search

code-423n4 / 2021-09-yaxis-findings

0 stars 0 forks source link

uint8 is less efficient than uint256 in loop iterations #86

Open code423n4 opened 2 years ago

code423n4 commented 2 years ago

Handle

pauliax

Vulnerability details

Impact

There are several loops that use uint8 for an index parameter (i). It does not give any efficiency, actually, it is the opposite as EVM operates on default of 256-bit values so uint8 is more expensive in this case as it needs a conversion. It only gives improvements in cases where you can pack variables together, e.g. structs.

Proof of Concept

You can try and see yourself: // SPDX-License-Identifier: MIT pragma solidity 0.6.12; contract VaultHelper { function loopUint8( uint256[] calldata _amounts ) external { uint sum = 0; for (uint8 i = 0; i < _amounts.length; i++) { // [1,2,3,4,5,6] 23892 require(_amounts[i] > 0); sum += _amounts[i]; } } function loopUint256( uint256[] calldata _amounts ) external { uint sum = 0; for (uint256 i = 0; i < _amounts.length; i++) { // [1,2,3,4,5,6] 23768 require(_amounts[i] > 0); sum += _amounts[i]; } } }

Tools Used

Remix IDE

Recommended Mitigation Steps

Replace uint8 with uint256 in loop iterations.

GalloDaSballo commented 2 years ago

Agree with finding, just KIS and use uint256