From 4faa839813ce76fc87f99b002aad6cadd2b784e1 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Fri, 6 Apr 2018 15:14:55 +0200
Subject: Use error signature for revert data.

---
 libsolidity/codegen/CompilerUtils.cpp      | 14 ++++++++++++++
 libsolidity/codegen/CompilerUtils.h        |  7 +++++++
 libsolidity/codegen/ExpressionCompiler.cpp | 23 +++--------------------
 3 files changed, 24 insertions(+), 20 deletions(-)

(limited to 'libsolidity')

diff --git a/libsolidity/codegen/CompilerUtils.cpp b/libsolidity/codegen/CompilerUtils.cpp
index 34337d7d..b4550153 100644
--- a/libsolidity/codegen/CompilerUtils.cpp
+++ b/libsolidity/codegen/CompilerUtils.cpp
@@ -78,6 +78,20 @@ void CompilerUtils::toSizeAfterFreeMemoryPointer()
 	m_context << Instruction::SWAP1;
 }
 
+void CompilerUtils::revertWithStringData(Type const& _argumentType)
+{
+	solAssert(_argumentType.isImplicitlyConvertibleTo(*Type::fromElementaryTypeName("string memory")), "");
+	fetchFreeMemoryPointer();
+	m_context << (u256(FixedHash<4>::Arith(FixedHash<4>(dev::keccak256("Error(string)")))) << (256 - 32));
+	m_context << Instruction::DUP2 << Instruction::MSTORE;
+	m_context << u256(4) << Instruction::ADD;
+	// Stack: <string data> <mem pos of encoding start>
+	abiEncode({_argumentType.shared_from_this()}, {make_shared<ArrayType>(DataLocation::Memory, true)});
+	toSizeAfterFreeMemoryPointer();
+	m_context << Instruction::REVERT;
+	m_context.adjustStackOffset(_argumentType.sizeOnStack());
+}
+
 unsigned CompilerUtils::loadFromMemory(
 	unsigned _offset,
 	Type const& _type,
diff --git a/libsolidity/codegen/CompilerUtils.h b/libsolidity/codegen/CompilerUtils.h
index a32c5c6e..476a7559 100644
--- a/libsolidity/codegen/CompilerUtils.h
+++ b/libsolidity/codegen/CompilerUtils.h
@@ -54,6 +54,13 @@ public:
 	/// Stack post: <size> <mem_start>
 	void toSizeAfterFreeMemoryPointer();
 
+	/// Appends code that performs a revert, providing the given string data.
+	/// Will also append an error signature corresponding to Error(string).
+	/// @param _argumentType the type of the string argument, will be converted to memory string.
+	/// Stack pre: string data
+	/// Stack post:
+	void revertWithStringData(Type const& _argumentType);
+
 	/// Loads data from memory to the stack.
 	/// @param _offset offset in memory (or calldata)
 	/// @param _type data type to load
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index 3f521f2d..b67e7b68 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -685,17 +685,11 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 		{
 			if (!arguments.empty())
 			{
+				// function-sel(Error(string)) + encoding
 				solAssert(arguments.size() == 1, "");
 				solAssert(function.parameterTypes().size() == 1, "");
-				m_context << u256(0);
 				arguments.front()->accept(*this);
-				utils().fetchFreeMemoryPointer();
-				utils().abiEncode(
-					{make_shared<IntegerType>(256), arguments.front()->annotation().type},
-					{make_shared<IntegerType>(256), make_shared<ArrayType>(DataLocation::Memory, true)}
-				);
-				utils().toSizeAfterFreeMemoryPointer();
-				m_context << Instruction::REVERT;
+				utils().revertWithStringData(*arguments.front()->annotation().type);
 			}
 			else
 				m_context.appendRevert();
@@ -937,18 +931,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 				// condition was not met, flag an error
 				m_context.appendInvalid();
 			else if (arguments.size() > 1)
-			{
-				m_context << u256(0);
-				utils().moveIntoStack(arguments.at(1)->annotation().type->sizeOnStack(), 1);
-				utils().fetchFreeMemoryPointer();
-				utils().abiEncode(
-					{make_shared<IntegerType>(256), arguments.at(1)->annotation().type},
-					{make_shared<IntegerType>(256), make_shared<ArrayType>(DataLocation::Memory, true)}
-				);
-				utils().toSizeAfterFreeMemoryPointer();
-				m_context << Instruction::REVERT;
-				m_context.adjustStackOffset(arguments.at(1)->annotation().type->sizeOnStack());
-			}
+				utils().revertWithStringData(*arguments.at(1)->annotation().type);
 			else
 				m_context.appendRevert();
 			// the success branch
-- 
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