delegatecall example

src/examples/DelegateCall.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.13;
+
+contract B {
+    uint256 public num;
+    address public sender;
+    uint256 public value;
+
+    function setVars(uint256 _num) public payable {
+        num = _num;
+        sender = msg.sender;
+        value = msg.value;
+    }
+
+    function collate_propagate_storage(bytes16 data) public payable {
+        num = 1e5;
+    }
+}
+
+contract A {
+    uint256 public num;
+    address public sender;
+    uint256 public value;
+
+    function setVarsDelegateCall(address _contract, uint256 _num) public payable {
+        (bool success, bytes memory data) = _contract.delegatecall(abi.encodeWithSignature("setVars(uint256)", _num));
+    }
+
+    function setVarsCall(address _contract, uint256 _num) public payable {
+        (bool success, bytes memory data) = _contract.call(abi.encodeWithSignature("setVars(uint256)", _num));
+    }
+
+    function delegeCallBurn(address _contract, uint256 _num) public payable {
+        bytes16 h = 0x20010db8000000000000000000000001;
+        (bool success, bytes memory data) = _contract.delegatecall(abi.encodeWithSignature("burn(uint256)", h));
+    }
+}
+
+contract C {
+    uint256 public value;
+    uint256 public num;
+
+    address public sender;
+
+    function setVarsDelegateCall(address _contract, uint256 _num) public payable {
+        (bool success, bytes memory data) = _contract.delegatecall(abi.encodeWithSignature("setVars(uint256)", _num));
+    }
+
+    function setVarsCall(address _contract, uint256 _num) public payable {
+        (bool success, bytes memory data) = _contract.call(abi.encodeWithSignature("setVars(uint256)", _num));
+    }
+}

test/examples/DelegateCall.t.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.13;
+
+import { Test, console2 } from "forge-std/src/Test.sol";
+import { A, B, C } from "../../src/examples/DelegateCall.sol";
+
+contract DelegateCallTest is Test {
+    A a;
+    B b;
+    C c;
+    address alice = makeAddr("alice");
+
+    function setUp() public {
+        a = new A();
+        b = new B();
+        c = new C();
+    }
+
+    function testCall() public {
+        vm.startPrank(alice);
+        vm.deal(alice, 1 ether);
+        a.setVarsCall{ value: 1 ether }(address(b), 11); // call setVars by call
+        assertEq(b.num(), 11);
+        assertEq(b.sender() == address(a), true); // the msg.sender in contract b is a, is not alice
+        assertEq(b.value(), 0); // contract b will not receive any ether
+
+        vm.stopPrank();
+    }
+
+    function testDelegateCall() public {
+        vm.startPrank(alice);
+        vm.deal(alice, 1 ether);
+        a.setVarsDelegateCall{ value: 1 ether }(address(b), 11); // call setVars by call
+        console2.log("value from contact b ----------");
+        console2.log(b.num());
+        console2.log(b.sender());
+        console2.log(b.value());
+        console2.log("------------");
+        // all the value in the contact b will not change
+        // 实际上仅仅改变的是contract a中的值，相当于是把合约b中的function提到a中来执行,
+        // 所以就需要两个合约中的存储结构是一致的。因为合约a执行合约b中的方法的时候对变量进行修改是按照变量在b中的槽位来进行修改
+
+        assertEq(a.num(), 11);
+        assertEq(a.sender(), alice); // the msg.sender in contract b is a, is not alice
+        assertEq(a.value(), 1 ether); // contract b will not receive any ether
+        vm.stopPrank();
+    }
+
+    function testDelegateCallNameConfict() public {
+        vm.startPrank(alice);
+        vm.deal(alice, 1 ether);
+        a.delegeCallBurn{ value: 1 ether }(address(b), 11); // call setVars by call
+        console2.log("value from contact b ----------");
+        console2.log(b.num());
+        console2.log(b.sender());
+        console2.log(b.value());
+        console2.log("------------");
+        // all the value in the contact b will not change
+        // 实际上仅仅改变的是contract a中的值，相当于是把合约b中的function提到a中来执行,
+        // 所以就需要两个合约中的存储结构是一致的。因为合约a执行合约b中的方法的时候对变量进行修改是按照变量在b中的槽位来进行修改
+
+        // 可以通过合约代码看到，用户可能以为调用的是burn方法，其实通过代理调用的并不是burn方法，而是collate_propagate_storage(bytes16)
+        // 这是因为函数签名发生了冲突，函数签名是取该函数hash的前4位，而delegatecall是通过函数签名的方式去对应合约地址中寻找函数，导致找到的函数有可能不是我们想要的
+        console2.log("value from contact b ----------");
+        console2.log(a.num());
+        console2.log(a.sender());
+        console2.log(a.value());
+        console2.log("------------");
+
+        vm.stopPrank();
+    }
+
+    function testCDelegateCall() public {
+        vm.startPrank(alice);
+        vm.deal(alice, 1 ether);
+        c.setVarsDelegateCall{ value: 1 ether }(address(b), 11); // call setVars by call
+        console2.log("value from contact b ----------");
+        console2.log(b.num());
+        console2.log(b.sender());
+        console2.log(b.value());
+        console2.log("------------");
+        // all the value in the contact b will not change
+        // 实际上仅仅改变的是contract a中的值，相当于是把合约b中的function提到a中来执行,
+        // 所以就需要两个合约中的存储结构是一致的。因为合约a执行合约b中的方法的时候对变量进行修改是按照变量在b中的槽位来进行修改
+        // 当合约C的布局和合约b的布局不一致的时候，就会出现问题，因为合约C中的变量在b中的槽位不一致
+        // delegatecall执行的方法会按照合约b中的槽位给c中的变量进行复制
+        console2.log("value from contact c ----------");
+        console2.log(c.num());
+        console2.log(c.sender());
+        console2.log(c.value());
+        console2.log("------------");
+        vm.stopPrank();
+    }
+}