Frax Ether Liquid Staking contest - dharma09's results

1.DEFAULT VALUE INITIALIZATION

PROBLEM

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

Instances include: ERC20PermitPermissionedMint.sol#L84 or use ++i instead of i++

  for (uint i; i < minters_array.length; ++i)

frxETHMinter.sol#L129

for (uint256 i; i < numDeposits; ++i)

OperatorRegistry.sol#L63 OperatorRegistry.sol#L84 OperatorRegistry.sol#L114

2.COMPARISONS: != IS MORE EFFICIENT THAN > IN REQUIRE (6 GAS LESS)

!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas)

For uints the minimum value would be 0 and never a negative value. Since it cannot be a negative value, then the check > 0 is essentially checking that the value is not equal to 0 therefore >0 can be replaced with !=0 which saves gas.

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.

PROOF OF CONCEPT

Instances include: frxETHMinter.sol#L126

require(numDeposits =! 0, "Not enough ETH in contract");

frxETHMinter.sol#L79

require(sfrxeth_recieved =! 0, 'No sfrxETH was returned');