Add SB Curated (copied from the smartbugs repository).

dataset/front_running/ERC20.sol

@@ -0,0 +1,129 @@
+/*
+ * @source: https://github.com/SmartContractSecurity/SWC-registry/blob/master/test_cases/transaction_order_dependence/ERC20.sol
+ * @author: -
+ * @vulnerable_at_lines: 110,113
+ */
+
+pragma solidity ^0.4.24;
+
+/** Taken from the OpenZeppelin github
+ * @title SafeMath
+ * @dev Math operations with safety checks that revert on error
+ */
+library SafeMath {
+
+  /**
+  * @dev Multiplies two numbers, reverts on overflow.
+  */
+  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+    // benefit is lost if 'b' is also tested.
+    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+    if (a == 0) {
+      return 0;
+    }
+
+    uint256 c = a * b;
+    require(c / a == b);
+
+    return c;
+  }
+
+  /**
+  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
+  */
+  function div(uint256 a, uint256 b) internal pure returns (uint256) {
+    require(b > 0); // Solidity only automatically asserts when dividing by 0
+    uint256 c = a / b;
+    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+
+    return c;
+  }
+
+  /**
+  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
+  */
+  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+    require(b <= a);
+    uint256 c = a - b;
+
+    return c;
+  }
+
+  /**
+  * @dev Adds two numbers, reverts on overflow.
+  */
+  function add(uint256 a, uint256 b) internal pure returns (uint256) {
+    uint256 c = a + b;
+    require(c >= a);
+
+    return c;
+  }
+
+  /**
+  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
+  * reverts when dividing by zero.
+  */
+  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
+    require(b != 0);
+    return a % b;
+  }
+}
+
+
+contract ERC20 {
+
+  event Transfer( address indexed from, address indexed to, uint256 value );
+  event Approval( address indexed owner, address indexed spender, uint256 value);
+  using SafeMath for *;
+
+  mapping (address => uint256) private _balances;
+
+  mapping (address => mapping (address => uint256)) private _allowed;
+
+  uint256 private _totalSupply;
+
+  constructor(uint totalSupply){
+    _balances[msg.sender] = totalSupply;
+  }
+
+  function balanceOf(address owner) public view returns (uint256) {
+    return _balances[owner];
+  }
+
+
+  function allowance(address owner, address spender) public view returns (uint256)
+  {
+    return _allowed[owner][spender];
+  }
+
+  function transfer(address to, uint256 value) public returns (bool) {
+    require(value <= _balances[msg.sender]);
+    require(to != address(0));
+
+    _balances[msg.sender] = _balances[msg.sender].sub(value);
+    _balances[to] = _balances[to].add(value);
+    emit Transfer(msg.sender, to, value);
+    return true;
+  }
+  // <yes> <report> FRONT_RUNNING
+  function approve(address spender, uint256 value) public returns (bool) {
+    require(spender != address(0));
+     // <yes> <report> FRONT_RUNNING
+    _allowed[msg.sender][spender] = value;
+    emit Approval(msg.sender, spender, value);
+    return true;
+  }
+
+  function transferFrom(address from, address to, uint256 value) public returns (bool) {
+    require(value <= _balances[from]);
+    require(value <= _allowed[from][msg.sender]);
+    require(to != address(0));
+
+    _balances[from] = _balances[from].sub(value);
+    _balances[to] = _balances[to].add(value);
+    _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
+    emit Transfer(from, to, value);
+    return true;
+  }
+}