Phuture Finance contest - Tomio's results

1. Using multiple require() instead of && can save gas

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ChainlinkPriceOracle.sol#L86

Recommended Mitigation Steps: Change to:

	require(basePrice > 0, "ChainlinkPriceOracle: NEGATIVE");
	require(quotePrice > 0, "ChainlinkPriceOracle: NEGATIVE");

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2. Caching .length() for loop can save gas

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/IndexLogic.sol#L39 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/IndexLogic.sol#L60 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndexReweightingLogic.sol#L38 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndexReweightingLogic.sol#L50

Recommended Mitigation Steps: Change to:

	uint length = assets.length();
	for (uint i; i < length ; ++i) {

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3. Using != instead of > is more gas efficient

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/IndexLogic.sol#L76 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/IndexLogic.sol#L86 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/IndexLogic.sol#L98

Recommended Mitigation Steps: Change to:

	require(lastAssetBalanceInBase != 0, "Index: INSUFFICIENT_AMOUNT");

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4. Using unchecked and prefix increment can save gas

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndex.sol#L30

Recommended Mitigation Steps: Change to:

for (uint i; i < _assets.length;) {
            address asset = _assets[i];
            uint8 weight = _weights[i];

            weightOf[asset] = weight;
            assets.add(asset);

            emit UpdateAnatomy(asset, weight);
	unchecked{
		++i; //@audit-info: Place here with unchecked		
        }
    }

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5. Using += to increase value on var

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndexReweightingLogic.sol#L71

Recommended Mitigation Steps: Change to:

	_totalWeight += newWeight - prevWeight;

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6. Using if statement instead else if

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/TrackedIndexReweightingLogic.sol#L74-L78 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndexReweightingLogic.sol#L79-L83 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/ManagedIndexReweightingLogic.sol#L96

Recommended Mitigation Steps: Using if statement can save gas Change to:

		if (newShares > oldShares) {
                    orderer.addOrderDetails(orderId, asset, newShares - oldShares, IOrderer.OrderSide.Buy);
                } 
		if (oldShares > newShares) { //@audit-info: Replacing else if with if statement here
                    orderer.addOrderDetails(orderId, asset, oldShares - newShares, IOrderer.OrderSide.Sell);
                }

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7. Use immutable variables can save gas

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/PhuturePriceOracle.sol#L33 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/PhuturePriceOracle.sol#L24 https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/PhuturePriceOracle.sol#L27

Recommended Mitigation Steps: use immutable

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8. Gas improvement on calling SafeERC20.function

Proof of Concept: https://github.com/code-423n4/2022-04-phuture/blob/main/contracts/vToken.sol#L219

Recommended Mitigation Steps: by removing L#23 and directly call SafeERC20.function

Change to:

	SafeERC20.safeTransfer(asset, _recipient, Math.min(_amount, balance))

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