Should be able to specify safeTxGas on factory

[rmeissner]

To ensure that enough gas is available for executing the Safe transaction on deployment (which is required so that other wallets can properly estimate the required gas) it should be possible to specify the safeTxGas for the Safe transaction performed on deployment

see https://github.com/gnosis/contract-proxy-kit/blob/master/contracts/CPKFactory.sol#L41

Currently if you try to perform a transaction with a gas costs together with deployment, metamask will fail to properly estimate that.

Work around for now could be that we to binary search on the returned success value and set this as the proposed gas value on the tx send to the connected wallet.

[rmeissner]

Geth support code injection for addresses. So we can create the runtime code for a simple estimation contract:

contract Snipped {
    enum Operation {
        Call,
        DelegateCall
    }

    function execute(address to, uint256 value, bytes memory data, Operation operation, uint256 txGas)
        internal
        returns (bool success)
    {
        if (operation == Operation.Call)
            success = executeCall(to, value, data, txGas);
        else if (operation == Operation.DelegateCall)
            success = executeDelegateCall(to, data, txGas);
        else
            success = false;
    }

    function executeCall(address to, uint256 value, bytes memory data, uint256 txGas)
        internal
        returns (bool success)
    {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := call(txGas, to, value, add(data, 0x20), mload(data), 0, 0)
        }
    }

    function executeDelegateCall(address to, bytes memory data, uint256 txGas)
        internal
        returns (bool success)
    {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := delegatecall(txGas, to, add(data, 0x20), mload(data), 0, 0)
        }
    }

     function requiredTxGas(address to, uint256 value, bytes calldata data, Operation operation)
        external
        returns (uint256)
    {
        uint256 startGas = gasleft();
        // We don't provide an error message here, as we use it to return the estimate
        // solium-disable-next-line error-reason
        require(execute(to, value, data, operation, gasleft()));
        uint256 requiredGas = startGas - gasleft();
        // Convert response to string and return via error message
        return requiredGas;
    }
}

and then call it with an rpc call

{
        "jsonrpc": "2.0",
        "method": "eth_call",
        "params": [
            {
                "to": "0x9913B9180C20C6b0F21B6480c84422F6ebc4B808",
                "data": "0xc4ca3a9c00000000000000000000000005c85ab5b09eb8a55020d72daf6091e04e264af9000000000000000000000000000000000000000000000000000009184e72a000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
            },
            "latest",
            {
                "0x9913B9180C20C6b0F21B6480c84422F6ebc4B808": {
                    "code": "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"
                }
            }
        ],
        "id": 1
}

this way we get back the estimated gas

{
        "jsonrpc": "2.0",
        "id": 1,
        "result": "0x0000000000000000000000000000000000000000000000000000000000001ea5"
}

The really nice part about this is, that this will also work even if the Safe is not deployed yet, so we could estimate the gas for the transaction nested into the deployment in the CPKFactory

Edit: contract could be simplified, but I wanted to have the same interface as the Safe contract ;)