Add swarm hash to the end of the bytecode.

docs/miscellaneous.rst

@@ -242,14 +242,10 @@ It can be used to query the compiler version, the sourcecode, the ABI
 and NatSpec documentation in order to more safely interact with the contract
 and to verify its source code.
 
-The compiler inserts a swarm hash of that file into the bytecode of each
+The compiler appends a swarm hash (32 bytes) of that file to the end of the bytecode of each
 contract, so that you can retrieve the file in an authenticated way
 without having to resort to a centralized data provider.
 
-Specifically, the runtime code for a contract always starts with
-``push32 <metadata hash> pop``, so you can take a look at the 32 bytes starting at
-the second byte of the code of a contract.
-
 Of course, you have to publish the metadata file to swarm (or some other service)
 so that others can access it. The file can be output by using ``solc --metadata``.
 It will contain swarm references to the source code, so you have to upload
@@ -326,8 +322,7 @@ Usage for Automatic Interface Generation and NatSpec
 
 The metadata is used in the following way: A component that wants to interact
 with a contract (e.g. mist) retrieves the code of the contract
-and from that the first 33 bytes. If the first byte decodes into a PUSH32
-instruction, the other 32 bytes are interpreted as the swarm hash of
+and from that the last 32 bytes, which are interpreted as the swarm hash of
 a file which is then retrieved.
 That file is JSON-decoded into a structure like above.
 

libevmasm/Assembly.cpp

@@ -432,7 +432,7 @@ LinkerObject const& Assembly::assemble() const
 	unsigned bytesPerTag = dev::bytesRequired(bytesRequiredForCode);
 	byte tagPush = (byte)Instruction::PUSH1 - 1 + bytesPerTag;
 
-	unsigned bytesRequiredIncludingData = bytesRequiredForCode + 1;
+	unsigned bytesRequiredIncludingData = bytesRequiredForCode + 1 + m_auxiliaryData.size();
 	for (auto const& sub: m_subs)
 		bytesRequiredIncludingData += sub->assemble().bytecode.size();
 
@@ -525,8 +525,9 @@ LinkerObject const& Assembly::assemble() const
 		}
 	}
 
-	if (!dataRef.empty() && !subRef.empty())
-		ret.bytecode.push_back(0);
+	// Append a STOP just to be sure.
+	ret.bytecode.push_back(0);
+
 	for (size_t i = 0; i < m_subs.size(); ++i)
 	{
 		auto references = subRef.equal_range(i);
@@ -568,6 +569,9 @@ LinkerObject const& Assembly::assemble() const
 		}
 		ret.bytecode += dataItem.second;
 	}
+
+	ret.bytecode += m_auxiliaryData;
+
 	for (unsigned pos: sizeRef)
 	{
 		bytesRef r(ret.bytecode.data() + pos, bytesPerDataRef);

libevmasm/Assembly.h

@@ -71,6 +71,9 @@ public:
 	AssemblyItem appendJumpI(AssemblyItem const& _tag) { auto ret = append(_tag.pushTag()); append(solidity::Instruction::JUMPI); return ret; }
 	AssemblyItem errorTag() { return AssemblyItem(PushTag, 0); }
 
+	/// Appends @a _data literally to the very end of the bytecode.
+	void appendAuxiliaryDataToEnd(bytes const& _data) { m_auxiliaryData += _data; }
+
 	template <class T> Assembly& operator<<(T const& _d) { append(_d); return *this; }
 	AssemblyItems const& items() const { return m_items; }
 	AssemblyItem const& back() const { return m_items.back(); }
@@ -125,10 +128,12 @@ private:
 	Json::Value createJsonValue(std::string _name, int _begin, int _end, std::string _value = std::string(), std::string _jumpType = std::string()) const;
 
 protected:
-	// 0 is reserved for exception
+	/// 0 is reserved for exception
 	unsigned m_usedTags = 1;
 	AssemblyItems m_items;
 	std::map<h256, bytes> m_data;
+	/// Data that is appended to the very end of the contract.
+	bytes m_auxiliaryData;
 	std::vector<std::shared_ptr<Assembly>> m_subs;
 	std::map<h256, std::string> m_strings;
 	std::map<h256, std::string> m_libraries; ///< Identifiers of libraries to be linked.

libsolidity/ast/AST.cpp

@@ -65,6 +65,7 @@ SourceUnitAnnotation& SourceUnit::annotation() const
 
 string Declaration::sourceUnitName() const
 {
+	solAssert(!!m_scope, "");
 	ASTNode const* scope = m_scope;
 	while (dynamic_cast<Declaration const*>(scope) && dynamic_cast<Declaration const*>(scope)->m_scope)
 		scope = dynamic_cast<Declaration const*>(scope)->m_scope;

libsolidity/codegen/Compiler.cpp

@@ -36,6 +36,7 @@ void Compiler::compileContract(
 {
 	ContractCompiler runtimeCompiler(nullptr, m_runtimeContext, m_optimize);
 	runtimeCompiler.compileContract(_contract, _contracts);
+	m_runtimeContext.appendAuxiliaryData(_metadataHash.asBytes());
 
 	// This might modify m_runtimeContext because it can access runtime functions at
 	// creation time.
@@ -43,9 +44,6 @@ void Compiler::compileContract(
 	m_runtimeSub = creationCompiler.compileConstructor(_contract, _contracts);
 
 	m_context.optimise(m_optimize, m_optimizeRuns);
-
-	solAssert(m_runtimeSub != size_t(-1), "");
-	m_context.injectMetadataHashIntoSub(m_runtimeSub, _metadataHash);
 }
 
 void Compiler::compileClone(

libsolidity/codegen/CompilerContext.cpp

@@ -227,13 +227,6 @@ void CompilerContext::injectVersionStampIntoSub(size_t _subIndex)
 	sub.injectStart(fromBigEndian<u256>(binaryVersion()));
 }
 
-void CompilerContext::injectMetadataHashIntoSub(size_t _subIndex, h256 const& _metadataHash)
-{
-	eth::Assembly& sub = m_asm->sub(_subIndex);
-	sub.injectStart(Instruction::POP);
-	sub.injectStart(u256(_metadataHash));
-}
-
 FunctionDefinition const& CompilerContext::resolveVirtualFunction(
 	FunctionDefinition const& _function,
 	vector<ContractDefinition const*>::const_iterator _searchStart

libsolidity/codegen/CompilerContext.h

@@ -155,8 +155,8 @@ public:
 	/// Prepends "PUSH <compiler version number> POP"
 	void injectVersionStampIntoSub(size_t _subIndex);
 
-	/// Prepends "PUSH <metadata hash> POP"
-	void injectMetadataHashIntoSub(size_t _subIndex, h256 const& _metadataHash);
+	/// Appends arbitrary data to the end of the bytecode.
+	void appendAuxiliaryData(bytes const& _data) { m_asm->appendAuxiliaryDataToEnd(_data); }
 
 	void optimise(bool _fullOptimsation, unsigned _runs = 200) { m_asm->optimise(_fullOptimsation, true, _runs); }
 

libsolidity/interface/CompilerStack.cpp

@@ -375,6 +375,7 @@ Json::Value const& CompilerStack::metadata(Contract const& _contract, Documentat
 	if (!m_parseSuccessful)
 		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Parsing was not successful."));
 
+	solAssert(_contract.contract, "");
 	std::unique_ptr<Json::Value const>* doc;
 
 	// checks wheather we already have the documentation