Merge pull request #5061 from ethereum/fixedSizeArrayLength

Disallow fixed-size arrays with zero length

Changelog.md

@@ -84,6 +84,7 @@ Language Features:
  * General: Allow ``mapping`` storage pointers as arguments and return values in all internal functions.
  * General: Allow ``struct``s in interfaces.
  * General: Provide access to the ABI decoder through ``abi.decode(bytes memory data, (...))``.
+ * General: Disallow zero length for fixed-size arrays.
  * Parser: Accept the ``address payable`` type during parsing.
 
 Compiler Features:
@@ -101,6 +102,7 @@ Bugfixes:
  * Tests: Fix chain parameters to make ipc tests work with newer versions of cpp-ethereum.
  * Code Generator: Fix allocation of byte arrays (zeroed out too much memory).
  * Code Generator: Properly handle negative number literals in ABIEncoderV2.
+ * Code Generator: Do not crash on using a length of zero for multidimensional fixed-size arrays.
  * Commandline Interface: Correctly handle paths with backslashes on windows.
  * Fix NatSpec json output for `@notice` and `@dev` tags on contract definitions.
  * Optimizer: Correctly estimate gas costs of constants for special cases.

docs/050-breaking-changes.rst

@@ -222,6 +222,8 @@ Variables
 * Detecting cyclic dependencies in variables and structs is limited in
   recursion to 256.
 
+* Fixed-size arrays with a length of zero are now disallowed.
+
 Syntax
 ------
 

libsolidity/analysis/ReferencesResolver.cpp

@@ -246,6 +246,8 @@ void ReferencesResolver::endVisit(ArrayTypeName const& _typeName)
 		RationalNumberType const* lengthType = dynamic_cast<RationalNumberType const*>(lengthTypeGeneric.get());
 		if (!lengthType || !lengthType->mobileType())
 			fatalTypeError(length->location(), "Invalid array length, expected integer literal or constant expression.");
+		else if (lengthType->isZero())
+			fatalTypeError(length->location(), "Array with zero length specified.");
 		else if (lengthType->isFractional())
 			fatalTypeError(length->location(), "Array with fractional length specified.");
 		else if (lengthType->isNegative())

test/libsolidity/syntaxTests/array/length/fixed_size_multidim_zero_length.sol

@@ -0,0 +1,15 @@
+contract C {
+  function a() public pure returns(int[0][500] memory) {}
+  function b() public pure returns(uint[0][500] memory) {}
+  function c() public pure returns(byte[0][500] memory) {}
+  function d() public pure returns(bytes32[0][500] memory) {}
+  function e() public pure returns(bytes[0][500] memory) {}
+  function e() public pure returns(string[0][500] memory) {}
+}
+// ----
+// TypeError: (52-53): Array with zero length specified.
+// TypeError: (111-112): Array with zero length specified.
+// TypeError: (170-171): Array with zero length specified.
+// TypeError: (232-233): Array with zero length specified.
+// TypeError: (292-293): Array with zero length specified.
+// TypeError: (353-354): Array with zero length specified.

test/libsolidity/syntaxTests/array/length/fixed_size_zero_length.sol

@@ -0,0 +1,15 @@
+contract C {
+  int[0] a;
+  uint[0] b;
+  byte[0] c;
+  bytes32[0] d;
+  bytes[0] e;
+  string[0] f;
+}
+// ----
+// TypeError: (19-20): Array with zero length specified.
+// TypeError: (32-33): Array with zero length specified.
+// TypeError: (45-46): Array with zero length specified.
+// TypeError: (61-62): Array with zero length specified.
+// TypeError: (75-76): Array with zero length specified.
+// TypeError: (90-91): Array with zero length specified.

test/libsolidity/syntaxTests/array/length/parentheses.sol

@@ -21,5 +21,5 @@ contract C {
     uint[((2) + 1) + 1] a12;
     uint[(2 + 1) + ((1))] a13;
     uint[(((2) + 1)) + (((1)))] a14;
-    uint[((((2) + 1)) + (((1))))%1] a15;
+    uint[((((3) + 1)) + (((1))))%2] a15;
 }

test/libsolidity/syntaxTests/parsing/arrays_in_storage.sol

@@ -1,6 +1,6 @@
 contract c {
     uint[10] a;
     uint[] a2;
-    struct x { uint[2**20] b; y[0] c; }
+    struct x { uint[2**20] b; y[1] c; }
     struct y { uint d; mapping(uint=>x)[] e; }
 }