cerc-io/solidity
16
0
Fork 0
mirror of https://github.com/ethereum/solidity synced 2023-10-03 13:03:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

050 breaking changes in docs

Browse Source
This commit is contained in:
Leonardo Alt 2018-09-04 12:46:59 +02:00
parent 63c6007012
commit 13d8645506
2 changed files with 407 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

406
docs/050-breaking-changes.rst Normal file
View File

@ -0,0 +1,406 @@
********************************
Solidity v0.5.0 Breaking Changes
********************************
This section highlights the main breaking changes introduced in Solidity
version 0.5.0, along with the reasoning behind the changes and how to update
affected code.
For the full list check
`the release changelog <https://github.com/ethereum/solidity/releases/tag/v0.5.0>`_.
.. note::
Contracts compiled with Solidity v0.5.0 can still interface with contracts
and even libraries compiled with older versions without recompiling or
redeploying them. Changing the interfaces to include data locations and
visibility and mutability specifiers suffices.
Semantic Only Changes
=====================
This section lists the changes that are semantic-only, thus potentially
hiding new and different behavior in existing code.
* Signed right shift now uses proper arithmetic shift, i.e. rounding towards
negative infinity, instead of rounding towards zero. Signed and unsigned
shift will have dedicated opcodes in Constantinople, and are emulated by
Solidity for the moment.
* The ``continue`` statement in a ``do...while`` loop now jumps to the
condition, which is the common behavior in such cases. It used to jump to the
loop body. Thus, if the condition is false, the loop terminates.
* The functions ``.call()``, ``.delegatecall()`` and ``.staticcall()`` do not
pad anymore when given a single ``bytes`` parameter.
* Pure and view functions are now called using the opcode ``STATICCALL``
instead of ``CALL`` if the EVM version is Byzantium or later. This
disallows state changes on the EVM level.
* The ABI encoder now properly pads byte arrays and strings from calldata
(``msg.data`` and external function parameters) when used in external
function calls and in ``abi.encode``. For unpadded encoding, use
``abi.encodePacked``.
* The ABI decoder reverts in the beginning of functions and in
``abi.decode()`` if passed calldata is too short or points out of bounds.
Note that dirty higher order bits are still simply ignored.
* Forward all available gas with external function calls starting from
tangerine whistle.
Semantic and Syntactic Changes
==============================
This section highlights changes that affect syntax and semantics.
* The functions ``.call()``, ``.delegatecall()`, ``staticcall()``,
``keccak256()``, ``sha256()`` and ``ripemd160()`` now accept only a single
``bytes`` argument. Moreover, the argument is not padded. This was changed to
make more explicit and clear how the arguments are concatenated. Change every
``.call()`` (and family) to a ``.call("")`` and every ``.call(signature, a,
b, c)`` to use ``.call(abi.encodeWithSignature(signature, a, b, c))`` (the
last one only works for value types). Change every ``keccak256(a, b, c)`` to
``keccak256(abi.encodePacked(a, b, c))``. Even though it is not a breaking
change, it is suggested that developers change
``x.call(bytes4(keccak256("f(uint256)"), a, b)`` to
``x.call(abi.encodeWithSignature("f(uint256)", a, b))``.
* Functions ``.call()``, ``.delegatecall()`` and ``.staticcall()`` now return
``(bool, bytes memory)`` to provide access to the return data. Change
``bool success = otherContract.call("f")`` to ``(bool success, bytes memory
data) = otherContract.call("f")``.
* Solidity now implements C99-style scoping rules for function local
variables, that is, variables can only be used after they have been
declared and only in the same or nested scopes. Variables declared in the
initialization block of a ``for`` loop are valid at any point inside the
loop.
Explicitness Requirements
=========================
This section lists changes where the code now needs to be more explicit.
For most of the topics the compiler will provide suggestions.
* Explicit function visibility is now mandatory. Add ``public`` to every
function and constructor, and ``external`` to every fallback or interface
function that does not specify its visibility already.
* Explicit data location for all variables of struct, array or mapping types is
now mandatory. This is also applied to function parameters and return
variables. For example, change ``uint[] x = m_x`` to ``uint[] storage x =
m_x``, and ``function f(uint[][] x)`` to ``function f(uint[][] memory x)``
where ``memory`` is the data location and might be replaced by ``storage`` or
``calldata`` accordingly. Note that ``external`` functions require
parameters with a data location of ``calldata``.
* Contract types do not include ``address`` members anymore in
order to separate the namespaces. Therefore, it is now necessary to
explicitly convert values of contract type to addresses before using an
``address`` member. Example: if ``c`` is a contract, change
``c.transfer(...)`` to ``address(c).transfer(...)``,
and ``c.balance`` to ``address(c).balance``.
* The ``address`` type was split into ``address`` and ``address payable``,
where only ``address payable`` provides the ``transfer`` function. An
``address payable`` can be directly converted to an ``address``, but the
other way around is not allowed. Converting ``address`` to ``address
payable`` is possible via conversion through ``uint160``. If ``c`` is
a contract, ``address(c)`` results in ``address payable`` if ``c`` has a
payable fallback function.
* Conversions between ``bytesX`` and ``uintY`` of different size are now
disallowed due to ``bytesX`` padding on the right and ``uintY`` padding on
the left which may cause unexpected conversion results. The size must now be
adjusted within the type before the conversion. For example, you can convert
a ``bytes4`` (4 bytes) to a ``uint64`` (8 bytes) by first converting the
``bytes4`` variable to ``bytes8`` and then to ``uint64``. You get the
opposite padding when converting through ``uint32``.
* Using ``msg.value`` in non-payable functions (or introducing it via a
modifier) is disallowed as a security feature. Turn the function into
``payable`` or create a new internal function for the program logic that
uses ``msg.value``.
* For clarity reasons, the command line interface now requires ``-`` if the
standard input is used as source.
Deprecated Elements
===================
This section lists changes that deprecate prior features or syntax. Note that
many of these changes were already enabled in the experimental mode
``v0.5.0``.
Command Line and JSON Interfaces
--------------------------------
* The command line option ``--formal`` (used to generate Why3 output for
further formal verification) was deprecated and is now removed. A new
formal verification module, the SMTChecker, is enabled via ``pragma
experimental SMTChecker;``.
* The command line option ``--julia`` was renamed to ``--yul`` due to the
renaming of the intermediate language ``Julia`` to ``Yul``.
* The ``--clone-bin`` and ``--combined-json clone-bin`` command line options
were removed.
* Remappings with empty prefix are disallowed.
* The Json AST fields ``constant`` and ``payable`` were removed. The
information is now present in the ``stateMutability`` field.
Constructors
------------
* Constructors must now be defined using the ``constructor`` keyword.
* Calling base constructors without parentheses is now disallowed.
* Specifying base constructor arguments multiple times in the same inheritance
hierarchy is now disallowed.
* Calling a constructor with arguments but with wrong argument count is now
disallowed. If you only want to specify an inheritance relation without
giving arguments, do not provide parentheses at all.
Functions
---------
* Function ``callcode`` is now disallowed (in favor of ``delegatecall``). It
is still possible to use it via inline assembly.
* ``suicide`` is now disallowed (in favor of ``selfdestruct``).
* ``sha3`` is now disallowed (in favor of ``keccak256``).
* ``throw`` is now disallowed (in favor of ``revert``, ``require`` and
``assert``).
Conversions
-----------
* Explicit and implicit conversions from decimal literals to ``bytesXX`` types
is now disallowed.
* Explicit and implicit conversions from hex literals to ``bytesXX`` types
of different size is now disallowed.
Literals and Suffixes
---------------------
* The unit denomination ``years`` is now disallowed due to complications and
confusions about leap years.
* Trailing dots that are not followed by a number are now disallowed.
* Combining hex numbers with unit denominations (e.g. ``0x1e wei``) is now
disallowed.
Variables
---------
* Declaring empty structs is now disallowed for clarity.
* The ``var`` keyword is now disallowed to favor explicitness.
* Assignments between tuples with different number of components is now
disallowed.
* Values for constants that are not compile-time constants are disallowed.
* Multi-variable declarations with mismatching number of values are now
disallowed.
* Uninitialized storage variables are now disallowed.
* Empty tuple components are now disallowed.
* Detecting cyclic dependencies in variables and structs is limited in
recursion to 256.
Syntax
------
* Using ``constant`` as function state mutability modifier is now disallowed.
* Boolean expressions cannot use arithmetic operations.
* The unary ``+`` operator is now disallowed.
* Literals cannot anymore be used with ``abi.encodePacked`` without prior
conversion to an explicit type.
* Empty return statements for functions with one or more return values are now
disallowed.
* The "loose assembly" syntax is now disallowed entirely, that is, jump labels,
jumps and non-functional instructions cannot be used anymore. Use the new
``while``, ``switch`` and ``if`` constructs instead.
* Functions without implementation cannot use modifiers anymore.
* Function types with named return values are now disallowed.
* Single statement variable declarations inside if/while/for bodies that are
not blocks are now disallowed.
* New keywords: ``calldata`` and ``constructor``.
* New reserved keywords: ``alias``, ``apply``, ``auto``, ``copyof``,
``define``, ``immutable``, ``implements``, ``macro``, ``mutable``,
``override``, ``partial``, ``promise``, ``reference``, ``sealed``,
``sizeof``, ``supports``, ``typedef`` and ``unchecked``.
Example
=======
The following example shows a contract and its updated version for Solidity
v0.5.0 with some of the changes listed in this section.
Old version:
::
// This will not compile
pragma solidity ^0.4.25;
contract OtherContract {
uint x;
function f(uint y) external {
x = y;
}
function() payable external {}
}
contract Old {
OtherContract other;
uint myNumber;
// Function mutability not provided, not an error.
function someInteger() internal returns (uint) { return 2; }
// Function visibility not provided, not an error.
// Function mutability not provided, not an error.
function f(uint x) returns (bytes) {
// Var is fine in this version.
var z = someInteger();
x += z;
// Throw is fine in this version.
if (x > 100)
throw;
bytes b = new bytes(x);
y = -3 >> 1;
// y == -1 (wrong, should be -2)
do {
x += 1;
if (x > 10) continue;
// 'Continue' causes an infinite loop.
} while (x < 11);
// Call returns only a Bool.
bool success = address(other).call("f");
if (!success)
revert();
else {
// Local variables could be declared after their use.
int y;
}
return b;
}
// No need for an explicit data location for 'arr'
function g(uint[] arr, bytes8 x, OtherContract otherContract) public {
otherContract.transfer(1 ether);
// Since uint32 (4 bytes) is smaller than bytes8 (8 bytes),
// the first 4 bytes of x will be lost. This might lead to
// unexpected behavior since bytesX are right padded.
uint32 y = uint32(x);
myNumber += y + msg.value;
}
}
New version:
::
pragma solidity >0.4.25;
contract OtherContract {
uint x;
function f(uint y) external {
x = y;
}
function() payable external {}
}
contract New {
OtherContract other;
uint myNumber;
// Function mutability must be specified.
function someInteger() internal pure returns (uint) { return 2; }
// Function visibility must be specified.
// Function mutability must be specified.
function f(uint x) public returns (bytes memory) {
// The type must now be explicitly given.
uint z = someInteger();
x += z;
// Throw is now disallowed.
require(x > 100);
int y = -3 >> 1;
// y == -2 (correct)
do {
x += 1;
if (x > 10) continue;
// 'Continue' jumps to the condition below.
} while (x < 11);
// Call returns (bool, bytes).
// Data location must be specified.
(bool success, bytes memory data) = address(other).call("f");
if (!success)
revert();
return data;
}
using address_make_payable for address;
// Data location for 'arr' must be specified
function g(uint[] memory arr, bytes8 x, OtherContract otherContract, address unknownContract) public payable {
// 'otherContract.transfer' is not provided.
// Since the code of 'OtherContract' is known and has the fallback
// function, address(otherContract) has type 'address payable'.
address(otherContract).transfer(1 ether);
// 'unknownContract.transfer' is not provided.
// 'address(unknownContract).transfer' is not provided
// since 'address(unknownContract)' is not 'address payable'.
// If the function takes an 'address' which you want to send
// funds to, you can convert it to 'address payable' via 'uint160'.
// Note: This is not recommended and the explicit type
// 'address payable' should be used whenever possible.
// To increase clarity, we suggest the use of a library for
// the conversion (provided after the contract in this example).
address payable addr = unknownContract.make_payable();
require(addr.send(1 ether));
// Since uint32 (4 bytes) is smaller than bytes8 (8 bytes),
// the conversion is not allowed.
// We need to convert to a common size first:
bytes4 x4 = bytes4(x); // Padding happens on the right
uint32 y = uint32(x4); // Conversion is consistent
// 'msg.value' cannot be used in a 'non-payable' function.
// We need to make the function payable
myNumber += y + msg.value;
}
}
// We can define a library for explicitly converting ``address``
// to ``address payable`` as a workaround.
library address_make_payable {
function make_payable(address x) internal pure returns (address payable) {
return address(uint160(x));
}
}

1
docs/solidity-in-depth.rst
View File

@ -18,3 +18,4 @@ If something is missing here, please contact us on
contracts.rst
assembly.rst
miscellaneous.rst
050-breaking-changes.rst