Merge pull request #756 from chriseth/alloczero

Bugfix: Allocate empty array.

3 files changed, 21 insertions, 3 deletions

diff --git a/libsolidity/codegen/CompilerUtils.h b/libsolidity/codegen/CompilerUtils.h
index 55254013..da74dc90 100644
--- a/libsolidity/codegen/CompilerUtils.h
+++ b/libsolidity/codegen/CompilerUtils.h
@@ -104,6 +104,7 @@ public:
 	);
 
 	/// Zero-initialises (the data part of) an already allocated memory array.
+	/// Length has to be nonzero!
 	/// Stack pre: <length> <memptr>
 	/// Stack post: <updated_memptr>
 	void zeroInitialiseMemoryArray(ArrayType const& _type);
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index b973a117..80009a90 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -792,15 +792,18 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			utils().storeFreeMemoryPointer();
 			// Stack: memptr requested_length
 
+			// Check if length is zero
+			m_context << Instruction::DUP1 << Instruction::ISZERO;
+			auto skipInit = m_context.appendConditionalJump();
+
 			// We only have to initialise if the base type is a not a value type.
 			if (dynamic_cast<ReferenceType const*>(arrayType.baseType().get()))
 			{
 				m_context << Instruction::DUP2 << u256(32) << Instruction::ADD;
 				utils().zeroInitialiseMemoryArray(arrayType);
-				m_context << Instruction::POP;
 			}
-			else
-				m_context << Instruction::POP;
+			m_context << skipInit;
+			m_context << Instruction::POP;
 			break;
 		}
 		default:
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index 8dcc878e..4b634649 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -6837,6 +6837,20 @@ BOOST_AUTO_TEST_CASE(skip_dynamic_types_for_structs)
 	BOOST_CHECK(callContractFunction("g()") == encodeArgs(u256(2), u256(6)));
 }
 
+BOOST_AUTO_TEST_CASE(create_dynamic_array_with_zero_length)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f() returns (uint) {
+				var a = new uint[][](0);
+				return 7;
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "C");
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(7)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }