overflowUnderflow.sol

/* Bad */
pragma solidity =0.4.11;
contract Bad {
  mapping(address => uint256) balances;
  function badWithdraw(uint256 amounts) public {
  require(amounts <= balances[msg.sender]);
  balances[msg.sender] -= amounts; 
  (bool success, bytes memory data) = msg.sender.call{value: amounts}(""); 
  require(success);
  }
}
/* Better */
pragma solidity =0.8.0; // only version change
contract Good {
  mapping(address => uint256) balances;
  function badWithdraw(uint256 amounts) public {
  require(amounts <= balances[msg.sender]);
  balances[msg.sender] -= amounts;
  (bool success, bytes memory data) = msg.sender.call{value: amounts}(""); 
  require(success);
  }
}