Gas Optimizations

[code423n4]

[01] Use != 0 instead of > 0 to save gas.

For unsigned integer types, comparisons with != 0 are cheaper then with > 0.

There are 3 instances of this issue.

File: contracts/gateway/L1GraphTokenGateway.sol
201: require(_amount > 0, "INVALID_ZERO_AMOUNT");
217: require(maxSubmissionCost > 0, "NO_SUBMISSION_COST");

File: contracts/l2/gateway/L2GraphTokenGateway.sol
146: require(_amount > 0, "INVALID_ZERO_AMOUNT");

[02] Update to solidity >= 0.8.4 and use custom errors rather than require/revert strings to save gas

Custom errors are available from solidity version 0.8.4 and can save ~50 gas each time they’re hit by avoiding having to allocate and store the revert string. Not defining the strings also save deployment gas.

There are 56 instances of this issue.

File: contracts/gateway/GraphTokenGateway.sol
31: require(_newPauseGuardian != address(0), "PauseGuardian must be set");
40: require(!_paused, "Paused (contract)");

File: contracts/gateway/L1GraphTokenGateway.sol
74: require(inbox != address(0), "INBOX_NOT_SET");
78: require(msg.sender == address(bridge), "NOT_FROM_BRIDGE");
82: require(l2ToL1Sender == l2Counterpart, "ONLY_COUNTERPART_GATEWAY");
110: require(_inbox != address(0), "INVALID_INBOX");
111: require(_l1Router != address(0), "INVALID_L1_ROUTER");
122: require(_l2GRT != address(0), "INVALID_L2_GRT");
132: require(_l2Counterpart != address(0), "INVALID_L2_COUNTERPART");
142: require(_escrow != address(0) && Address.isContract(_escrow), "INVALID_ESCROW");
153: require(_newWhitelisted != address(0), "INVALID_ADDRESS");
154: require(!callhookWhitelist[_newWhitelisted], "ALREADY_WHITELISTED");
165: require(_notWhitelisted != address(0), "INVALID_ADDRESS");
166: require(callhookWhitelist[_notWhitelisted], "NOT_WHITELISTED");
200: require(_l1Token == address(token), "TOKEN_NOT_GRT");
201: require(_amount > 0, "INVALID_ZERO_AMOUNT");
202: require(_to != address(0), "INVALID_DESTINATION");
217: require(maxSubmissionCost > 0, "NO_SUBMISSION_COST");
224: require(msg.value >= expectedEth, "WRONG_ETH_VALUE");
271: require(_l1Token == address(token), "TOKEN_NOT_GRT");
275: require(_amount <= escrowBalance, "BRIDGE_OUT_OF_FUNDS");

File: contracts/governance/Governed.sol
24: require(msg.sender == governor, "Only Governor can call");
41: require(_newGovernor != address(0), "Governor must be set");

File: contracts/governance/Managed.sol
44: require(!controller.paused(), "Paused");
45: require(!controller.partialPaused(), "Partial-paused");
49: require(!controller.paused(), "Paused");
53: require(msg.sender == controller.getGovernor(), "Caller must be Controller governor");
57: require(msg.sender == address(controller), "Caller must be Controller");
104: require(_controller != address(0), "Controller must be set");

File: contracts/l2/gateway/L2GraphTokenGateway.sol
98: require(_l2Router != address(0), "INVALID_L2_ROUTER");
108: require(_l1GRT != address(0), "INVALID_L1_GRT");
118: require(_l1Counterpart != address(0), "INVALID_L1_COUNTERPART");
145: require(_l1Token == l1GRT, "TOKEN_NOT_GRT");
146: require(_amount > 0, "INVALID_ZERO_AMOUNT");
147: require(msg.value == 0, "INVALID_NONZERO_VALUE");
148: require(_to != address(0), "INVALID_DESTINATION");
153: require(outboundCalldata.extraData.length == 0, "CALL_HOOK_DATA_NOT_ALLOWED");
233: require(_l1Token == l1GRT, "TOKEN_NOT_GRT");
234: require(msg.value == 0, "INVALID_NONZERO_VALUE");

File: contracts/l2/token/GraphTokenUpgradeable.sol
60: require(isMinter(msg.sender), "Only minter can call");
94: require(_owner == recoveredAddress, "GRT: invalid permit");
95: require(_deadline == 0 || block.timestamp <= _deadline, "GRT: expired permit");
106: require(_account != address(0), "INVALID_MINTER");
115: require(_minters[_account], "NOT_A_MINTER");
123: require(_minters[msg.sender], "NOT_A_MINTER");

File: contracts/l2/token/L2GraphToken.sol
36: require(msg.sender == gateway, "NOT_GATEWAY");
49: require(_owner != address(0), "Owner must be set");
60: require(_gw != address(0), "INVALID_GATEWAY");
70: require(_addr != address(0), "INVALID_L1_ADDRESS");

File: contracts/upgrades/GraphProxy.sol
105: require(_newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
141: require(Address.isContract(_pendingImplementation), "Implementation must be a contract");
157: require(msg.sender != _admin(), "Cannot fallback to proxy target");
179: revert(ptr, size)

File: contracts/upgrades/GraphProxyStorage.sol
62: require(msg.sender == _admin(), "Caller must be admin");

File: contracts/upgrades/GraphUpgradeable.sol
24: require(msg.sender == _proxy.admin(), "Caller must be the proxy admin");
32: require(msg.sender == _implementation(), "Caller must be the implementation");

[03] Don’t compare boolean expressions to boolean literals

if ( == true) => if (), if ( == false) => if (!)

There's 1 instance of this issue.

File: contracts/gateway/L1GraphTokenGateway.sol
214: extraData.length == 0 || callhookWhitelist[msg.sender] == true,