Merge pull request #2452 from ethereum/fixPassingEmptyString

Fix passing empty string

5 files changed, 64 insertions, 2 deletions

diff --git a/Changelog.md b/Changelog.md
index fdba5a46..6f0d76d6 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -16,6 +16,7 @@ Bugfixes:
  * Type Checker: Make UTF8-validation a bit more sloppy to include more valid sequences.
  * Fixed crash concerning non-callable types.
  * Unused variable warnings no longer issued for variables used inside inline assembly.
+ * Code Generator: Fix ABI encoding of empty literal string.
  * Inline Assembly: Enforce function arguments when parsing functional instructions.
  * Fixed segfault with constant function parameters
 
diff --git a/docs/bugs.json b/docs/bugs.json
index 1a67d626..a0c0e7c4 100644
--- a/docs/bugs.json
+++ b/docs/bugs.json
@@ -1,5 +1,12 @@
 [
     {
+        "name": "SkipEmptyStringLiteral",
+	"summary": "If \"\" is used in a function call, the following function arguments will not be correctly passed to the function.",
+        "description": "If the empty string literal \"\" is used as an argument in a function call, it is skipped by the encoder. This has the effect that the encoding of all arguments following this is shifted left by 32 bytes and thus the function call data is corrupted.",
+        "fixed": "0.4.12",
+        "severity": "low"
+    },
+    {
         "name": "ConstantOptimizerSubtraction",
         "summary": "In some situations, the optimizer replaces certain numbers in the code with routines that compute different numbers.",
         "description": "The optimizer tries to represent any number in the bytecode by routines that compute them with less gas. For some special numbers, an incorrect routine is generated. This could allow an attacker to e.g. trick victims about a specific amount of ether, or function calls to call different functions (or none at all).",
diff --git a/docs/bugs_by_version.json b/docs/bugs_by_version.json
index 0f7346b4..1be05f3c 100644
--- a/docs/bugs_by_version.json
+++ b/docs/bugs_by_version.json
@@ -1,6 +1,7 @@
 {
     "0.1.0": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -15,6 +16,7 @@
     }, 
     "0.1.1": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -29,6 +31,7 @@
     }, 
     "0.1.2": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -43,6 +46,7 @@
     }, 
     "0.1.3": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -57,6 +61,7 @@
     }, 
     "0.1.4": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -71,6 +76,7 @@
     }, 
     "0.1.5": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStaleKnowledgeAboutSHA3", 
@@ -85,6 +91,7 @@
     }, 
     "0.1.6": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -100,6 +107,7 @@
     }, 
     "0.1.7": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -115,6 +123,7 @@
     }, 
     "0.2.0": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -130,6 +139,7 @@
     }, 
     "0.2.1": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -145,6 +155,7 @@
     }, 
     "0.2.2": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -160,6 +171,7 @@
     }, 
     "0.3.0": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -174,6 +186,7 @@
     }, 
     "0.3.1": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -187,6 +200,7 @@
     }, 
     "0.3.2": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -200,6 +214,7 @@
     }, 
     "0.3.3": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -212,6 +227,7 @@
     }, 
     "0.3.4": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -224,6 +240,7 @@
     }, 
     "0.3.5": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -236,6 +253,7 @@
     }, 
     "0.3.6": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -246,6 +264,7 @@
     }, 
     "0.4.0": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -256,6 +275,7 @@
     }, 
     "0.4.1": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -266,16 +286,20 @@
     }, 
     "0.4.10": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
         ], 
         "released": "2017-03-15"
     }, 
     "0.4.11": {
-        "bugs": [], 
+        "bugs": [
+            "SkipEmptyStringLiteral"
+        ], 
         "released": "2017-05-03"
     }, 
     "0.4.2": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage", 
@@ -285,6 +309,7 @@
     }, 
     "0.4.3": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "HighOrderByteCleanStorage"
@@ -293,6 +318,7 @@
     }, 
     "0.4.4": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored"
         ], 
@@ -300,6 +326,7 @@
     }, 
     "0.4.5": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored", 
             "OptimizerStateKnowledgeNotResetForJumpdest"
@@ -308,6 +335,7 @@
     }, 
     "0.4.6": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction", 
             "IdentityPrecompileReturnIgnored"
         ], 
@@ -315,18 +343,21 @@
     }, 
     "0.4.7": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
         ], 
         "released": "2016-12-15"
     }, 
     "0.4.8": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
         ], 
         "released": "2017-01-13"
     }, 
     "0.4.9": {
         "bugs": [
+            "SkipEmptyStringLiteral", 
             "ConstantOptimizerSubtraction"
         ], 
         "released": "2017-01-31"
diff --git a/libsolidity/codegen/CompilerUtils.cpp b/libsolidity/codegen/CompilerUtils.cpp
index 3baaaddf..bfe72961 100644
--- a/libsolidity/codegen/CompilerUtils.cpp
+++ b/libsolidity/codegen/CompilerUtils.cpp
@@ -128,7 +128,7 @@ void CompilerUtils::storeInMemoryDynamic(Type const& _type, bool _padToWordBound
 		m_context << Instruction::DUP1;
 		storeStringData(bytesConstRef(str->value()));
 		if (_padToWordBoundaries)
-			m_context << u256(((str->value().size() + 31) / 32) * 32);
+			m_context << u256(max<size_t>(32, ((str->value().size() + 31) / 32) * 32));
 		else
 			m_context << u256(str->value().size());
 		m_context << Instruction::ADD;
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index ba507e0c..823a8eda 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -9469,6 +9469,29 @@ BOOST_AUTO_TEST_CASE(revert)
 	BOOST_CHECK(callContractFunction("a()") == encodeArgs(u256(42)));
 }
 
+BOOST_AUTO_TEST_CASE(literal_empty_string)
+{
+	char const* sourceCode = R"(
+		contract C {
+			bytes32 public x;
+			uint public a;
+			function f(bytes32 _x, uint _a) {
+				x = _x;
+				a = _a;
+			}
+			function g() {
+				this.f("", 2);
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "C");
+	BOOST_CHECK(callContractFunction("x()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("a()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("g()") == encodeArgs());
+	BOOST_CHECK(callContractFunction("x()") == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("a()") == encodeArgs(u256(2)));
+}
+
 BOOST_AUTO_TEST_CASE(scientific_notation)
 {
 	char const* sourceCode = R"(