Gas Optimizations

[code423n4]

USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE() STRINGS TO SAVE GAS

Custom Errors can be implemented as such:

INBOX_NOT_SET(); NOT_FROM_BRIDGE(); ONLY_COUNTERPART_GATEWAY(); INVALID_INBOX(); INVALID_L1_ROUTER(); INVALID_L2_GRT(); INVALID_ESCROW(); INVALID_ADDRESS(); ALREADY_WHITELISTED(); NOT_WHITELISTED(); TOKEN_NOT_GRT(): INVALID_ZERO_AMOUNT(); INVALID_DESTINATION(); CALL_HOOK_DATA_NOT_ALLOWED(); TOKEN_NOT_GRT(); BRIDGE_OUT_OF_FUNDS();

While REVERT() statements can be also used to replace REQUIRE() statements like this i.e.:

gateway/L1GraphTokenGateway.sol

• Use if(inbox == address(0)) revert INBOX_NOT_SET(); instead of require(inbox != address(0), "INBOX_NOT_SET");
• Use if(msg.sender != address(bridge)) revert NOT_FROM_BRIDGE(); instead of require(inbox != address(0), "INBOX_NOT_SET");
• Use if(l2ToL1Sender != l2Counterpart) revert ONLY_COUNTERPART_GATEWAY(); instead of require(inbox != address(0), "INBOX_NOT_SET");

MORE REQUIRE STATEMENTS INSTEAD OF ‘&&’

Require statements including conditions with the && operator can be broken down in multiple require statements to save gas.

Instances Found:

• gateway/L1GraphTokenGateway.sol#L142 Remedy: Use require(_escrow != address(0), "INVALID_ESCROW"); require(Address.isContract(_escrow), "INVALID_ESCROW"); instead of require(_escrow != address(0) && Address.isContract(_escrow), "INVALID_ESCROW");