ethereum · chriseth · Oct 19, 2020 · chriseth · Oct 19, 2020 · chriseth
diff --git a/libsolidity/codegen/CompilerContext.h b/libsolidity/codegen/CompilerContext.h
diff --git a/libsolidity/codegen/ContractCompiler.cpp b/libsolidity/codegen/ContractCompiler.cpp
diff --git a/libsolidity/codegen/ContractCompiler.cpp b/libsolidity/codegen/ContractCompiler.cpp
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
diff --git a/docs/grammar/Solidity.g4 b/docs/grammar/Solidity.g4
+block:
+	LBrace ( statement | uncheckedBlock )* RBrace;
+
+uncheckedBlock: Unchecked block;
diff --git a/docs/types/value-types.rst b/docs/types/value-types.rst
+  There are two modes in which arithmetic is performed on these types: The "wrapping" or "unchecked" mode and the "checked" mode.
+  By default, arithmetic is always "checked", which mean that if the result of an operation falls outside the value range
+  of the type, the call is reverted through a :ref:`failing assertion<assert-and-require>`. You can switch to "unchecked" mode
+  using ``unchecked { ... }``. More details can be found in the section about <unchecked>.
diff --git a/docs/types/value-types.rst b/docs/types/value-types.rst
+modes in regard to over- and underflow:
+
+By default, all arithmetic is checked for under- or overflow, but this can be disabled
+using the <unchecked> block, resulting in wrapping arithmetic. More details
-using the <unchecked> block, resulting in wrapping arithmetic. More details
+using the <unchecked> block, resulting in modular arithmetic. More details
diff --git a/libsolidity/codegen/CompilerContext.h b/libsolidity/codegen/CompilerContext.h
@@ -380,6 +384,8 @@ class CompilerContext
 	std::map<Declaration const*, std::vector<unsigned>> m_localVariables;
 	/// The contract currently being compiled. Virtual function lookup starts from this contarct.
 	ContractDefinition const* m_mostDerivedContract = nullptr;
+	/// Whether to use checked arithmetic.
+	std::stack<Arithmetic> m_arithmetic;
diff --git a/docs/control-structures.rst b/docs/control-structures.rst
+An overflow or underflow is the situation where the resulting value of an arithmetic operation,
+when executed on an unrestricted integer, falls outside the range of the result type.
diff --git a/docs/grammar/Solidity.g4 b/docs/grammar/Solidity.g4
+block:
+	LBrace ( statement | uncheckedBlock )* RBrace;
+
+uncheckedBlock: Unchecked block;
diff --git a/docs/grammar/Solidity.g4 b/docs/grammar/Solidity.g4
+block:
+	LBrace ( statement | uncheckedBlock )* RBrace;
+
+uncheckedBlock: Unchecked block;
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -460,7 +479,7 @@ bool ExpressionCompiler::visit(BinaryOperation const& _binaryOperation)
 		m_context << commonType->literalValue(nullptr);
 	else
 	{
-		bool cleanupNeeded = cleanupNeededForOp(commonType->category(), c_op);
+		bool cleanupNeeded = m_context.arithmetic() == Arithmetic::Checked || cleanupNeededForOp(commonType->category(), c_op);
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -275,7 +275,7 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 		solAssert(*_assignment.annotation().type == leftType, "");
 	bool cleanupNeeded = false;
 	if (op != Token::Assign)
-		cleanupNeeded = cleanupNeededForOp(leftType.category(), binOp);
+		cleanupNeeded = m_context.arithmetic() == Arithmetic::Checked || cleanupNeededForOp(leftType.category(), binOp);
diff --git a/libsolidity/codegen/YulUtilFunctions.cpp b/libsolidity/codegen/YulUtilFunctions.cpp
+	});
+}
+
+
diff --git a/libsolidity/codegen/ir/IRGeneratorForStatements.cpp b/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
 				break;
 			case Token::Mod:
-				fun = m_utils.checkedIntModFunction(*type);
+				fun = m_utils.intModFunction(*type);
diff --git a/test/libsolidity/SolidityParser.cpp b/test/libsolidity/SolidityParser.cpp
 	BOOST_CHECK(TokenTraits::isReservedKeyword(Token::Var));
+	BOOST_CHECK(TokenTraits::isReservedKeyword(Token::Reference));
	using the <unchecked> block, resulting in wrapping arithmetic. More details
	using the <unchecked> block, resulting in modular arithmetic. More details
		An overflow or underflow is the situation where the resulting value of an arithmetic operation,
		when executed on an unrestricted integer, falls outside the range of the result type.
		BOOST_CHECK(TokenTraits::isReservedKeyword(Token::Var));
		BOOST_CHECK(TokenTraits::isReservedKeyword(Token::Reference));