Gas Optimizations #204

code423n4 · 2022-05-24T01:31:59Z

Redundant initialisation with default value

Some variables are initialised with their default values which cause unnecessary gas consumption

Lines of code

Some public constants and immutables can be made private

There are many public constants and immutables which can be converted to private. Some of them are below.

Lines of code

https://github.com/code-423n4/2022-05-aura/blob/main/contracts/Aura.sol#L26-L30
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L29
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L73
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L81
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L83
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L107

for loops can be optimized

1- For loop index increments can be made unchecked for solidity versions > 0.8.0. There is no risk of overflowing the index of the for loops. Therefore, they can be changed to unchecked to save gas. This would save more gas as iterations in the loop increases.
2- Postfix increments can be changed as prefix as it is cheaper.
3- There is no need to set uint256 variable to 0 since default value is already 0.

Lines of code

Recommended Mitigation Steps

I suggest to change the original code from this
for (uint256 i = 0; i < rewardContracts.length; i++) {
IBasicRewards(rewardContracts[i]).getReward(msg.sender, true);
}
to this
for (uint256 i; i < rewardContracts.length; ) {
IBasicRewards(rewardContracts[i]).getReward(msg.sender, true);
unchecked { ++i; }
}

Using != 0 is cheaper than > 0 when used on a uint in a require() statement

Lines of code

There are many instances, some of which are listed below:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/Aura.sol#L68
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L121
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L139
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L157
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L210

Error string longer than 32 characters

Error strings take space in the deployed bytecode. Every reason string takes at least 32 bytes so make sure your string fits in 32 bytes or it will become more expensive.

Lines of code

https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L197

Missing non-zero amount checks

It is a good practice to apply non-zero amount checks for token transactions to avoid unnecessary executions. This has been applied in most of the transactions, but still there are some missing instances.

Lines of code

https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L198
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L251
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraMerkleDrop.sol#L100
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraStakingProxy.sol#L162
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraVestedEscrow.sol#L123
https://github.com/code-423n4/2022-05-aura/blob/main/convex-platform/contracts/contracts/BaseRewardPool.sol#L179
https://github.com/code-423n4/2022-05-aura/blob/main/convex-platform/contracts/contracts/BaseRewardPool.sol#L198

It is better to use 1-2 for binary variables rather than 0-1

SSTORE from 1 to 2 is cheaper than SSTORE from 0 to 1. Therefore, some booleans such as isShutdown, isForceTimerStarted, isSealed, etc can be defined as uint and their values can be switched between 1-2.
code-423n4/2022-01-yield-findings#102

Lines of code

https://github.com/code-423n4/2022-05-aura/blob/main/convex-platform/contracts/contracts/Booster.sol#L54
https://github.com/code-423n4/2022-05-aura/blob/main/convex-platform/contracts/contracts/BoosterOwner.sol#L49
https://github.com/code-423n4/2022-05-aura/blob/main/convex-platform/contracts/contracts/BoosterOwner.sol#L53

Booleans are more expensive than uint256

It is more expensive to operate using booleans because before every write operation an SLOAD is executed to read the contents of the slot. Therefore, it is cheaper to use uint256 instead of bool. On the other hand, using bool is better for the code readability. Hence, it is a tradeoff to be decided by the developers.

code423n4 added bug Something isn't working G (Gas Optimization) labels May 24, 2022

code423n4 added a commit that referenced this issue May 24, 2022

catchup issue #204

cbf6f81

0xMaharishi added the duplicate This issue or pull request already exists label May 27, 2022

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Gas Optimizations #204

Gas Optimizations #204

code423n4 commented May 24, 2022

Gas Optimizations #204

Gas Optimizations #204

Comments

code423n4 commented May 24, 2022

Redundant initialisation with default value

Lines of code

Some public constants and immutables can be made private

Lines of code

for loops can be optimized

Lines of code

Recommended Mitigation Steps

Using != 0 is cheaper than > 0 when used on a uint in a require() statement

Lines of code

Error string longer than 32 characters

Lines of code

Missing non-zero amount checks

Lines of code

It is better to use 1-2 for binary variables rather than 0-1

Lines of code

Booleans are more expensive than uint256