Solidity – How to Use Delegatecall to an Internal Function

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Let's say I have a Dispatcher contract that delegates all function calls to an Implementation contract using delegatecall (see for example https://gist.github.com/Arachnid/4ca9da48d51e23e5cfe0f0e14dd6318f).

To initialise the Dispatcher with some value uint value1 I want to (delegate)call, from the constructor of Dispatcher, an init() method of the Implementation and pass it value1. For security reasons I would like to mark the init() method of Implementation as internal… but it does not seem to work.

I know I can make the init() method of Implementation public with some custom modifier but I would like to understand why the delegatecall to the internal method is not working.

Best Answer

if you are trying to call the init() method in Implementation from Dispatcher using delegatecall , internal will not work. As the internal function visibility specifier only refers to that function being called from inside the contract. So if the delegatecall is in the constructor of the contract, then you will not need to specify anything as the constructor is only run once and that is when the contract is deployed. You cannot call the constructor after it has been deployed.

Related Solutions

Solidity Delegatecall – Understanding Function Return Values

delegatecall is not supposed to handle return values as it cannot be aware of the length of the other side (unless there would be a dedicated parameter passed to it). Currently, the delegatecall Solidity built-in method does not support supplying the return value size, nor getting the return value out after the call.

According to the documentation it should always return a boolean signaling the execution outcome. It seems the compiler may currently have a problem, see https://github.com/ethereum/solidity/issues/2678.

To get the result out, you will need to know the return value size and use inline assembly:

assembly {
    let returnSize = 32
    calldatacopy(0xff, 0, calldatasize)
    let _retVal = delegatecall(gas, currentVersion, 0xff, calldatasize, 0, returnSize)
    switch _retval case 0 { revert(0,0) } default { return(0, returnSize) }
}

Solidity – Can Internal Functions Be Called Using delegatecall?

No, it is not possible because internal function do not have an entry point in the contract function dispatcher. The whole point of internal function is that they are not callable from outside the contract.

You can call a public function and make that function call the internal function.

Best Answer

Related Solutions

Solidity Delegatecall – Understanding Function Return Values

Solidity – Can Internal Functions Be Called Using delegatecall?

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