From e16d88c894aca5aae90bfc094906d2c138534296 Mon Sep 17 00:00:00 2001
From: Christian <c@ethdev.com>
Date: Wed, 14 Jan 2015 10:16:58 +0100
Subject: [PATCH] Check for hash collisions already before compiling.

---
 libsolidity/AST.cpp                    | 38 ++++++++++++++++++++------
 libsolidity/AST.h                      |  2 ++
 test/SolidityNameAndTypeResolution.cpp | 12 ++++++++
 3 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index d171006a8..ea8ecdb75 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -50,18 +50,27 @@ void ContractDefinition::checkTypeRequirements()
 
 	for (ASTPointer<FunctionDefinition> const& function: getDefinedFunctions())
 		function->checkTypeRequirements();
+
+	// check for hash collisions in function signatures
+	vector<pair<FixedHash<4>, FunctionDefinition const*>> exportedFunctionList = getInterfaceFunctionList();
+	set<FixedHash<4>> hashes;
+	for (auto const& hashAndFunction: getInterfaceFunctionList())
+	{
+		FixedHash<4> const& hash = hashAndFunction.first;
+		if (hashes.count(hash))
+			BOOST_THROW_EXCEPTION(createTypeError("Function signature hash collision for " +
+												  hashAndFunction.second->getCanonicalSignature()));
+		hashes.insert(hash);
+	}
 }
 
 map<FixedHash<4>, FunctionDefinition const*> ContractDefinition::getInterfaceFunctions() const
 {
-	map<FixedHash<4>, FunctionDefinition const*> exportedFunctions;
-	for (ASTPointer<FunctionDefinition> const& f: m_definedFunctions)
-		if (f->isPublic() && f->getName() != getName())
-		{
-			FixedHash<4> hash(dev::sha3(f->getCanonicalSignature()));
-			auto res = exportedFunctions.insert(std::make_pair(hash,f.get()));
-			solAssert(res.second, "Hash collision at Function Definition Hash calculation");
-		}
+	vector<pair<FixedHash<4>, FunctionDefinition const*>> exportedFunctionList = getInterfaceFunctionList();
+	map<FixedHash<4>, FunctionDefinition const*> exportedFunctions(exportedFunctionList.begin(),
+																   exportedFunctionList.end());
+	solAssert(exportedFunctionList.size() == exportedFunctions.size(),
+			  "Hash collision at Function Definition Hash calculation");
 
 	return exportedFunctions;
 }
@@ -74,6 +83,19 @@ FunctionDefinition const* ContractDefinition::getConstructor() const
 	return nullptr;
 }
 
+vector<pair<FixedHash<4>, FunctionDefinition const*>> ContractDefinition::getInterfaceFunctionList() const
+{
+	vector<pair<FixedHash<4>, FunctionDefinition const*>> exportedFunctions;
+	for (ASTPointer<FunctionDefinition> const& f: m_definedFunctions)
+		if (f->isPublic() && f->getName() != getName())
+		{
+			FixedHash<4> hash(dev::sha3(f->getCanonicalSignature()));
+			exportedFunctions.push_back(make_pair(hash, f.get()));
+		}
+
+	return exportedFunctions;
+}
+
 void StructDefinition::checkMemberTypes() const
 {
 	for (ASTPointer<VariableDeclaration> const& member: getMembers())
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index 95121d4cb..28fb7f0a5 100755
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -191,6 +191,8 @@ public:
 	FunctionDefinition const* getConstructor() const;
 
 private:
+	std::vector<std::pair<FixedHash<4>, FunctionDefinition const*>> getInterfaceFunctionList() const;
+
 	std::vector<ASTPointer<StructDefinition>> m_definedStructs;
 	std::vector<ASTPointer<VariableDeclaration>> m_stateVariables;
 	std::vector<ASTPointer<FunctionDefinition>> m_definedFunctions;
diff --git a/test/SolidityNameAndTypeResolution.cpp b/test/SolidityNameAndTypeResolution.cpp
index 94271b1f7..e2b4f160d 100644
--- a/test/SolidityNameAndTypeResolution.cpp
+++ b/test/SolidityNameAndTypeResolution.cpp
@@ -357,6 +357,18 @@ BOOST_AUTO_TEST_CASE(function_canonical_signature_type_aliases)
 		}
 }
 
+
+BOOST_AUTO_TEST_CASE(hash_collision_in_interface)
+{
+	char const* text = "contract test {\n"
+					   "  function gsf() {\n"
+					   "  }\n"
+					   "  function tgeo() {\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }