staticCall

1. staticcall{gas: gasAmount}(abiEncodedArguments);
2. staticcall 外部合约函数只读数据
   1. 函数必须被 view|pure 修饰，表明只读
3. 天然适用于 预编译合约
4. staticcall 无法更新状态变量:
   1. 更新合约内部的状态变量
   2. emit event 触发链上事件
   3. 创建其他合约
   4. self destruct 销毁合约（合约余额强制转移到传参地址）
   5. 转账，更新账户余额
   6. 调用其他未标记 pure/view 的函数
   7. 使用内联编码更改状态数据库

Solidity Examples

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.26;

interface IERC20 {
    function balanceOf(address) external view returns (uint256);
}

contract Token is IERC20 {
    mapping(address => uint256) balance;

    function mint(address addr, uint256 qty) external {
        balance[addr] += qty;
    }

    function balanceOf(address addr) external view returns (uint256) {
        return balance[addr];
    }
}

contract ERC20User {
    // 5837 gas cost
    function myBalance(IERC20 token, address addr)
        public
        view
        returns (uint256 balance)
    {
        balance = token.balanceOf(addr);
    }

    // 6294 gas cost
    function myBalanceLowLevelEquivalent(IERC20 token, address addr)
        public
        view
        returns (uint256 balance)
    {
        (bool ok, bytes memory result) = address(token).staticcall(
            abi.encodeWithSignature("balanceOf(address)", addr)
        );
        require(ok);

        balance = abi.decode(result, (uint256));
    }
}

Security Issues

Denial of Service

staticCall 支持指定 gas 63/64 执行只读的调用，但是对方函数逻辑不明，存在恶意消耗 gas 的安全隐患

Read only Re-entrancy

只读函数会受到其他函数的影响

Preference

https://www.rareskills.io/post/solidity-staticcall