Gas Optimizations

[code423n4]

C4-001 : Upgrade pragma to at least 0.8.4

Impact - Gas Optimization

The advantages of versions 0.8.* over <0.8.0 are:

• Safemath by default from 0.8.0 (can be more gas efficient than library based safemath.)
• Low level inliner : from 0.8.2, leads to cheaper runtime gas. Especially relevant when the contract has small functions. For example, OpenZeppelin libraries typically have a lot of small helper functions and if they are not inlined, they cost an additional 20 to 40 gas because of 2 extra jump instructions and additional stack operations needed for function calls.
• Optimizer improvements in packed structs: Before 0.8.3, storing packed structs, in some cases used an additional storage read operation. After EIP-2929, if the slot was already cold, this means unnecessary stack operations and extra deploy time costs. However, if the slot was already warm, this means additional cost of 100 gas alongside the same unnecessary stack operations and extra deploy time costs.
• Custom errors from 0.8.4, leads to cheaper deploy time cost and run time cost. Note: the run time cost is only relevant when the revert condition is met. In short, replace revert strings by custom errors.

Proof of Concept

1. The contest repository contracts contain floating pragma ^0.8.0. The contracts pragma version can be updated to 0.8.4 for the gas optimization.

• https://github.com/code-423n4/2022-01-notional/blob/main/contracts/ActionGuards.sol#L2

All Contracts

Tools Used

None

Recommended Mitigation Steps

Consider to upgrade pragma to at least 0.8.4.

C4-002 : # ++i is more gas efficient than i++ in loops forwarding

Impact

++i is more gas efficient than i++ in loops forwarding.

Proof of Concept

1. Navigate to the following contracts.

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/BribeVault.sol#L269

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/RewardDistributor.sol#L82

Tools Used

Code Review

Recommended Mitigation Steps

It is recommend to use unchecked{++i} and change i declaration to uint256.

C4-003 : # Use of constant keccak variables results in extra hashing (and so gas).

Impact

That would Increase gas costs on all privileged operations.

Proof of Concept

The following role variables are marked as constant.

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/TokemakBribe.sol#L40

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/BribeVault.sol#L27

This results in the keccak operation being performed whenever the variable is used, increasing gas costs relative to just storing the output hash. Changing to immutable will only perform hashing on contract deployment which will save gas.

See: ethereum/solidity#9232 (https://github.com/ethereum/solidity/issues/9232#issuecomment-646131646)

Tools Used

Code Review

Recommended Mitigation Steps

Consider to change the variable to be immutable rather than constant.

C4-004 : # Cache array length in for loops can save gas

Impact

Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack.

Proof of Concept

1. Navigate to the following smart contract line.

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/BribeVault.sol#L269

https://github.com/code-423n4/2022-02-redacted-cartel/blob/main/contracts/BribeVault.sol#L269

Tools Used

Code Review

Recommended Mitigation Steps

Consider caching array call data elements in the for loop.

[drahrealm]

Duplicate with previous similar gas optimization tips

[GalloDaSballo]

003 is not correct, this "myth" emerged from old contests and we busted it

[GalloDaSballo]

Very basic submission, I fell like these findings are a little too generic and compared to other warden's work there was more to be found

[GalloDaSballo]

2/10