Gas Optimizations

[code423n4]

Using bools for storage incurs overhead

    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/58f635312aa21f947cae5f8578638a85aa2519f5/contracts/security/ReentrancyGuard.sol#L23-L27

mapping(bytes32 => mapping(address => bool)) internal deprecatedRegistryContracts;         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L60

mapping(bytes32 => mapping(address => bool)) private _deprecatedSchainToERC20;         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L44

mapping(bytes32 => bool) public activeEthTransfers;           

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxEth.sol#L43

mapping(bytes32 => mapping(address => bool)) private _deprecatedSchainToERC1155;         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L47

mapping(bytes32 => mapping(address => bool)) private _deprecatedSchainToERC721;         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L44

mapping(bytes32 => bool) private _interchainConnections;           

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L47

bool public override messageInProgress;            

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L77

mapping(bytes32 => bool) private _automaticDeploy;           

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBox.sol#L39

mapping(address => mapping(bytes32 => bool)) public activeUsers;         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/CommunityPool.sol#L47

abi.encode() is less efficient than abi.encodePacked()

data = abi.encode(receiver, tokenId, tokenURI);           

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/extensions/ERC721ReferenceMintAndMetadataSchain.sol#L72

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L213

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L240

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L261

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L309

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L341

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L374

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L426

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L459

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L494

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L528

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L566

return abi.encode(message);              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L593

require() strings longer than 32 bytes cost extra gas

require(hasRole(EXTRA_CONTRACT_REGISTRAR_ROLE, msg.sender), "EXTRA_CONTRACT_REGISTRAR_ROLE is required");                   

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L125

require(hasRole(CONSTANT_SETTER_ROLE, msg.sender), "Not enough permissions to set constant");                

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L133

require(!_getRegistryContracts()[bytes32(0)].contains(extraContract), "Extra contract is already registered");                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L174

require(connectedChains[dstChainHash].inited, "Destination chain is not initialized");                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L240

require(connectedChains[targetChainHash].inited, "Destination chain is not initialized");                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L291

require(!_getRegistryContracts()[chainHash].contains(extraContract), "Extra contract is already registered");                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L365

"Extra contract is already registered for all chains"                

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L368

"Destination contract is not a contract"                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L426

"Sender contract is not registered"                   

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L489

"DepositBox was not approved for ERC20 token"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L110

"Not enough money to finish this transaction"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxEth.sol#L102

"DepositBox was not approved for ERC1155 token"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L114

"DepositBox was not approved for ERC1155 token Batch"                

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L156

return bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"));                      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L333

return bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"));                      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L352

"DepositBox was not approved for ERC721 token"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L107

revert("Already killed or incorrect sender");                   

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L135

require(address(newCommunityPoolAddress) != address(0), "CommunityPool address has to be set");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L152

"Not enough permissions to register extra contract"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L169

require(schainHash != MAINNET_HASH, "Schain hash can not be equal Mainnet");              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L171

"Not enough permissions to register extra contract"                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L189

require(schainHash != MAINNET_HASH, "Schain hash can not be equal Mainnet");              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L191

require(_checkSchainBalance(fromSchainHash), "Schain wallet has not enough funds");                 

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L217

"Starting counter is not equal to incoming message counter");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L222

require(keccak256(abi.encodePacked(schainName)) != MAINNET_HASH, "Schain id can not be equal Mainnet");              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L320

"Sender contract is not registered"                   

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L331

"SKALE chain name cannot be Mainnet"                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBox.sol#L66

require(contractReceiver != address(0), "Incorrect address of contract receiver on Schain");              

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Twin.sol#L66

"../schain/tokens/ERC721OnChain.sol";                       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/extensions/ERC721ReferenceMintAndMetadataMainnet.sol#L26#Limport

"../schain/tokens/ERC721OnChain.sol";                       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/extensions/ERC721ReferenceMintAndMetadataSchain.sol#L26#Limport

require(getMessageType(data) == MessageType.TRANSFER_ERC20, "Message type is not ERC20 transfer");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L270

"Message type is not ERC20 transfer and total supply"               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L283

"Message type is not ERC20 transfer with token info"               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L321

require(getMessageType(data) == MessageType.TRANSFER_ERC721, "Message type is not ERC721 transfer");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L351

"Message type is not ERC721 transfer with token info"               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L386

require(getMessageType(data) == MessageType.INTERCHAIN_CONNECTION, "Message type is not Interchain connection");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L438

require(getMessageType(data) == MessageType.TRANSFER_ERC1155, "Message type is not ERC1155 transfer");               

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L469

"Message type is not ERC1155AndTokenInfo transfer"                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L506

"Message type is not ERC1155Batch transfer"                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L540

"Message type is not ERC1155BatchAndTokenInfo transfer"                  

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/Messages.sol#L578

Using > 0 costs more gas than != 0 when used on uints in a require() statement

require(approveTransfers[msg.sender] > 0, "User has insufficient ETH");         

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxEth.sol#L122

<array>.length should not be looked up in every loop of a for-loop

Even memory arrays incur the overhead of bit tests and bit shifts to calculate the array length

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L515

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L76

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L79

for (uint256 i = 0; i < ids.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L275

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L444

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L459

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L76

for (uint i = 0; i < schainContracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L100

for (uint i = 0; i < length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L149

for (uint i = 0; connected && i < length; i++) {    

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L175

for (uint256 i = 0; i < contracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L118

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L235

++i/i++ should be unchecked{++i}/unchecked{++i} when it is not possible for them to overflow, as is the case when used in for- and while-loops

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L221

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L515

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L76

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L276

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L79

for (uint256 i = 0; i < ids.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L275

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L398

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L444

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L459

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L76

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L260

for (uint i = 0; i < schainContracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L100

for (uint i = 0; i < length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L149

for (uint i = 0; connected && i < length; i++) {    

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L175

for (uint256 i = 0; i < contracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L118

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L235

++i costs less gas than ++i, especially when it's used in for-loops (--i/i-- too)

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L221

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L515

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L76

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L276

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L79

for (uint256 i = 0; i < ids.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L275

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L398

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L444

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L459

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L76

for (uint256 i = from; i < to; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L260

for (uint i = 0; i < schainContracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L100

for (uint i = 0; i < length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L149

for (uint i = 0; connected && i < length; i++) {    

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L175

for (uint256 i = 0; i < contracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L118

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L235

It costs more gas to initialize variables to zero than to let the default of zero be applied

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/MessageProxy.sol#L515

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L76

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L79

for (uint256 i = 0; i < ids.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L275

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L444

for (uint256 i = 0; i < ids.length; i++)       

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC1155.sol#L459

for (uint256 i = 0; i < tokens.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC721.sol#L76

for (uint i = 0; i < schainContracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L100

for (uint i = 0; i < length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L149

for (uint i = 0; connected && i < length; i++) {    

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/Linker.sol#L175

for (uint256 i = 0; i < contracts.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L118

uint notReimbursedGas = 0;            

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L234

for (uint256 i = 0; i < messages.length; i++) {      

https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/MessageProxyForMainnet.sol#L235

[yavrsky]

Only marginal gas improvements.

[GalloDaSballo]

Using bools for storage incurs overhead

Per the rationale 100 gas per bool used 8 * 100 = 800 (removed the non mapping as a toggle probably can't be optimized)

abi.encode() is less efficient than abi.encodePacked()

In lack of any detail am non counting this, would recommend the warden to always explain why something works

require() strings longer than 32 bytes cost extra gas

Per the discussion in #30 2500 per string, will also cap at 25 findings, some of the linked strings are random strings 25 * 2500 = 62500

Using > 0 costs more gas than != 0 when used on uints in a require() statement

3 gas

.length should not be looked up in every loop of a for-loop

3 gas per check * 12 times = 36

++i/i++ should be unchecked{++i}/unchecked{++i} when it is not possible for them to overflow, as is the case when used in for- and while-loops

22 gas per instance * 16 = 352

++i costs less gas than ++i, especially when it's used in for-loops (--i/i-- too)

Will ignore per the above

It costs more gas to initialize variables to zero than to let the default of zero be applied

3 gas per instance * 13 = 39

[GalloDaSballo]

Total: 63730