Solidity – How to Alter the Gas Stipend with High-Level Delegate Call

delegatecallgassolidity

When using the DELEGATECALL opcode via assembly, we can pass a specific amount of gas:

let result := delegatecall(gas(), implementation, 0, calldatasize(), 0, 0)

But the high-level DELEGATECALL does not have such argument:

(bool success, bytes memory returndata) = target.delegatecall(data);

How can we alter the gas stipend that we give to the delegated contract?

Best Answer

You can specify the gas using the gas modifier (in brackets) before the function args, e.g.:

(bool success, bytes memory returndata) = target.delegatecall{ gas: 10000 }(data);

The modifiers are documented here:

https://docs.soliditylang.org/en/v0.8.16/types.html#address

Related Solutions

[Ethereum] How to use delegatecall assembly with a storage pointer to a struct

From what I can gather mstore() will write in 32 byte chunks, therefore mstore(in_pos, 0x04) is still in the same space as in_pos and will overwrite the 4 bytes function signature.

What I ended up doing is writing the 4 bytes in the first 32 bytes, the 1st arg in the 2nd 32 bytes and the 2nd arg in the 3rd 32 bytes, then called delegatecall pointing to the start of the 4 byte signature by using a 28 byte offset.

delegatecall(sub(gas, 1000), t, add(in_pos, 28), 0x44, in_pos, 0x20)

[Ethereum] Using a high level delegate call in upgradable contracts since Byzantium

One issue is that you copy your data into memory starting at address 0. This will work for return sizes less than 64 bytes, but will start overwriting other memory at that point.

Instead you should do something more like

let m := mload(0x40)
returndatacopy(m, 0, returndatasize)
return(0, returndatasize)

Best Answer

Related Solutions

[Ethereum] How to use delegatecall assembly with a storage pointer to a struct

[Ethereum] Using a high level delegate call in upgradable contracts since Byzantium

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