gas improvement in withdraw & withdrawAll

[code423n4]

Handle

gpersoon

Vulnerability details

Impact

The functions withdraw and withdrawAll retrieve the value of marketIndexOfToken[token] twice.
The second time its stored in the variable marketIndex.
This could be optimized to save a bit of gas

Proof of Concept

// https://github.com/code-423n4/2021-08-floatcapital/blob/main/contracts/contracts/Staker.sol#L948

function withdraw(address token, uint256 amount) external {
ILongShort(longShort).updateSystemState(marketIndexOfToken[token]);
uint32 marketIndex = marketIndexOfToken[token];

function withdrawAll(address token) external {
ILongShort(longShort).updateSystemState(marketIndexOfToken[token]);
uint32 marketIndex = marketIndexOfToken[token];

Tools Used

Recommended Mitigation Steps

Replace:
ILongShort(longShort).updateSystemState(marketIndexOfToken[token]);
uint32 marketIndex = marketIndexOfToken[token];

With:
uint32 marketIndex = marketIndexOfToken[token];
ILongShort(longShort).updateSystemState(marketIndex);

[JasoonS]

This is our final fix. (so not relevant in our final code)