Gas Optimizations #2

code423n4 · 2022-08-01T20:56:18Z

1. Use of custom error and revert() instead of require()

Starting from Solidity v0.8.4, there is a convenient and gas-efficient way to explain to users why an operation failed through the use of custom errors. Until now, you could already use strings to give more information about failures (e.g., revert("Insufficient funds.");), but they are rather expensive, especially when it comes to deploy cost, and it is difficult to use dynamic information in them.

In the below code references, require can be replaced with if (a != b) revert ERROR()

2. Use of != 0 instead of > 0 for integer comparison

Use of != 0 instead of > 0 is more cheaper.
Below code references can be updated to use !=0

Code:
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Community.sol#L261
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Community.sol#L427
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Community.sol#L840
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/HomeFi.sol#L245
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L380
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L691

3. Use of unchecked block in loops

Although solidity 0.8.0 onwards, all arithmetic operations rever on over and underflow by defaults, it's best to use an unchecked block for any arithmetic operations to save gas fees

Code references where this can be safely implemented,
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Community.sol#L140
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/HomFi.sol#L289
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L179
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L250
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L290
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L625
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L672

4. Use of bytes32 than string

A string is a dynamic data structure and therefore is more gas-consuming than bytes32.
For below code references, including function parameters, bytes32 can be used instead of string

Code:
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/DebtToken.sol#L45-46
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/HomeFi.sol#L284

5. Use external vs public if not called within

For all the public functions, the input parameters are copied to memory automatically, and it costs gas. If your function is only called externally, then you should explicitly mark it as external. External function parameters are not copied into memory but are read from calldata directly. This small optimization in your solidity code can save you a lot of gas when the function input parameters are huge.

For below code references, function visibility can be changed to external
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/DebtToken.sol#L91

6. mintNFT return value is not used

function mintNFT returns a value that is never used. No need to return value, this can save some gas.

Code:
https://github.com/code-423n4/2022-08-rigor/blob/main/contracts/HomeFi.sol#L284

7. Rearrange code to save some extra gas

Code;
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Community.sol#L235

L228 // Local instance of community and community project details. For saving gas.
L229 CommunityStruct storage _community = _communities[_communityID];
L230 ProjectDetails storage _communityProject = _community.projectDetails[_project];
L235 require(_publishNonce == _community.publishNonce,"Community::invalid publishNonce");

The above require statement at line 235 can be moved after line 229. If the decoded nonce is incorrect, no need to create _communityProject storage variable at line 230.
The above block can be rearranged to save some gas by not creating an extra storage variable as below.

L228 // Local instance of community and community project details. For saving gas.
L229 CommunityStruct storage _community = _communities[_communityID];
L235 require(_publishNonce == _community.publishNonce,"Community::invalid publishNonce");
L230 ProjectDetails storage _communityProject = _community.projectDetails[_project];

Similarly, line 241 can be moved to line 227.

Reverts if _project not originated from HomeFi
require(homeFi.isProjectExist(_project), "Community::Project !Exists");

8 Duplicate variable casting is not needed

Code:
https://github.com/code-423n4/2022-08-rigor/tree/main/contracts/Project.sol#L198-200

In the above function, variable _newTotalLEnt is being type casted again at line 200. This is not necessary and can consume more gas.
Remove the double casting.

zgorizzo69 · 2022-08-07T12:12:48Z

We need the actual name and symbol for the token

zgorizzo69 · 2022-08-07T12:20:11Z

Good job 👍

code423n4 added bug Something isn't working G (Gas Optimization) labels Aug 1, 2022

code423n4 added a commit that referenced this issue Aug 1, 2022

samruna issue #2

1145eac

code423n4 added the edited-by-warden label Aug 1, 2022

This was referenced Aug 4, 2022

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Gas Optimizations #2

Gas Optimizations #2

code423n4 commented Aug 1, 2022 •

edited

zgorizzo69 commented Aug 7, 2022

zgorizzo69 commented Aug 7, 2022

Gas Optimizations #2

Gas Optimizations #2

Comments

code423n4 commented Aug 1, 2022 • edited

1. Use of custom error and revert() instead of require()

2. Use of != 0 instead of > 0 for integer comparison

3. Use of unchecked block in loops

4. Use of bytes32 than string

5. Use external vs public if not called within

6. mintNFT return value is not used

7. Rearrange code to save some extra gas

8 Duplicate variable casting is not needed

zgorizzo69 commented Aug 7, 2022

zgorizzo69 commented Aug 7, 2022

code423n4 commented Aug 1, 2022 •

edited