Less than 256 uints are not gas efficient

[code423n4]

Handle

defsec

Vulnerability details

Impact

Lower than uint256 size storage instance variables are actually less gas efficient. E.g. using uint16 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

1. Navigate to the following contracts.

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/singleJoinExit/SingleNativeTokenExit.sol#L26

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/singleJoinExit/SingleTokenJoinV2.sol#L37

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/singleJoinExit/SingleNativeTokenExitV2.sol#L36

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/singleJoinExit/SingleTokenJoin.sol#L27

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/facets/Basket/BasketFacet.sol#L143

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/facets/Basket/BasketFacet.sol#L188

https://github.com/code-423n4/2021-12-amun/blob/cf890dedf2e43ec787e8e5df65726316fda134a1/contracts/basket/contracts/facets/ERC20/ERC20Facet.sol#L63

Tools Used

None

Recommended Mitigation Steps

Consider to review all uint types. Change them with uint256 If the integer is not necessary to present with 16.