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Merge pull request #4415 from ethereum/uninitializedStoragePointer

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[BREAKING] Turn uninitialized storage variables into error.
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chriseth 2018-07-10 15:24:01 +02:00 committed by GitHub
commit 7650905567
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12 changed files with 31 additions and 84 deletions
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1
Changelog.md
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@ -34,6 +34,7 @@ Breaking Changes:
* Type Checker: Disallow arithmetic operations for boolean variables.
* Type Checker: Disallow conversions between ``bytesX`` and ``uintY`` of different size.
* Type Checker: Disallow specifying base constructor arguments multiple times in the same inheritance hierarchy. This was already the case in the experimental 0.5.0 mode.
* Type Checker: Disallow uninitialized storage variables. This was already the case in the experimental 0.5.0 mode.
* Type Checker: Only accept a single ``bytes`` type for ``.call()`` (and family), ``keccak256()``, ``sha256()`` and ``ripemd160()``.
* Remove obsolete ``std`` directory from the Solidity repository. This means accessing ``https://github.com/ethereum/soldity/blob/develop/std/*.sol`` (or ``https://github.com/ethereum/solidity/std/*.sol`` in Remix) will not be possible.
* Syntax Checker: Named return values in function types are an error.

47
docs/frequently-asked-questions.rst
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@ -306,48 +306,11 @@ independent copy of the state variable is created in memory and
is another issue). The modifications to this independent copy do not
carry back to ``data1`` or ``data2``.
A common mistake is to declare a local variable and assume that it will
be created in memory, although it will be created in storage::
/// THIS CONTRACT CONTAINS AN ERROR
pragma solidity ^0.4.0;
contract C {
uint someVariable;
uint[] data;
function f() public {
uint[] x;
x.push(2);
data = x;
}
}
The type of the local variable ``x`` is ``uint[] storage``, but since
storage is not dynamically allocated, it has to be assigned from
a state variable before it can be used. So no space in storage will be
allocated for ``x``, but instead it functions only as an alias for
a pre-existing variable in storage.
What will happen is that the compiler interprets ``x`` as a storage
pointer and will make it point to the storage slot ``0`` by default.
This has the effect that ``someVariable`` (which resides at storage
slot ``0``) is modified by ``x.push(2)``.
The correct way to do this is the following::
pragma solidity ^0.4.0;
contract C {
uint someVariable;
uint[] data;
function f() public {
uint[] x = data;
x.push(2);
}
}
.. warning::
Prior to version 0.5.0, a common mistake was to declare a local variable and assume that it will
be created in memory, although it will be created in storage. Using such a variable without initializing
it could lead to unexpected behavior. Starting from 0.5.0, however, storage variables have to be initialized,
which should prevent these kinds of mistakes.
******************
Advanced Questions

5
libsolidity/analysis/TypeChecker.cpp
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@ -1073,10 +1073,7 @@ bool TypeChecker::visit(VariableDeclarationStatement const& _statement)
if (varDecl.referenceLocation() == VariableDeclaration::Location::Default)
errorText += " Did you mean '<type> memory " + varDecl.name() + "'?";
solAssert(m_scope, "");
if (v050)
m_errorReporter.declarationError(varDecl.location(), errorText);
else
m_errorReporter.warning(varDecl.location(), errorText);
m_errorReporter.declarationError(varDecl.location(), errorText);
}
}
else if (dynamic_cast<MappingType const*>(type(varDecl).get()))

7
test/libsolidity/SolidityEndToEndTest.cpp
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@ -7878,6 +7878,7 @@ BOOST_AUTO_TEST_CASE(tuples)
char const* sourceCode = R"(
contract C {
uint[] data;
uint[] m_c;
function g() internal returns (uint a, uint b, uint[] storage c) {
return (1, 2, data);
}
@ -7890,7 +7891,7 @@ BOOST_AUTO_TEST_CASE(tuples)
uint a; uint b;
(a, b) = this.h();
if (a != 5 || b != 6) return 1;
uint[] storage c;
uint[] storage c = m_c;
(a, b, c) = g();
if (a != 1 || b != 2 || c[0] != 3) return 2;
(a, b) = (b, a);
@ -9585,7 +9586,7 @@ BOOST_AUTO_TEST_CASE(calling_uninitialized_function_through_array)
{ assembly { mstore(0, 7) return(0, 0x20) } }
mutex = 1;
// Avoid re-executing this function if we jump somewhere.
function() internal returns (uint)[200] x;
function() internal returns (uint)[200] memory x;
x[0]();
return 2;
}
@ -10113,7 +10114,7 @@ BOOST_AUTO_TEST_CASE(copy_internal_function_array_to_storage)
function() internal returns (uint)[20] x;
int mutex;
function one() public returns (uint) {
function() internal returns (uint)[20] xmem;
function() internal returns (uint)[20] memory xmem;
x = xmem;
return 3;
}

9
test/libsolidity/syntaxTests/array/uninitialized_storage_var.sol Normal file
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@ -0,0 +1,9 @@
contract C {
function f() {
uint[] storage x;
uint[10] storage y;
}
}
// ----
// DeclarationError: (31-47): Uninitialized storage pointer.
// DeclarationError: (51-69): Uninitialized storage pointer.

10
test/libsolidity/syntaxTests/nameAndTypeResolution/206_storage_location_local_variables.sol
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@ -1,11 +1,9 @@
contract C {
function f() public {
uint[] storage x;
uint[] m_x;
function f() public view {
uint[] storage x = m_x;
uint[] memory y;
uint[] memory z;
x;y;z;
x;y;
}
}
// ----
// Warning: (47-63): Uninitialized storage pointer.
// Warning: (17-135): Function state mutability can be restricted to pure

2
test/libsolidity/syntaxTests/nameAndTypeResolution/211_uninitialized_mapping_array_variable.sol
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@ -5,4 +5,4 @@ contract C {
}
}
// ----
// Warning: (52-85): Uninitialized storage pointer.
// DeclarationError: (52-85): Uninitialized storage pointer.

9
test/libsolidity/syntaxTests/nameAndTypeResolution/212_uninitialized_mapping_array_variable_050.sol
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@ -1,9 +0,0 @@
pragma experimental "v0.5.0";
contract C {
function f() pure public {
mapping(uint => uint)[] storage x;
x;
}
}
// ----
// DeclarationError: (82-115): Uninitialized storage pointer.

2
test/libsolidity/syntaxTests/nameAndTypeResolution/233_non_initialized_references.sol
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@ -8,4 +8,4 @@ contract C {
}
}
// ----
// Warning: (84-95): Uninitialized storage pointer.
// DeclarationError: (84-95): Uninitialized storage pointer.

11
test/libsolidity/syntaxTests/nameAndTypeResolution/234_non_initialized_references_050.sol
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@ -1,11 +0,0 @@
pragma experimental "v0.5.0";
contract C {
struct s {
uint a;
}
function f() public {
s storage x;
}
}
// ----
// DeclarationError: (114-125): Uninitialized storage pointer.

2
test/libsolidity/syntaxTests/parsing/arrays_in_expressions.sol
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@ -5,4 +5,4 @@ contract c {
// Warning: (39-46): Variable is declared as a storage pointer. Use an explicit "storage" keyword to silence this warning.
// Warning: (52-67): Variable is declared as a storage pointer. Use an explicit "storage" keyword to silence this warning.
// TypeError: (39-50): Type int_const 7 is not implicitly convertible to expected type contract c[10] storage pointer.
// Warning: (52-67): Uninitialized storage pointer. Did you mean '<type> memory x'?
// DeclarationError: (52-67): Uninitialized storage pointer. Did you mean '<type> memory x'?

10
test/libsolidity/syntaxTests/parsing/location_specifiers_for_locals.sol
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@ -1,11 +1,9 @@
contract Foo {
function f() public {
uint[] storage x;
uint[] m_x;
function f() public view {
uint[] storage x = m_x;
uint[] memory y;
x; y;
}
}
// ----
// Warning: (49-65): Uninitialized storage pointer.
// Warning: (49-65): Unused local variable.
// Warning: (75-90): Unused local variable.
// Warning: (19-97): Function state mutability can be restricted to pure