0 is less efficient than != 0 for unsigned integers (with proof)
!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas) Proof: While it may seem that > 0 is cheaper than !=, this is only true without the optimizer enabled and outside a require statement. If you enable the optimizer at 10k AND you’re in a require statement, this will save gas. You can see this tweet for more proofs: https://twitter.com/gzeon/status/1485428085885640706
PuttyV2.sol:293: require(order.baseAsset.code.length > 0, "baseAsset is not contract");
PuttyV2.sol:598: require(token.code.length > 0, "ERC20: Token is not contract");
PuttyV2.sol:599: require(tokenAmount > 0, "ERC20: Amount too small");
PuttyV2.sol:556: for (uint256 i = 0; i < orders.length; i++) {
PuttyV2.sol:594: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:611: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:627: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:637: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:647: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:658: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:670: for (uint256 i = 0; i < whitelist.length; i++) {
PuttyV2.sol:728: for (uint256 i = 0; i < arr.length; i++) {
PuttyV2.sol:742: for (uint256 i = 0; i < arr.length; i++) {
3. Variables: No need to explicitly initialize variables with default values
If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.
We can use uint number; instead of uint number = 0;
I suggest removing explicit initializations for default values.
4. An array’s length should be cached to save gas in for-loops
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.
PuttyV2.sol:556: for (uint256 i = 0; i < orders.length; i++) {
PuttyV2.sol:594: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:611: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:627: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:637: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:647: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:658: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:670: for (uint256 i = 0; i < whitelist.length; i++) {
PuttyV2.sol:728: for (uint256 i = 0; i < arr.length; i++) {
PuttyV2.sol:742: for (uint256 i = 0; i < arr.length; i++) {
Remediation:
Here, I suggest storing the array’s length in a variable before the for-loop, and use it instead.
5. ++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
PuttyV2.sol:556: for (uint256 i = 0; i < orders.length; i++) {
PuttyV2.sol:594: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:611: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:627: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:637: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:647: for (uint256 i = 0; i < assets.length; i++) {
PuttyV2.sol:658: for (uint256 i = 0; i < floorTokens.length; i++) {
PuttyV2.sol:670: for (uint256 i = 0; i < whitelist.length; i++) {
PuttyV2.sol:728: for (uint256 i = 0; i < arr.length; i++) {
PuttyV2.sol:742: for (uint256 i = 0; i < arr.length; i++) {
1. !=0 instead of >0 for UINT
Instances
PuttyV2.sol #L293 PuttyV2.sol #L598 PuttyV2.sol #L599
Reference:
https://twitter.com/gzeon/status/1485428085885640706
Remediation:
I suggest changing > 0 with != 0. Also, please enable the Optimizer.
2. ++i costs less gas than i++, especially when it’s used in for-loops (--i/i-- too)
Saves 6 gas PER LOOP
Instances:
PuttyV2.sol #L556 PuttyV2.sol #L594 PuttyV2.sol #L611 PuttyV2.sol #L627 PuttyV2.sol #L637 PuttyV2.sol #L647 PuttyV2.sol #L658 PuttyV2.sol #L670 PuttyV2.sol #L728 PuttyV2.sol #L742
Reference:
https://code4rena.com/reports/2022-05-cally#g-19-i-costs-less-gas-than-i-especially-when-its-used-in-for-loops---ii---too
3. Variables: No need to explicitly initialize variables with default values
If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.
We can use
uint number;instead ofuint number = 0;Instance Includes:
PuttyV2.sol #L497
Recommendation:
I suggest removing explicit initializations for default values.
4. An array’s length should be cached to save gas in for-loops
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.
Instances:
PuttyV2.sol #L556 PuttyV2.sol #L594 PuttyV2.sol #L611 PuttyV2.sol #L627 PuttyV2.sol #L637 PuttyV2.sol #L647 PuttyV2.sol #L658 PuttyV2.sol #L670 PuttyV2.sol #L728 PuttyV2.sol #L742
Remediation:
Here, I suggest storing the array’s length in a variable before the for-loop, and use it instead.
5. ++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
Instances:
PuttyV2.sol #L556 PuttyV2.sol #L594 PuttyV2.sol #L611 PuttyV2.sol #L627 PuttyV2.sol #L637 PuttyV2.sol #L647 PuttyV2.sol #L658 PuttyV2.sol #L670 PuttyV2.sol #L728 PuttyV2.sol #L742
Reference:
https://code4rena.com/reports/2022-05-cally#g-11-ii-should-be-uncheckediuncheckedi-when-it-is-not-possible-for-them-to-overflow-as-is-the-case-when-used-in-for--and-while-loops