Platform: Code4rena
Start Date: 08/03/2023
Pot Size: $60,500 USDC
Total HM: 2
Participants: 123
Period: 7 days
Judge: hansfriese
Id: 220
League: ETH
Rank: 115/123
Findings: 1
Award: $19.30
🌟 Selected for report: 0
🚀 Solo Findings: 0
🌟 Selected for report: JCN
Also found by: 0x1f8b, 0xSmartContract, 0xSolus, 0xhacksmithh, 0xnev, Angry_Mustache_Man, Aymen0909, Diana, Flora, Inspex, Madalad, MatricksDeCoder, MiniGlome, R-Nemes, RaymondFam, ReyAdmirado, Rolezn, SAAJ, Sathish9098, Shubham, Udsen, Viktor_Cortess, arialblack14, atharvasama, ayden, c3phas, carlitox477, descharre, dharma09, durianSausage, fatherOfBlocks, ginlee, glcanvas, hunter_w3b, leopoldjoy, matrix_0wl, mrpathfindr, nadin, oyc_109, pipoca, schrodinger, slvDev, ulqiorra, volodya
19.3029 USDC - $19.30
| Index | Issue | Instances |
|---|---|---|
| GAS-1 | Avoid contract existence checks by using low level calls | 18 |
| GAS-2 | <x> += <y> costs more gas than <x> = <x> + <y> for state variables | 22 |
| GAS-3 | Optimize names to save gas | 2 |
| GAS-4 | Using calldata instead of memory in external functions saves gas | 9 |
| GAS-5 | Multiple accesses of a mapping/array should use a local variable cache | 24 |
| GAS-6 | State variables should be cached in stack variables rather than re-reading them from storage | 8 |
Total 83 instances found in 6 issues
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external function calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value. Similar behavior can be achieved in earlier versions by using low-level calls, since low level calls never check for contract existence
Instances (18):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/BYTES2.sol#L96
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/BYTES2.sol#L101
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/BYTES2.sol#L120
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L632
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L640
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L666
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L773
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L774
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L802
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L803
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L948
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L949
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L974
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1026
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1226
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1506
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1571
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1673
Using the addition operator instead of plus-equals saves 113 gas
Instances (22):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L977
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1029
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1630
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1627
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1626
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1332
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1580
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1515
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1078
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1079
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1080
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1099
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1100
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1101
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1160
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1161
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1164
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1283
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1292
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1298
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1343
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1357
public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted.
Instances (2):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/BYTES2.sol#L34
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L188
When a function with a memory array is called externally, the abi.decode() step has to use a for-loop to copy each index of the calldata to the memory index. Each iteration of this for-loop costs at least 60 gas (i.e. 60 * <mem_array>.length). Using calldata directly, obliviates the need for such a loop in the contract code and runtime execution. Note that even if an interface defines a function as having memory arguments, it’s still valid for implementation contracs to use calldata arguments instead.
Instances (9):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1739
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1740
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1761
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1762
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1763
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1784
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1785
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1803
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1820
The instances below point to the second+ access of a value inside a mapping/array, within a function. Caching a mapping’s value in a local storage or calldata variable when the value is accessed multiple times, saves ~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. Caching an array’s struct avoids recalculating the array offsets into memory/calldata
Instances (24):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L716
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L717
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L733
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L734
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L974
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1026
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1279
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1288
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1215
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1210
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1837
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1834
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1823
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1320
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1144
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1145
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1148
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1158
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1160
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1161
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1298
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1824
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1825
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1830
The instances below point to the second+ access of a state variable within a function. Caching of a state variable replaces each Gwarmaccess (100 gas) with a much cheaper stack read. Other less obvious fixes/optimizations include having local memory caches of state variable structs, or having local caches of state variable contracts/addresses.
Instances (10):
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L718
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L735
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1280
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1289
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1313
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1770
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1788
https://github.com/code-423n4/2023-03-neotokyo/blob/main/contracts/staking/NeoTokyoStaker.sol#L1831
#0 - c4-judge
2023-03-17T04:23:57Z
hansfriese marked the issue as grade-b