith(FixedHash<4>(dev::keccak256(_signature)))));
 		Id calldata = classes.find(Instruction::CALLDATALOAD, Ids{classes.find(u256(0))});
 		classes.forceEqual(hashValue, Instruction::DIV, Ids{
 			calldata,
-			classes.find(u256(1) << (8 * 28))
+			classes.find(u256(1) << 224)
 		});
+		// lt(calldatasize(), 4) equals to 0 (ignore the shortcut for fallback functions)
+		classes.forceEqual(
+			classes.find(u256(0)),
+			Instruction::LT,
+			Ids{classes.find(Instruction::CALLDATASIZE), classes.find(u256(4))}
+		);
 	}
 
 	PathGasMeter meter(_items, m_evmVersion);
diff --git a/test/libsolidity/GasMeter.cpp b/test/libsolidity/GasMeter.cpp
index fd2017f9..0d66456c 100644
--- a/test/libsolidity/GasMeter.cpp
+++ b/test/libsolidity/GasMeter.cpp
@@ -294,6 +294,19 @@ BOOST_AUTO_TEST_CASE(extcodesize_gas)
 	testRunTimeGas("f()", vector<bytes>{encodeArgs()});
 }
 
+BOOST_AUTO_TEST_CASE(regular_functions_exclude_fallback)
+{
+	// A bug in the estimator caused the costs for a specific function
+	// to always include the costs for the fallback.
+	char const* sourceCode = R"(
+		contract A {
+			uint public x;
+			function() { x = 2; }
+		}
+	)";
+	testCreationTimeGas(sourceCode);
+	testRunTimeGas("x()", vector<bytes>{encodeArgs()});
+}
 BOOST_AUTO_TEST_SUITE_END()
 
 }