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G-01 ++i costs less gas than i++, especially when it's used in for loops
G-02 Use nested multiple require instead of && operator
G-03 Use custom errors rather than revert()/require() strings to save deployment gas
G-04 Comparison operators
G-05 Use a more recent version of solidity
G-06 += costs more gas than = + for state variables
G-07 Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
G-08 Using private rather than public for constants saves gas
G-09 calldata instead of memory for read-only function parameter
G-10 ++i/i++ should be unchecked{++i}/unchecked{i++}
G-11 .length should not be looked up in every loop of a for-loop
G-12 internal functions only called once can be inlined to save gas
G-13 Using > 0 costs more gas than != 0 when used on a uint in a require() statement
G-14 Empty blocks should be removed or emit something
G-15 Using bools for storage incurs overhead
G-16 Using storage instead of memory for structs/arrays saves gas
G-01 ++i costs less gas than i++, especially when it's used in for loops
G-03 Use custom errors rather than revert()/require() strings to save deployment gas
Custom errors from Solidity 0.8.4 are cheaper than require strings (cheaper deployment cost and runtime cost when the revert condition is met) while providing the same amount of information, as explained here https://blog.soliditylang.org/2021/04/21/custom-errors/
Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).
In the EVM, there is no opcode for >= or <=. When using greater than or equal, two operations are performed: > and =.
Using strict comparison operators hence saves gas.
Mitigation:
Replace <= with <, and >= with >. Do not forget to increment/decrement the compared variable
example:
-require(maxFee >= minFee, Error.INVALID_AMOUNT);
+require(maxFee > minFee - 1, Error.INVALID_AMOUNT);
G-05 Use a more recent version of solidity
Use a solidity version of at least 0.8.10 to have external calls skip contract existence checks if the external call has a return value
Use a solidity version of at least 0.8.12 to get string.concat() instead of abi.encodePacked(,)
Use a solidity version of at least 0.8.13 to get the ability to use using for with a list of free functions
G-07 Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size. https://docs.soliditylang.org/en/v0.8.11/internals/layout_in_storage.html
Use a larger size then downcast where needed
G-08 Using private rather than public for constants saves gas
If needed, the value can be read from the verified contract source code. Savings are due to the compiler not having to create non-payable getter functions for deployment calldata, and not adding another entry to the method ID table.
G-09 calldata instead of memory for read-only function parameter
If a reference type function parameter is read-only, it is cheaper in gas to use calldata instead of memory.
Calldata is a non-modifiable, non-persistent area where function arguments are stored, and behaves mostly like memory.
Try to use calldata as a data location because it will avoid copies and also makes sure that the data cannot be modified.
G-11 .length should not be looked up in every loop of a for-loop
The overheads outlined below are PER LOOP, excluding the first loop
storage arrays incur a Gwarmaccess (100 gas)
memory arrays use MLOAD (3 gas)
calldata arrays use CALLDATALOAD (3 gas)
Caching the length changes each of these to a DUP (3 gas), and gets rid of the extra DUP needed to store the stack offset.
G-14 Empty blocks should be removed or emit something
The code should be refactored such that they no longer exist, or the block should do something useful, such as emitting an event or reverting. If the contract is meant to be extended, the contract should be abstract and the function signatures be added without any default implementation. If the block is an empty if-statement block to avoid doing subsequent checks in the else-if/else conditions, the else-if/else conditions should be nested under the negation of the if-statement, because they involve different classes of checks, which may lead to the introduction of errors when the code is later modified (if(x){}else if(y){...}else{...} => if(!x){if(y){...}else{...}})
Mitigation:
Use uint256(1) and uint256(2) for true/false to avoid a Gwarmaccess (100 gas) for the extra SLOAD, and to avoid Gsset (20000 gas) when changing from ‘false’ to ‘true’, after having been ‘true’ in the past
G-16 Using storage instead of memory for structs/arrays saves gas
When fetching data from a storage location, assigning the data to a memory variable causes all fields of the struct/array to be read from storage, which incurs a Gcoldsload (2100 gas) for each field of the struct/array.
If the fields are read from the new memory variable, they incur an additional MLOAD rather than a cheap stack read.
Instead of declearing the variable with the memory keyword, declaring the variable with the storage keyword and caching any fields that need to be re-read in stack variables, will be much cheaper, only incuring the Gcoldsload for the fields actually read.
The only time it makes sense to read the whole struct/array into a memory variable, is if the full struct/array is being returned by the function, is being passed to a function that requires memory, or if the array/struct is being read from another memory array/struct
G-17 Multiple address mappings can be combined into a single mapping of an address to a struct, where appropriate
Saves a storage slot for the mapping. Depending on the circumstances and sizes of types, can avoid a Gsset (20000 gas) per mapping combined. Reads and subsequent writes can also be cheaper when a function requires both values and they both fit in the same storage slot.
Finally, if both fields are accessed in the same function, can save ~42 gas per access due to not having to recalculate the key’s keccak256 hash (Gkeccak256 - 30 gas) and that calculation’s associated stack operations.
Table of Contents:
G-01 ++i costs less gas than i++, especially when it's used in for loops
G-02 Use nested multiple require instead of && operator
G-03 Use custom errors rather than revert()/require() strings to save deployment gas
G-04 Comparison operators
G-05 Use a more recent version of solidity
G-06 += costs more gas than = + for state variables
G-07 Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
G-08 Using private rather than public for constants saves gas
G-09 calldata instead of memory for read-only function parameter
G-10 ++i/i++ should be unchecked{++i}/unchecked{i++}
G-11 .length should not be looked up in every loop of a for-loop
G-12 internal functions only called once can be inlined to save gas
G-13 Using > 0 costs more gas than != 0 when used on a uint in a require() statement
G-14 Empty blocks should be removed or emit something
G-15 Using bools for storage incurs overhead
G-16 Using storage instead of memory for structs/arrays saves gas
G-01 ++i costs less gas than i++, especially when it's used in for loops
There are 8 instances:
HomeFiProxy.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L87
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L136
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L248
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L311
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L322
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L603
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L624
Tasks.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L181
G-02 Use nested multiple require instead of && operator
Require statements including conditions with the && operator can be broken down in multiple require statements to save gas.
There is 1 instance:
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L353-L357
G-03 Use custom errors rather than revert()/require() strings to save deployment gas
Custom errors from Solidity 0.8.4 are cheaper than require strings (cheaper deployment cost and runtime cost when the revert condition is met) while providing the same amount of information, as explained here
https://blog.soliditylang.org/2021/04/21/custom-errors/
Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).
There are 68 instances:
DebtToken.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L33
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L50
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L96
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L104
ProjectFactory.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol#L36
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol#L66
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol#L84
HomeFiProxy.so
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L41
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L81
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L105
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L133
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L39
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L46
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L52
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L61
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L106
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L183
HomeFi.so
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L73
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L78
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L84
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L142
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L191
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L255
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L123
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L132
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L135
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L150
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L153
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L166
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L176
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L191
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L195
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L201
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L238
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L241
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L245
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L277
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L303
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L308
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L341
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L369
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L406
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L511
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L525
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L530
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L753
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L888
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L908
Community.so
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L69
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L75
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L83
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L92
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L133
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L161
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L193
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L237
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L248
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L253
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L314
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L349
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L356
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L386
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L408
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L493
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L536
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L557
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L764
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L792
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L888
Tasks.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L44
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L50
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L58
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L124
G-04 Comparison operators
In the EVM, there is no opcode for >= or <=. When using greater than or equal, two operations are performed: > and =.
Using strict comparison operators hence saves gas.
There are 14 instances:
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L107
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L200
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L368
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L438
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L608
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L614
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L650
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L655
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L661
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L710
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L354
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L355
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L401
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L792
Mitigation:
Replace <= with <, and >= with >. Do not forget to increment/decrement the compared variable
example:
-require(maxFee >= minFee, Error.INVALID_AMOUNT);
+require(maxFee > minFee - 1, Error.INVALID_AMOUNT);
G-05 Use a more recent version of solidity
Use a solidity version of at least 0.8.10 to have external calls skip contract existence checks if the external call has a return value
Use a solidity version of at least 0.8.12 to get string.concat() instead of abi.encodePacked(,)
Use a solidity version of at least 0.8.13 to get the ability to use using for with a list of free functions
There are 9 instances:
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L3
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L3
G-06 += costs more gas than = + for state variables (also -= vs = - )
There are 9 instances:
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L289
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L179
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L250
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L290
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L440
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L711
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L423
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L435
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L83
G-07 Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size.
https://docs.soliditylang.org/en/v0.8.11/internals/layout_in_storage.html
Use a larger size then downcast where needed
There are 9 instances:
DebtToken.so
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L16
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L47
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L82
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L100
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L103
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L107
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L507
SignatureDecoder.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L29
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L65
G-08 Using private rather than public for constants saves gas
If needed, the value can be read from the verified contract source code. Savings are due to the compiler not having to create non-payable getter functions for deployment calldata, and not adding another entry to the method ID table.
There is 1 instance:
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L60
G-09 calldata instead of memory for read-only function parameter
If a reference type function parameter is read-only, it is cheaper in gas to use calldata instead of memory.
Calldata is a non-modifiable, non-persistent area where function arguments are stored, and behaves mostly like memory.
Try to use calldata as a data location because it will avoid copies and also makes sure that the data cannot be modified.
There are 13 instances:
DebtToken.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L45
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol#L46
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L236
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L254
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L268
HomeFi.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L210
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L284
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L878
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L488
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L761
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L874
SignatureDecoder.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L22
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L61
G-10 ++i/i++ should be unchecked{++i}/unchecked{i++} when it is not possible for them to overflow, as is the case when used in for- and while-loops
The unchecked keyword is new in solidity version 0.8.0, so this only applies to that version or higher, which these instances are.
This saves 30-40 gas per loop: https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#the-increment-in-for-loop-post-condition-can-be-made-unchecked
There are 8 instances:
HomeFiProxy.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L87
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L136
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L248
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L311
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L322
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L603
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L624
Tasks.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L181
G-11 .length should not be looked up in every loop of a for-loop
The overheads outlined below are PER LOOP, excluding the first loop
storage arrays incur a Gwarmaccess (100 gas)
memory arrays use MLOAD (3 gas)
calldata arrays use CALLDATALOAD (3 gas)
Caching the length changes each of these to a DUP (3 gas), and gets rid of the extra DUP needed to store the stack offset.
There is 1 instance:
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L603
G-12 internal functions only called once can be inlined to save gas
Not inlining costs 20 to 40 gas because of two extra JUMP instructions and additional stack operations needed for function calls.
There are 23 instances:
HomeFiProxy.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L197-L200
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L216-L219
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L236-L238
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L254-L256
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L268-L270
HomeFi.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L284-L287
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L303-L308
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L314-L319
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L747-L751
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L791-L793
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L830-L834
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L875-L880
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L757-L762
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L824-L828
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L899-L904
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L910-L915
SignatureDecoder.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L20-L24
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L43-L47
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/SignatureDecoder.sol#L61-L69
Tasks.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L106-L109
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L119-L122
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L175-L179
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L191-L195
G-13 Using > 0 costs more gas than != 0 when used on a uint in a require() statement
This change saves 6 gas per instance.
https://aws1.discourse-cdn.com/business6/uploads/zeppelin/original/2X/3/363a367d6d68851f27d2679d10706cd16d788b96.png
There are 10 instances:
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L107
HomeFi.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L245
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L195
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L380
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L601
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L601
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L261
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L427
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L764
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L840
G-14 Empty blocks should be removed or emit something
The code should be refactored such that they no longer exist, or the block should do something useful, such as emitting an event or reverting. If the contract is meant to be extended, the contract should be abstract and the function signatures be added without any default implementation. If the block is an empty if-statement block to avoid doing subsequent checks in the else-if/else conditions, the else-if/else conditions should be nested under the negation of the if-statement, because they involve different classes of checks, which may lead to the introduction of errors when the code is later modified (if(x){}else if(y){...}else{...} => if(!x){if(y){...}else{...}})
There is 1 instance:
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L88
G-15 Using bools for storage incurs overhead
Booleans are more expensive than uint256 or any type that takes up a full word because each write operation emits an extra SLOAD to first read the slot's contents, replace the bits taken up by the boolean, and then write back.
This is the compiler's defense against contract upgrades and pointer aliasing, and it cannot be disabled.
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/58f635312aa21f947cae5f8578638a85aa2519f5/contracts/security/ReentrancyGuard.sol#L23-L27
There are 9 instances:
HomeFiProxy.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L30
Disputes.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L144
HomeFi.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L50
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L68
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L69
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L156
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L582
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L750
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L55
Mitigation:
Use uint256(1) and uint256(2) for true/false to avoid a Gwarmaccess (100 gas) for the extra SLOAD, and to avoid Gsset (20000 gas) when changing from ‘false’ to ‘true’, after having been ‘true’ in the past
G-16 Using storage instead of memory for structs/arrays saves gas
When fetching data from a storage location, assigning the data to a memory variable causes all fields of the struct/array to be read from storage, which incurs a Gcoldsload (2100 gas) for each field of the struct/array.
If the fields are read from the new memory variable, they incur an additional MLOAD rather than a cheap stack read.
Instead of declearing the variable with the memory keyword, declaring the variable with the storage keyword and caching any fields that need to be re-read in stack variables, will be much cheaper, only incuring the Gcoldsload for the fields actually read.
The only time it makes sense to read the whole struct/array into a memory variable, is if the full struct/array is being returned by the function, is being passed to a function that requires memory, or if the array/struct is being read from another memory array/struct
There are 2 instances:
Community.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L619
Project.sol
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L591
G-17 Multiple address mappings can be combined into a single mapping of an address to a struct, where appropriate
Saves a storage slot for the mapping. Depending on the circumstances and sizes of types, can avoid a Gsset (20000 gas) per mapping combined. Reads and subsequent writes can also be cheaper when a function requires both values and they both fit in the same storage slot.
Finally, if both fields are accessed in the same function, can save ~42 gas per access due to not having to recalculate the key’s keccak256 hash (Gkeccak256 - 30 gas) and that calculation’s associated stack operations.
There are 2 instances:
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L64-L66
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L59-L61
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