New type of call - DELEGATESTATICCALL

EIPs
1

The idea is pretty simple, introduce a DELEGATECALL like functionality that restricts state mutations on EVM level just like a STATICCALL does. The idea seems simple and surprised it doesn’t already exist. So I am wondering if there’s any reason this hasn’t already been done? I am no EL dev, but I think the work should be very similar to all other type of calls and could use a lot of reuse(DELEGATECALL + STATICCALL).

This also opens up a very simple way to allow users to write custom views on a foreign contract if the said contract chooses to expose a function that does arbitrary delegatestaticcalls. Would also allow contracts to only keep the core state mutating + necessary view functions and in turn give more room for more code given the code size limits. Could also serve as a poor man’s opt-in workaround for EXTSLOADs too.

contract SomeContract {
  function extview(address _impl, bytes calldata _data) external view returns (bool _success, bytes memory _ret) {
    (_success, _ret) = _impl.delegatestaticcall(_data);
  }
}
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2

It’s possible (but a bit of a hack) to do something like this by 1) making a normal delegatecall 2) reverting with its return data, and 3) catching the revert and decoding the result of the original call from the error. Here’s one example of the pattern I know of in the wild.

Would definitely be less expensive with its own opcode!

3

Yes, thats the way to do it right now for sure. But evm level restrictions on mutations would be nice just the same as staticcall. Technically could implement a static call in a similar fashion too.

Revert method requires you to have a new CALL since you want to revert it. Couldn’t be like a internal call jump to a _delegatestaticcall since it will revert the complete existing call. It’d have to be like address(this).call(...) and require more gas as you said and everyone to implement it in their contracts.

1 Like