GXC Token smart contracts

GXC Token is ERC-20 token conforms following ERC-20 https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md

• name: 'Game X Coin'
• symbol: 'GXC'
• decimals: (uint8)18
• totalSupply: (uint256)1e27

• balanceOf: view (address) => (uint256)
• transfer: (address, uint256) => (bool)
• transferFrom: (address _from, address _to, uint256) => (bool)
• approve: (address, uint256) => (bool)
• allowance: (address _owner, address _spender) => (uint256)
• increaseApproval: (address _spender, uint256 _addedValue) => (bool)
• decreaseApproval: (address _spender, uint256 _subtractedValue) => (bool)

• Transfer(address indexed _from, address indexed _to, uint256 _value)
• Approval(address indexed _owner, address indexed _spender, uint256 _value)

There is an attack vector which exploits approve function to spend unwanted by spender. The discussion is here. Since EIP20 fixed its interface, so the suggestion of changing API isn't accepted.

Therefore, GXC token considers the work-around solution, hinted from MiniMeToken

The main idea of this, enforce token holder to call approve(spender, 0) before call it again with positive integer value. This is implemented here and tested here.

• Solidity v0.4.19 (solc or solc-js both work)
• Truffle v4.1.3 (core: 4.1.3)
• Node.js v8.11.1 (for dependency mgmt.)
• Docker (18.03.0-ce, build 0520e24, for oyente)

• install dependencies

$ yarn install --frozen-lockfile --production=false

• test command

$ truffle test

• forked from MVL Token