Tracer contest - hrkrshnn's results

Handle

hrkrshnn

Vulnerability details

Impact

Several variables can be converted into immutables. Doing so can save 2100 gas for storage reads when the slot is warm and 100 otherwise.

Notice: Variable declaration can be converted into an immutable.
  --> @openzeppelin/contracts/token/ERC20/ERC20.sol:38:5:
   |
38 |     uint256 private _totalSupply;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Insurance.sol:18:5:
   |
18 |     ITracerPerpetualsFactory public perpsFactory;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Insurance.sol:20:5:
   |
20 |     address public collateralAsset; // Address of collateral asset
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Insurance.sol:23:5:
   |
23 |     address public token; // token representation of a users holding in the pool
   |     ^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Insurance.sol:25:5:
   |
25 |     ITracerPerpetualSwaps public tracer; // Tracer associated with Insurance Pool
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Liquidation.sol:28:5:
   |
28 |     IPricing public pricing;
   |     ^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Liquidation.sol:29:5:
   |
29 |     ITracerPerpetualSwaps public tracer;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Liquidation.sol:30:5:
   |
30 |     address public insuranceContract;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Liquidation.sol:31:5:
   |
31 |     address public fastGasOracle;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Pricing.sol:17:5:
   |
17 |     address public tracer;
   |     ^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Pricing.sol:18:5:
   |
18 |     IInsurance public insurance;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^


Notice: Variable declaration can be converted into an immutable.
  --> contracts/Pricing.sol:19:5:
   |
19 |     IOracle public oracle;
   |     ^^^^^^^^^^^^^^^^^^^^^

Proof of Concept

References to source file and line numbers can be seen above.

Tools Used

A custom solidity compiler.

Recommended Mitigation Steps

As explained above, these variables can be converted into immutables.

Handle

hrkrshnn

Vulnerability details

Impact

Gas optimization.

Use at least 0.8.4 instead of 0.8.0

It has an important optimization improvement: a low level inliner. Especially since you have several small functions.

The current hardhat config indicates that version 0.8.0 is being used.

Handle

hrkrshnn

Vulnerability details

Impact

Gas optimization.

For function arguments, change memory to calldata

There are several places where this is applicable, however, will point out one such occasion:

modified   src/contracts/Trader.sol
@@ -64,7 +64,7 @@ contract Trader is ITrader {
      * @param makers An array of signed make orders
      * @param takers An array of signed take orders
      */
-    function executeTrade(Types.SignedLimitOrder[] memory makers, Types.SignedLimitOrder[] memory takers)
+    function executeTrade(Types.SignedLimitOrder[] calldata makers, Types.SignedLimitOrder[] calldata takers)
         external
         override
     {
@@ -144,7 +144,7 @@ contract Trader is ITrader {
      * @dev Should only be called with a verified signedOrder and with index
      *      < signedOrders.length
      */
-    function grabOrder(Types.SignedLimitOrder[] memory signedOrders, uint256 index)
+    function grabOrder(Types.SignedLimitOrder[] calldata signedOrders, uint256 index)
         internal
         returns (Perpetuals.Order memory)
     {

Reason: when you specify memory for a (non value type) function-parameter for an external function, the following happens: the compiler would copy elements from calldata to memory (using the opcode calldatacopy.) Then later on, the internal call (here grabOrder) would pass a memory reference. However, this is a great example of where copying to memory is unnecessary. Note that there is also the opcode calldataload to read an offset from calldata. By changing the location from memory to calldata, you avoid this expensive copy from calldata to memory, while managing to do exactly what's needed.

You would only have to use memory if the function has to modify the parameter, in which case a copy is really needed as calldata cannot be modified.