Solidity Revert Opcode – Forward Revert Message from Low-Level Solidity Call

proxy-contractsrevert-opcodesolidity

I'm working on a proxy contract that will perform calls as follows:

bool success;
bytes memory returndata;
(success, returndata) = _to.call.value(_value)(_data);
require(success);

this works great, except that, if the call reverts with an error message, this function will simply reverts, hiding the reason string.

How can I retrieve the reason string (I assume in the returndata) and use if to revert properly

Best Answer

It is simpler than you think:

require(success, string (returndata));

See documentation for details. You may also forward raw bytes, but you will need to use assembly.

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Solidity – Handling Unimplemented Functions in Contracts

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

Using Low Level Call Function on EOA in Solidity

(moving my comment to an answer as requested)

Yes, this call should succeed. In general, a call will succeed unless the receiving address reverts. The difference between an EOA and a contract is that the contract has code (and so that code might revert, e.g. if it doesn't have a given function defined and lacks a fallback function). An EOA doesn't have code, so it can't possibly revert.

Best Answer

Related Solutions

Solidity – Handling Unimplemented Functions in Contracts

Using Low Level Call Function on EOA in Solidity

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