Ethereum solidity-获取具有程序集的delegatecall的返回值
我有一份合同a和一份合同B 合同A声明此功能:Ethereum solidity-获取具有程序集的delegatecall的返回值,ethereum,solidity,Ethereum,Solidity,我有一份合同a和一份合同B 合同A声明此功能: function getIntValue() constant returns (uint); 从B调用合同A的getIntValue函数时,合适的汇编代码是什么?我在装配方面还不是很有经验,所以到目前为止我只有这一点不起作用: function getContractAIntValue() constant returns (uint c) { address addr = address(contractA); // contract
function getIntValue() constant returns (uint);
从B调用合同A的getIntValue
函数时,合适的汇编代码是什么?我在装配方面还不是很有经验,所以到目前为止我只有这一点不起作用:
function getContractAIntValue() constant returns (uint c) {
address addr = address(contractA); // contract A is stored in B.
bytes4 sig = bytes4(sha3("getIntValue()")); // function signature
assembly {
let x := mload(0x40) // find empty storage location using "free memory pointer"
mstore(x,sig) // attach function signature
let status := delegatecall(sub(gas, 10000), addr, add(x, 0x04), 0, x, 0x20)
jumpi(invalidJumpLabel, iszero(status)) // error out if unsuccessful delegatecall
c := mload(x)
}
}
也许你已经解决了这个问题,因为一年多前就有人问过了,但万一有人还在找
address addr = address(contractA); // contract A is stored in B.
bytes memory sig = abi.encodeWithSignature("getIntValue()"); // function signature
// solium-disable-next-line security/no-inline-assembly
assembly {
let result := delegatecall(sub(gas, 10000), addr, add(sig, 0x20), mload(sig), 0, 0)
let size := returndatasize
let ptr := mload(0x40)
returndatacopy(ptr, 0, size)
// revert instead of invalid() bc if the underlying call failed with invalid() it already wasted gas.
// if the call returned error data, forward it
switch result case 0 { revert(ptr, size) }
default { return(ptr, size) }
}