使用代码块解决 Error:stack too deep

title: 使用代码块解决 Error:stack too deep date: 2024-6-24 16:58 tags: null

使用代码块解决stack too deep

你是否也有过这样的报错信息：“stack too deep”

这是因为solidity一个函数中可容纳的变量的数量最大为16个，超过这个数量就会报错 那如果想在函数中声明更多的变量该怎么办呢？

可以使用代码块 如下所示:

// SPDX-License-Identifier: MIT
pragma solidity 0.8.20;
import "hardhat/console.sol";

contract C {
    function minimalScoping()  public returns (string memory){
        string memory para0="0xaaaa";
        string memory para1="";
        string memory para2="";
        string memory para3="";
        string memory para4="";
        string memory para5="";
        string memory para6="";
        string memory para7="";
        string memory para8="";
        string memory para9="";

        {  //A
        string memory para10="";
        string memory para11="";
        string memory para12="";
        string memory para15="";
        string memory para17="lllll";
        }

        {  //B
        string memory para18="lllll";
        string memory para19="lllll";
        string memory para20="lllll";
        string memory para21="lllll";
        string memory para22="lllll";

        }
return para0;

    }

}

在代码块A中，无法检测到B中的变量，同理，B中无法检测到A中的变量，因此，只要将部分变量写入代码块中，就可以做到在同一函数中声明大量变量

uniswap V2的UniswapV2Pair.sol的swap函数便使用了这个机制

  function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external lock {
        require(amount0Out > 0 || amount1Out > 0, 'UniswapV2: INSUFFICIENT_OUTPUT_AMOUNT');
        (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
        require(amount0Out < _reserve0 && amount1Out < _reserve1, 'UniswapV2: INSUFFICIENT_LIQUIDITY');

        uint balance0;
        uint balance1;
        { // scope for _token{0,1}, avoids stack too deep errors
        address _token0 = token0;
        address _token1 = token1;
        require(to != _token0 && to != _token1, 'UniswapV2: INVALID_TO');
        if (amount0Out > 0) _safeTransfer(_token0, to, amount0Out); // optimistically transfer tokens
        if (amount1Out > 0) _safeTransfer(_token1, to, amount1Out); // optimistically transfer tokens
        if (data.length > 0) IUniswapV2Callee(to).uniswapV2Call(msg.sender, amount0Out, amount1Out, data);
        balance0 = IERC20(_token0).balanceOf(address(this));
        balance1 = IERC20(_token1).balanceOf(address(this));
        }
        uint amount0In = balance0 > _reserve0 - amount0Out ? balance0 - (_reserve0 - amount0Out) : 0;
        uint amount1In = balance1 > _reserve1 - amount1Out ? balance1 - (_reserve1 - amount1Out) : 0;
        require(amount0In > 0 || amount1In > 0, 'UniswapV2: INSUFFICIENT_INPUT_AMOUNT');
        { // scope for reserve{0,1}Adjusted, avoids stack too deep errors
        uint balance0Adjusted = balance0.mul(1000).sub(amount0In.mul(3));
        uint balance1Adjusted = balance1.mul(1000).sub(amount1In.mul(3));
        require(balance0Adjusted.mul(balance1Adjusted) >= uint(_reserve0).mul(_reserve1).mul(1000**2), 'UniswapV2: K');
        }