Gas Optimizations

[code423n4]

Impact

[1] Consider using optimized for-loop and apply the following optimizations:

1. cache .length into local variable to avoid looking up every for-loop iteration.
2. using ++i consumes 5 less gas than i++ (same applies to --i)
3. using unchecked keyword for counter i unchecked{ ++i; } consumes 49 less gas each iteration (same applies to --i)
4. don't initialize uint256 i = 0; instead use the default value uint256 i;
5. make sure to specify uint256 type instead of uint type for readability

Affected code:

1. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L106
2. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L218
3. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L120
4. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L130
5. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L156

Proof of Concept

Tools Used

Recommended Mitigation Steps

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Impact

[2] Using x != 0 uses 6 less gas than x > 0.
Consider changing all "greater than zero" comparisons to "not equal to zero".

Affected code:

1. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L75
2. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L36
3. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L131

Proof of Concept

Tools Used

Recommended Mitigation Steps

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Impact

[3] You can upgrade to modern 0.8.4+ solidity version in order to save gas.
Custom errors are reducing 38 gas if condition is met and 22 gas otherwise.
Also reduces contract size and deployment costs.

Affected code:

1. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/CollateralAdapter.sol#L18
2. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L38
3. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L71
4. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L95
5. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L101
6. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L137
7. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L183
8. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L184
9. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/ConvexCurveLPVault.sol#L197
10. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L30
11. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L35
12. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L125
13. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L166
14. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L167
15. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/GeneralVault.sol#L179
16. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L88
17. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L92
18. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L97
19. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L142
20. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/LidoVault.sol#L145
21. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L52
22. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L65
23. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L97
24. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L122
25. https://github.com/code-423n4/2022-05-sturdy/blob/main/smart-contracts/YieldManager.sol#L203

Proof of Concept

Tools Used

Recommended Mitigation Steps

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Impact

[4] Consider using if (stAssetBalance > aTokenBalance) return stAssetBalance.sub(aTokenBalance); because in if these values are equal return value will be zero.
This will save some gas.

Affected code:

1. https://github.com/code-423n4/2022-05-sturdy/blob/78f51a7a74ebe8adfd055bdbaedfddc05632566f/smart-contracts/GeneralVault.sol#L196

Proof of Concept

Tools Used

Recommended Mitigation Steps

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