How do I decode the bytes from an address call return?

Question

I'm using the following to send eth to a contract using solidity 0.8.16:

(bool success, bytes memory data) = payable(msg.sender).call{value:someEth}("");

I've tried to get the info from the data variable, but without success.

Attempt 1: string memory b = string(data);

This returns an error with the following:

HardhatChaiMatchersDecodingError: There was an error decoding
'0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000006408c379a00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000001f5265656e7472616e637947756172643a207265656e7472616e742063616c6c0000000000000000000000000000000000000000000000000000000000' as a string

If I decode the section with values, it's trying to describe the nonReentrant error. If I decode the whole thing, it flags an issue with the continuation byte.

Attempt 2: (string memory a) = abi.decode(data, (string));

This runs into a runtime error my ide (hardhat) can't parse:

Transaction reverted and Hardhat couldn't infer the reason.

How do I properly decode the data from this return?

Answer 1

You can take a look at this resource on how to decode return bytes from address.call. It hinges on using abi.encodeWithSignature('ADDRESS_OF_CONTRACT'):

Decoding return bytes from Solidity `address.call`

Answer 2

So the bytes being returned by the call to an address will end up hitting the fallback function (because it's not targeting any particular function).

I added this package in order to slice the byte array.
I skipped the first 68 bytes (4 bytes for the selector, 64 bytes for something else) and grabbed the rest of the array, casting it to a string using the openzeppelin Strings.sol extensions. It ends up being something like:

function parseError (bytes memory val) private pure returns (string memory)
{
    require(val.length>68, Strings.toString(val.length));
    return string(BytesLib.slice(val, 68,val.length-68));
}

I still don't know what the extra 64 bits is for, but might be from the calldata being passed to the fallback.