Blur Exchange contest - neko_nyaa's results

[G-01] Using values 1 and 2 instead of false and true for boolean-like variables saves gas

2 instances

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/lib/ReentrancyGuarded.sol#L10 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L33

Setting a state variable from zero to non-zero costs a lot more gas than non-zero to non-zero. Costs more gas upon deployment, but saves significant gas for every reentrancy-guarded operations.

[G-02] Using bool instead of uint256 costs extra gas overhead

2 instances

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L71 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/lib/ReentrancyGuarded.sol#L10

[G-03] Non-state variables can be made immutable

1 instance

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L63

Since weth is an immutable, it is possible to create a constructor and initialize the variable there.

It is possible in an upgradeable context because immutables are embedded in the contract's bytecode, not its storage.

[G-04] ++i instead of i++ saves gas

5 instances

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L199 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L476 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/PolicyManager.sol#L77 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/lib/EIP712.sol#L77 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/lib/MerkleVerifier.sol#L38

[G-05] ++var instead of var += 1 saves gas

1 instance

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L208

[G-06] Caching the array length saves gas per iteration

Applies to all instances of [G-04]

It saves a small amount of gas for caching the array length, instead of reading them per loop, even when the array is memory or calldata (3 gas per loop in such case).

[G-07] Increments can be unchecked

Applies to all instances of [G-04] and [G-05]. Saves about 30-40 gas per operation.

[G-08] Fixed size bytes constants are more efficient than string constants

2 instances

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L57 https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L58

Replace string constant with bytes(1..32) constant. In general go for fixed-size data types when possible.

[G-09] require with reason strings more than 32 bytes costs more gas

2 instances

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/BlurExchange.sol#L482

Can be changed to "Total fees exceed price"

https://github.com/code-423n4/2022-10-blur/blob/main/contracts/ExecutionDelegate.sol#L22

Can be changed to "Contract is not approved"