SafeMath阻止合同初始化？

Question

我正在通过Remix和Metamask部署。

我正在使用这个SafeMath函数，它似乎阻止了我的合同初始化它的所有状态变量(契约部署，但是所有的vars都是零)：

function add(uint256 a, uint256 b) internal constant returns (uint256) {
  uint256 c = a + b;
  assert(c >= a);
  return c;
}

库函数似乎导致了以下函数中的问题。要明确的是，下面的deposit函数甚至在部署期间都没有被调用。但是，当我使用启用if块(使用.add SafeMath公式)中的第一行部署合同时，契约会部署，但没有设置任何状态变量。

当我使用第二行时，一切都很好。

我是否不正确地使用SafeMath库？

function deposit(address addr) payable {

  uint256 amt = msg.value;

  uint alreadyDeposited = deposits[addr]; // deposits is an address => uint mapping

  if (alreadyDeposited > 0) {
    // deposits[addr] = alreadyDeposited.add(amt); // When this line is enabled, my contract doesn't initialize (for example, "ownerWallet", which should be msg.sender, is not set when the contract deploys).
    deposits[addr] = alreadyDeposited + amt; // this line lets contract vars initialize appropriately.
  }

  sendFunds();
}

有人能解释一下add如何知道如何使用自己作为第一个参数吗？

Answer 1

我认为这个错误来自于您的if代码，当调用deposite函数时，地址存储的值为零，因为无法初始化地址的值。我去掉if条件，一切都好。这是我的测试代码，如下：

pragma solidity ^0.4.13;

import "./SafeMath.sol";

contract Test{

    using SafeMath for uint;
    mapping (address => uint) deposits;

    function deposit(address addr) payable {
        uint256 amt = msg.value;
        uint alreadyDeposited = deposits[addr]; // deposits is an address => uint mapping
        // if (alreadyDeposited > 0) {
            deposits[addr] =  alreadyDeposited.add(amt);// When this line is enabled, my contract doesn't initialize (for example, "ownerWallet", which should be msg.sender, is not set when the contract deploys).
            // deposits[addr] = alreadyDeposited + amt; // this line lets contract vars initialize appropriately.
        // }
        //sendFunds();
    }

    function getBalance(address _addr) constant returns (uint){
        return deposits[_addr];
    }

}

希望能帮上忙~