Gas Optimizations

[code423n4]

Gas

[G-01] Unnecessary variable assignment.

Impact

If a variable is not set/initialized, it is assumed to have the default value (0, false, 0x0 etc depending on the data type). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

Proof of Concept

  NotionalTradeModule.sol::238 => for(uint256 i = 0; i < modules.length; i++) {
  NotionalTradeModule.sol::254 => for(uint256 i = 0; i < modules.length; i++) {
  NotionalTradeModule.sol::393 => for(uint256 i = 0; i < positionsLength; i++) {
  NotionalTradeModule.sol::519 => uint32 minImpliedRate = 0;
  NotionalTradeModule.sol::605 => for(uint256 i = 0; i < positionsLength; i++) {
  NotionalTradeModule.sol::618 => for(uint256 i = 0; i < positionsLength; i++) {

Recommendation

Remove explicit zero initialization.

[G-02] Contracts using unlocked pragma.

Impact

Contracts in scope use pragma solidity ^0.8.0, allowing wide enough range of versions.

Proof of Concept

  wfCashERC4626.sol::2 => pragma solidity ^0.8.0;

Recommendation

Consider locking compiler version, for example pragma solidity 0.8.6. This can have additional benefits, for example using custom errors to save gas and so forth.

[G-03] Reduce the size of error messages (Long revert Strings).

Impact

Shortening revert strings to fit in 32 bytes will decrease deployment time gas and will decrease runtime gas when the revert condition is met. Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

Proof of Concept

  NotionalTradeModule.sol::169 => require(_setToken.isComponent(address(_sendToken)), "Send token must be an index component");
  NotionalTradeModule.sol::199 => require(_setToken.isComponent(address(wrappedfCash)), "FCash to redeem must be an index component");
  NotionalTradeModule.sol::378 => require(wrappedfCashAddress.isContract(), "WrappedfCash not deployed for given parameters");
  NotionalTradeModule.sol::573 => require(_paymentToken == assetToken, "Token is neither asset nor underlying token");

Recommendation

Shorten the revert strings to fit in 32 bytes, or use custom errors if >0.8.4.

[G-04] Cache Array Length Outside of Loop.

Impact

Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack. Caching the array length in the stack saves around 3 gas per iteration.

Proof of Concept

  NotionalTradeModule.sol::238 => for(uint256 i = 0; i < modules.length; i++) {
  NotionalTradeModule.sol::254 => for(uint256 i = 0; i < modules.length; i++) {

Recommendation

Store the array’s length in a variable before the for-loop.

[G-05] ++i costs less gas compared to i++ or i += 1

Impact

++i costs less gas compared to i++ or i += 1 for unsigned integer, as pre-increment is cheaper (about 5 gas per iteration). This statement is true even with the optimizer enabled.

Proof of Concept

  NotionalTradeModule.sol::238 => for(uint256 i = 0; i < modules.length; i++) {
  NotionalTradeModule.sol::254 => for(uint256 i = 0; i < modules.length; i++) {
  NotionalTradeModule.sol::393 => for(uint256 i = 0; i < positionsLength; i++) {
  NotionalTradeModule.sol::605 => for(uint256 i = 0; i < positionsLength; i++) {
  NotionalTradeModule.sol::618 => for(uint256 i = 0; i < positionsLength; i++) {

Recommendation

Use ++i instead of i++ to increment the value of an uint variable. Same thing for --i and i--.

Tools used

c4udit, manual