Allocate one byte per memory byte array element instead of 32.

3 files changed, 34 insertions, 2 deletions

diff --git a/Changelog.md b/Changelog.md
index c8ea21f5..ed3cdfea 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -13,6 +13,7 @@ Features:
  * Type Checker: Require ``storage`` or ``memory`` keyword for local variables as experimental 0.5.0 feature.
 
 Bugfixes:
+ * Code Generator: Allocate one byte per memory byte array element instead of 32.
  * Optimizer: Remove unused stack computation results.
  * Parser: Fix source location of VariableDeclarationStatement.
  * Type Checker: Properly check array length and don't rely on an assertion in code generation.
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index fe37baac..bb8c4a94 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -858,8 +858,15 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			m_context << Instruction::DUP1 << Instruction::DUP3 << Instruction::MSTORE;
 			// Stack: memptr requested_length
 			// update free memory pointer
-			m_context << Instruction::DUP1 << arrayType.baseType()->memoryHeadSize();
-			m_context << Instruction::MUL << u256(32) << Instruction::ADD;
+			m_context << Instruction::DUP1;
+			// Stack: memptr requested_length requested_length
+			if (arrayType.isByteArray())
+				// Round up to multiple of 32
+				m_context << u256(31) << Instruction::ADD << u256(31) << Instruction::NOT << Instruction::AND;
+			else
+				m_context << arrayType.baseType()->memoryHeadSize() << Instruction::MUL;
+			// stacK: memptr requested_length data_size
+			m_context << u256(32) << Instruction::ADD;
 			m_context << Instruction::DUP3 << Instruction::ADD;
 			utils().storeFreeMemoryPointer();
 			// Stack: memptr requested_length
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index ac77a7e1..648c13cb 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -7309,6 +7309,30 @@ BOOST_AUTO_TEST_CASE(create_memory_array)
 	ABI_CHECK(callContractFunction("f()"), encodeArgs(string("A"), u256(8), u256(4), string("B")));
 }
 
+BOOST_AUTO_TEST_CASE(create_memory_array_allocation_size)
+{
+	// Check allocation size of byte array. Should be 32 plus length rounded up to next
+	// multiple of 32
+	char const* sourceCode = R"(
+		contract C {
+			function f() pure returns (uint d1, uint d2, uint d3) {
+				bytes memory b1 = new bytes(31);
+				bytes memory b2 = new bytes(32);
+				bytes memory b3 = new bytes(256);
+				bytes memory b4 = new bytes(31);
+				assembly {
+					d1 := sub(b2, b1)
+					d2 := sub(b3, b2)
+					d3 := sub(b4, b3)
+				}
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(0x40, 0x40, 0x20 + 256));
+}
+
+
 BOOST_AUTO_TEST_CASE(memory_arrays_of_various_sizes)
 {
 	// Computes binomial coefficients the chinese way