`XDEFIDistribution.sol#noReenter()` Switching between 1, 2 instead of 0, 1 is more gas efficient

[code423n4]

Handle

WatchPug

Vulnerability details

https://github.com/XDeFi-tech/xdefi-distribution/blob/3856a42df295183b40c6eee89307308f196612fe/contracts/XDEFIDistribution.sol#L51-L56

modifier noReenter() {
    require(_locked == 0, "LOCKED");
    _locked = uint256(1);
    _;
    _locked = uint256(0);
}

• SSTORE from 0 to 1 (or any non-zero value), the cost is 20000;
• SSTORE from 1 to 2 (or any other non-zero value), the cost is 5000.

By storing the original value once again, a refund is triggered (https://eips.ethereum.org/EIPS/eip-2200).

Since refunds are capped to a percentage of the total transaction's gas, it is best to keep them low, to increase the likelihood of the full refund coming into effect.

Therefore, switching between 1, 2 instead of 0, 1 will be more gas efficient.

See: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/86bd4d73896afcb35a205456e361436701823c7a/contracts/security/ReentrancyGuard.sol#L29-L33

[deluca-mike]

Agreed. Will do.

[deluca-mike]

Duplicate #1