Platform: Code4rena
Start Date: 03/05/2023
Pot Size: $60,500 USDC
Total HM: 25
Participants: 114
Period: 8 days
Judge: Picodes
Total Solo HM: 6
Id: 234
League: ETH
Rank: 51/114
Findings: 1
Award: $179.84
🌟 Selected for report: 0
🚀 Solo Findings: 0
🌟 Selected for report: JCN
Also found by: 0x73696d616f, 0xSmartContract, 0xnev, Audit_Avengers, Aymen0909, Blckhv, Eurovickk, K42, Kenshin, Rageur, Raihan, ReyAdmirado, SAAJ, SAQ, Shubham, Tomio, Walter, ayden, codeslide, descharre, dicethedev, hunter_w3b, j4ld1na, kaveyjoe, okolicodes, patitonar, petrichor, pontifex, yongskiws
179.8397 USDC - $179.84
Using the addition operator instead of plus-equals saves gas.
In Solididy, the opcode 'less or equal' doesn't exist. So the EVM will translate this by two distinct operation, first the inferior, and then the equal which cost more gas then a strict less.
Due to how constant variables are implemented (replacements at compile-time), an expression assigned to a constant variable is recomputed each time that the variable is used, which wastes some gas.
This saves deployment gas.
If the functions are required by an interface, the contract should inherit from that interface and use the override keyword.
++i costs less gas than i++, especially when it’s used in for-loops (—i/i— too). Saves 5 gas per loop.
Contracts are allowed to override their parents’ functions and change the visibility from external to public and can save gas by doing so.
Modifiers make code more elegant, but cost more than normal functions.
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. Each operation involving a uint8 costs an extra 22-28 gas (depending on whether the other operand is also a variable of type uint8) as compared to ones involving uint256, due to the compiler having to clear the higher bits of the memory word before operating on the uint8, as well as the associated stack operations of doing so. Use a larger size then downcast where needed.
assembly to write address storage valuesInstead of using address(this), it is more gas-efficient to pre-calculate and use the hardcoded address
Using nested is cheaper than using && multiple check combinations. There are more advantages, such as easier to read code and better coverage reports.
Use a solidity version of at least 0.8.0 to get overflow protection without SafeMath. Use a solidity version of at least 0.8.2 to get simple compiler automatic inlining. Use a solidity version of at least 0.8.3 to get better struct packing and cheaper multiple storage reads. Use a solidity version of at least 0.8.4 to get custom errors, which are cheaper at deployment than revert()/require() strings. 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.
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. Use uint256(1) and uint256(2) for true/false instead.
Use immutable if you want to assign a permanent value at construction. Use constants if you already know the permanent value. Both get directly embedded in bytecode, saving SLOAD. Variables only set in the constructor and never edited afterwards should be marked as immutable, as it would avoid the expensive storage-writing operation in the constructor (around 20 000 gas per variable) and replace the expensive storage-reading operations (around 2100 gas per reading) to a less expensive value reading (3 gas).
Uninitialized variables are assigned with the types default value. Explicitly initializing a variable with it’s default value costs unnecesary gas.
.call (bool success) transfer can be done gas-optimizedreturn data (bool success,) has to be stored due to EVM architecture, but in a usage in assembly, 'out' and 'outsize' values are given (0,0), this storage disappears and gas optimization is provided.
Use abi.encodePacked() where possible to save gas.
#0 - c4-judge
2023-05-17T10:45:22Z
Picodes marked the issue as grade-a