Merge pull request #4428 from ethereum/enforce_staticcall_view

[BREAKING] Enforce STATICCALL for view and pure

Changelog.md

@@ -10,6 +10,7 @@ Breaking Changes:
  * ABI Encoder: Properly pad data from calldata (``msg.data`` and external function parameters). Use ``abi.encodePacked`` for unpadded encoding.
  * Code Generator: Signed right shift uses proper arithmetic shift, i.e. rounding towards negative infinity. Warning: this may silently change the semantics of existing code!
  * Code Generator: Revert at runtime if calldata is too short or points out of bounds. This is done inside the ``ABI decoder`` and therefore also applies to ``abi.decode()``.
+ * Code Generator: Use ``STATICCALL`` for ``pure`` and ``view`` functions. This was already the case in the experimental 0.5.0 mode.
  * Commandline interface: Remove obsolete ``--formal`` option.
  * Commandline interface: Rename the ``--julia`` option to ``--yul``.
  * Commandline interface: Require ``-`` if standard input is used as source.

docs/contracts.rst

@@ -451,6 +451,10 @@ View Functions
 
 Functions can be declared ``view`` in which case they promise not to modify the state.
 
+.. note::
+  If the compiler's EVM target is Byzantium or newer (default) the opcode
+  ``STATICCALL`` is used.
+
 The following statements are considered modifying the state:
 
 #. Writing to state variables.
@@ -464,7 +468,7 @@ The following statements are considered modifying the state:
 
 ::
 
-    pragma solidity ^0.4.16;
+    pragma solidity >0.4.24;
 
     contract C {
         function f(uint a, uint b) public view returns (uint) {
@@ -479,11 +483,12 @@ The following statements are considered modifying the state:
   Getter methods are marked ``view``.
 
 .. note::
-  If invalid explicit type conversions are used, state modifications are possible
-  even though a ``view`` function was called.
-  You can switch the compiler to use ``STATICCALL`` when calling such functions and thus
-  prevent modifications to the state on the level of the EVM by adding
-  ``pragma experimental "v0.5.0";``
+  Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
+  for ``view`` functions.
+  This enabled state modifications in ``view`` functions through the use of
+  invalid explicit type conversions.
+  By using  ``STATICCALL`` for ``view`` functions, modifications to the
+  state are prevented on the level of the EVM.
 
 .. index:: ! pure function, function;pure
 
@@ -494,6 +499,9 @@ Pure Functions
 
 Functions can be declared ``pure`` in which case they promise not to read from or modify the state.
 
+.. note::
+  If the compiler's EVM target is Byzantium or newer (default) the opcode ``STATICCALL`` is used.
+
 In addition to the list of state modifying statements explained above, the following are considered reading from the state:
 
 #. Reading from state variables.
@@ -504,7 +512,7 @@ In addition to the list of state modifying statements explained above, the follo
 
 ::
 
-    pragma solidity ^0.4.16;
+    pragma solidity >0.4.24;
 
     contract C {
         function f(uint a, uint b) public pure returns (uint) {
@@ -513,11 +521,12 @@ In addition to the list of state modifying statements explained above, the follo
     }
 
 .. note::
-  If invalid explicit type conversions are used, state modifications are possible
-  even though a ``pure`` function was called.
-  You can switch the compiler to use ``STATICCALL`` when calling such functions and thus
-  prevent modifications to the state on the level of the EVM by adding
-  ``pragma experimental "v0.5.0";``
+  Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
+  for ``pure`` functions.
+  This enabled state modifications in ``pure`` functions through the use of
+  invalid explicit type conversions.
+  By using  ``STATICCALL`` for ``pure`` functions, modifications to the
+  state are prevented on the level of the EVM.
 
 .. warning::
   It is not possible to prevent functions from reading the state at the level

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1810,15 +1810,11 @@ void ExpressionCompiler::appendExternalFunctionCall(
 	if (_functionType.bound())
 		utils().moveToStackTop(gasValueSize, _functionType.selfType()->sizeOnStack());
 
-	bool const v050 = m_context.experimentalFeatureActive(ExperimentalFeature::V050);
 	auto funKind = _functionType.kind();
 	bool returnSuccessCondition = funKind == FunctionType::Kind::BareCall || funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::BareDelegateCall;
 	bool isCallCode = funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::CallCode;
 	bool isDelegateCall = funKind == FunctionType::Kind::BareDelegateCall || funKind == FunctionType::Kind::DelegateCall;
-	bool useStaticCall =
-		_functionType.stateMutability() <= StateMutability::View &&
-		v050 &&
-		m_context.evmVersion().hasStaticCall();
+	bool useStaticCall = _functionType.stateMutability() <= StateMutability::View && m_context.evmVersion().hasStaticCall();
 
 	bool haveReturndatacopy = m_context.evmVersion().supportsReturndata();
 	unsigned retSize = 0;

test/libsolidity/SolidityEndToEndTest.cpp

@@ -12487,7 +12487,6 @@ BOOST_AUTO_TEST_CASE(abi_encode_call)
 BOOST_AUTO_TEST_CASE(staticcall_for_view_and_pure)
 {
 	char const* sourceCode = R"(
-		pragma experimental "v0.5.0";
 		contract C {
 			uint x;
 			function f() public returns (uint) {
@@ -12722,6 +12721,43 @@ BOOST_AUTO_TEST_CASE(senders_balance)
 	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(27)));
 }
 
+BOOST_AUTO_TEST_CASE(write_storage_external)
+{
+	char const* sourceCode = R"(
+		contract C {
+			uint public x;
+			function f(uint y) public payable {
+				x = y;
+			}
+			function g(uint y) external {
+				x = y;
+			}
+			function h() public {
+				this.g(12);
+			}
+		}
+		contract D {
+			C c = new C();
+			function f() public payable returns (uint) {
+				c.g(3);
+				return c.x();
+			}
+			function g() public returns (uint) {
+				c.g(8);
+				return c.x();
+			}
+			function h() public returns (uint) {
+				c.h();
+				return c.x();
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "D");
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(3));
+	ABI_CHECK(callContractFunction("g()"), encodeArgs(8));
+	ABI_CHECK(callContractFunction("h()"), encodeArgs(12));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }