VTVL contest - peiw's results

Use a more recent version of Solidity.

• Use latest 0.8.17 for security. release note
• Instances: https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L2

Dont't use floating pragma

• Instance: https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/token/VariableSupplyERC20Token.sol#L2

Remove unnecessary commented code

• Instance: https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L135

++i costs less gas than i++, especially when in FOR loops.

• ++i costs less gas compared to i++ or i += 1 for unsigned integer, as pre-increment is cheaper (about 5 gas per iteration).
• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L353

Using unchecked blocks to save gas - increments in for loop can be unchecked (SAVE 30-40 GAS PER LOOP ITERATION).

• The majority of Solidity for loops increment a uint256 variable that starts at 0. These increment operations never need to be checked for over/underflow because the variable will never reach the max number of uint256 (will run out of gas long before that happens). The default over/underflow check wastes gas in every iteration of virtually every for loop .
• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L353

It costs more gas to initialize NON-CONSTANT/NON-IMMUTABLE variables to zero than to let the default of zero be applied.

• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L353
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L148
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L27

Usage of UINTS/INTS smaller than 32 bytes 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.
• Instances:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L27
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L148
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L176

!= is more efficient than > in require().

• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L257
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L449
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/token/FullPremintERC20Token.sol#L11

Use custom errors rather than REVERT()/REQUIRE() strings to save gas.

• Custom errors are available from solidity version 0.8.4. Custom errors save ~50 gas each time, they’re hitby avoiding having to allocate and store the revert string. Not defining the strings also save deployment gas.
• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L82

Splitting REQUIRE() statements that use && saves gas.

• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L344

x += y cost more gas than x = x + y for state variables.

• Instance:
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L179
  • https://github.com/code-423n4/2022-09-vtvl/blob/main/contracts/VTVLVesting.sol#L301