solidity的call跟delegatecall

call
原型
<address>.call(...) returns (bool)
简介
调用后内置变量 msg .sender的值会修改为调用者合约地址，涉及存储修改，修改的是被调用者合约的内存（<address>的）。默认情况下将所有可用的gas传输过去，gas传输量可调。执行失败时返回false。
如果调用的函数不存在，则调用fallback函数；

实例
//call的函数调用
nameReg.call("register", "MyName");
nameReg.call(bytes4(keccak256("fun(uint256)")), a);
//设置调用时的gas和传输的钱
nameReg.call.gas(1000000).value(1 ether)("register", "MyName");

delegatecall
原型
<address>.delegatecall(...) returns (bool)

简介
调用后内置变量 msg .sender的值不会修改为调用者合约地址，涉及存储修改，修改的是调用者合约的内存（当前合约的），默认情况下将所有可用的gas传输过去，gas传输量可调。执行失败时返回false。
本函数目的在于让合约能够在不传输自身状态(如balance、storage)的情况下使用其他合约的代码。

实例
nameReg.delagatecall.gas(1000000)("register", "MyName");
//delegatecall不支持.value

call与delegatecall对比简析
相同之处
（1）调用时会将本合约所有可用的gas传输过去
（2）执行失败均返回false

不同之处
（1）call可以使用.value传ETH给被调用合约
（2）假设在contract_test合约中分别有nameReg.call("somefunction")以及nameReg.delegatecall("somefunction")
nameReg.call以nameReg合约的身份在nameReg中执行somefunction
nameReg.delegatecall以contract_test合约的身份在nameReg中执行somefunction
（3）delegatecall的目的就是让合约在不用传输自身状态(如balance、storage)的情况下可以使用其他合约的代码

测试如下：

pragma solidity ^0.4.0;

contract Proxy {
/**
* @dev Tells the address of the implementation where every call will be delegated.
* @return address of the implementation to which it will be delegated
*/
function implementation() public view returns (address);

/**
* @dev Fallback function allowing to perform a delegatecall to the given implementation.
* This function will return whatever the implementation call returns
*/
function () payable public {
address _impl = implementation();
require(_impl != address(0));

assembly {
let ptr := mload(0x40)
calldatacopy(ptr, 0, calldatasize)
let result := delegatecall(gas, _impl, ptr, calldatasize, 0, 0)
let size := returndatasize
returndatacopy(ptr, 0, size)

switch result
case 0 { revert(ptr, size) }
default { return(ptr, size) }
}
}
}

library SomeLib {
event CalledSomeLib(address _from);
function calledSomeLibFun() public {
emit CalledSomeLib(this);
}
}

contract TestContract {
uint num = 10;
event callMeMaybeEvent(address sender, address _from);
function callMeMaybe() payable public {
num = num + 1;
emit callMeMaybeEvent(msg.sender,this);
}
function getNum() public view returns(uint256){
return num;
}
}

contract CallsTestContract is Proxy {
uint num;
address smart;

function set(address _addr) public {
smart = _addr;
}

function implementation() public view returns (address){
return smart;
}

function callTheOtherContract(address _contractAddress) public {
require(_contractAddress.call(bytes4(keccak256("callMeMaybe()"))));
require(_contractAddress.delegatecall(bytes4(keccak256("callMeMaybe()"))));
require(address(this).call(bytes4(keccak256("callMeMaybe()"))));
require(address(this).delegatecall(bytes4(keccak256("callMeMaybe()"))));
SomeLib.calledSomeLibFun();
}

function getNum() public view returns(uint256){
return num;
}
}

部署合约（账户地址：0xca35b7d915458ef540ade6068dfe2f44e8fa733c）
1、先部署TestContract; （合约地址：0xcbbe6ec46746218a5bed5b336ab86a0a22804d39）
2、再部署CallsTestContract；（合约地址：0x100eee74459cb95583212869f9c0304e7ce11eaa）
3、以TestContract合约地址为参数，调用CallsTestContract的set方法；
4、以TestContract合约地址为参数，调用CallsTestContract的callTheOtherContract方法；

生成logs如下：

[
   {
       "from": "0xcbbe6ec46746218a5bed5b336ab86a0a22804d39",
       "topic": "0x6f047d87ead77bed598fcd7848a13aaf5af905a842213507a0ebc158d568351b",
       "event": "callMeMaybeEvent",
       "args": {
           "0": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "1": "0xCBbe6ec46746218A5beD5b336AB86a0A22804d39",
           "sender": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "_from": "0xCBbe6ec46746218A5beD5b336AB86a0A22804d39",
           "length": 2
       }
   },
   {
       "from": "0x100eee74459cb95583212869f9c0304e7ce11eaa",
       "topic": "0x6f047d87ead77bed598fcd7848a13aaf5af905a842213507a0ebc158d568351b",
       "event": "callMeMaybeEvent",
       "args": {
           "0": "0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c",
           "1": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "sender": "0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c",
           "_from": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "length": 2
       }
   },
   {
       "from": "0x100eee74459cb95583212869f9c0304e7ce11eaa",
       "topic": "0x6f047d87ead77bed598fcd7848a13aaf5af905a842213507a0ebc158d568351b",
       "event": "callMeMaybeEvent",
       "args": {
           "0": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "1": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "sender": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "_from": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "length": 2
       }
   },
   {
       "from": "0x100eee74459cb95583212869f9c0304e7ce11eaa",
       "topic": "0x6f047d87ead77bed598fcd7848a13aaf5af905a842213507a0ebc158d568351b",
       "event": "callMeMaybeEvent",
       "args": {
           "0": "0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c",
           "1": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "sender": "0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c",
           "_from": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "length": 2
       }
   },
   {
       "from": "0x100eee74459cb95583212869f9c0304e7ce11eaa",
       "topic": "0x5e7091f10fdcc639a86214a4a72e1b3d6e058d14be100fbe52d22ca354ef18ec",
       "event": "CalledSomeLib",
       "args": {
           "0": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "_from": "0x100eeE74459CB95583212869f9c0304e7cE11EAA",
           "length": 1
       }
   }
]

分析logs得到的msg.sender顺序为：
   0x100eee74459cb95583212869f9c0304e7ce11eaa ---> CallsTestContract（当前合约地址）
   0xca35b7d915458ef540ade6068dfe2f44e8fa733c ---> 执行函数的账户地址
   0x100eee74459cb95583212869f9c0304e7ce11eaa ---> CallsTestContract（当前合约地址）
   0xca35b7d915458ef540ade6068dfe2f44e8fa733c ---> 执行函数的账户地址

CallsTestContract的callTheOtherContract方法里有四种调用：(logs的_from字段)
   第一种是以TestContract身份去调用TestContract的代码，如果涉及修改内存，修改的是TestContract的内存；
   第三种是以CallsTestContract身份去调用TestContract的代码；如果涉及修改内存，修改的是CallsTestContract的内存；
   第二、四个也是以CallsTestContract身份去调用TestContract的代码，如果涉及修改内存，修改的是CallsTestContract的内存；

所以，运行结束后，TestContract的num值为11（仅修改一次）， CallsTestContract的值为13（修改三次）；

callcode: 调用后内置变量 `msg.sender` 的值会修改为调用者合约地址，涉及存储修改，修改的是调用者合约的内存（当前合约的）。

参考：
https://www.jianshu.com/p/fd5075ff0ab9
https://zhuanlan.zhihu.com/p/35292014

https://www.anquanke.com/post/id/145458
https://paper.seebug.org/633/