Merge pull request #2679 from ethereum/delegatecall

.delegatecall() should always return a boolean of execution status

Changelog.md

@@ -3,6 +3,7 @@
 Features:
 
 Bugfixes:
+ * Code Generator: ``.delegatecall()`` should always return execution outcome.
  * Code Generator: Provide "new account gas" for low-level ``callcode`` and ``delegatecall``.
 
 ### 0.4.14 (2017-07-31)

docs/bugs.json

@@ -1,4 +1,12 @@
 [
+    {
+        "name": "DelegateCallReturnValue",
+        "summary": "The low-level .delegatecall() does not return the execution outcome, but converts the value returned by the functioned called to a boolean instead.",
+        "description": "The return value of the low-level .delegatecall() function is taken from a position in memory, where the call data or the return data resides. This value is interpreted as a boolean and put onto the stack. This means if the called function returns at least 32 zero bytes, .delegatecall() returns false even if the call was successuful.",
+        "introduced": "0.3.0",
+        "fixed": "0.4.15",
+        "severity": "low"
+    },
     {
         "name": "ECRecoverMalformedInput",
         "summary": "The ecrecover() builtin can return garbage for malformed input.",

docs/bugs_by_version.json

@@ -182,6 +182,7 @@
     }, 
     "0.3.0": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -198,6 +199,7 @@
     }, 
     "0.3.1": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -213,6 +215,7 @@
     }, 
     "0.3.2": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -228,6 +231,7 @@
     }, 
     "0.3.3": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -242,6 +246,7 @@
     }, 
     "0.3.4": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -256,6 +261,7 @@
     }, 
     "0.3.5": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -270,6 +276,7 @@
     }, 
     "0.3.6": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -282,6 +289,7 @@
     }, 
     "0.4.0": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -294,6 +302,7 @@
     }, 
     "0.4.1": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -306,6 +315,7 @@
     }, 
     "0.4.10": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
@@ -314,6 +324,7 @@
     }, 
     "0.4.11": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral"
         ], 
@@ -321,22 +332,27 @@
     }, 
     "0.4.12": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput"
         ], 
         "released": "2017-07-03"
     }, 
     "0.4.13": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput"
         ], 
         "released": "2017-07-06"
     }, 
     "0.4.14": {
-        "bugs": [], 
+        "bugs": [
+            "DelegateCallReturnValue"
+        ], 
         "released": "2017-07-31"
     }, 
     "0.4.2": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -348,6 +364,7 @@
     }, 
     "0.4.3": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -358,6 +375,7 @@
     }, 
     "0.4.4": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -367,6 +385,7 @@
     }, 
     "0.4.5": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -377,6 +396,7 @@
     }, 
     "0.4.6": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
@@ -386,6 +406,7 @@
     }, 
     "0.4.7": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
@@ -394,6 +415,7 @@
     }, 
     "0.4.8": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
@@ -402,6 +424,7 @@
     }, 
     "0.4.9": {
         "bugs": [
+            "DelegateCallReturnValue", 
             "ECRecoverMalformedInput", 
             "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"

docs/control-structures.rst

@@ -393,6 +393,9 @@ When exceptions happen in a sub-call, they "bubble up" (i.e. exceptions are reth
 and the low-level functions ``call``, ``delegatecall`` and ``callcode`` -- those return ``false`` in case
 of an exception instead of "bubbling up".
 
+.. warning::
+    The low-level ``call``, ``delegatecall`` and ``callcode`` will return success if the calling account is non-existent, as part of the design of EVM. Existence must be checked prior to calling if desired.
+
 Catching exceptions is not yet possible.
 
 In the following example, you can see how ``require`` can be used to easily check conditions on inputs

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1560,7 +1560,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
 		utils().moveToStackTop(gasValueSize, _functionType.selfType()->sizeOnStack());
 
 	auto funKind = _functionType.kind();
-	bool returnSuccessCondition = funKind == FunctionType::Kind::BareCall || funKind == FunctionType::Kind::BareCallCode;
+	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;
 

test/libsolidity/SolidityEndToEndTest.cpp

@@ -9897,6 +9897,64 @@ BOOST_AUTO_TEST_CASE(inlineasm_empty_let)
 	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(0), u256(0)));
 }
 
+BOOST_AUTO_TEST_CASE(bare_call_invalid_address)
+{
+	char const* sourceCode = R"(
+		contract C {
+			/// Calling into non-existant account is successful (creates the account)
+			function f() external constant returns (bool) {
+				return address(0x4242).call();
+			}
+			function g() external constant returns (bool) {
+				return address(0x4242).callcode();
+			}
+			function h() external constant returns (bool) {
+				return address(0x4242).delegatecall();
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "C");
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("g()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("h()") == encodeArgs(u256(1)));
+}
+
+BOOST_AUTO_TEST_CASE(delegatecall_return_value)
+{
+	char const* sourceCode = R"DELIMITER(
+		contract C {
+			uint value;
+			function set(uint _value) external {
+				value = _value;
+			}
+			function get() external constant returns (uint) {
+				return value;
+			}
+			function get_delegated() external constant returns (bool) {
+				return this.delegatecall(bytes4(sha3("get()")));
+			}
+			function assert0() external constant {
+				assert(value == 0);
+			}
+			function assert0_delegated() external constant returns (bool) {
+				return this.delegatecall(bytes4(sha3("assert0()")));
+			}
+		}
+	)DELIMITER";
+	compileAndRun(sourceCode, 0, "C");
+	BOOST_CHECK(callContractFunction("get()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("assert0_delegated()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("get_delegated()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("set(uint256)", u256(1)) == encodeArgs());
+	BOOST_CHECK(callContractFunction("get()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("assert0_delegated()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("get_delegated()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("set(uint256)", u256(42)) == encodeArgs());
+	BOOST_CHECK(callContractFunction("get()") == encodeArgs(u256(42)));
+	BOOST_CHECK(callContractFunction("assert0_delegated()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("get_delegated()") == encodeArgs(u256(1)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }