jackCoin.sol

pragma solidity ^0.4.0;

import './Ownable.sol';

contract SimpleCoin is Ownable{
    
    string name;
    uint total;
    uint limit;
    mapping (address => uint) balances;
    
    constructor(string _name, uint _total, uint _limit) {
        total = _total;
        name = _name;
        limit = _limit;
        balances[msg.sender] = total;
    }
    
    modifier limitTransfer(uint _value) {
        assert(_value < limit);
        _;
    }
    
    function setLimit(uint _limit) onlyOwner public {
        LimitChanged(limit, _limit);
        limit = _limit;
    }
    
    function totalSupply() constant returns (uint256 ) {
        return total;
    }
    
    function balanceOf(address _owner) constant returns (uint256 ) {
        return balances[_owner];
    }

    function transfer(address _to, uint256 _value) limitTransfer(_value) returns (bool) {
        assert(_to != msg.sender);
        if (balances[msg.sender] >= _value) {
            balances[msg.sender] -= _value; // OVERFLOW CAN HAPPEN HERE
            balances[_to] += _value; // OVERFLOW CAN HAPPEN HERE
            emit Transfer(msg.sender, _to, _value);
        } else return false;
    }
    
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event LimitChanged(uint oldLimit, uint newLimit);
}