Frankencoin - pavankv's results

1 . check of minBid(challenge) must be first position in function:-

Summary In bid() first transfer the challengebid to challenger and then in line 216 checks the after all computation so it's good practice to check before transfer the challengebid and it's save gas also by avoid computation even the _bidAmountZCHF is lesser than minimumbid.

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/MintingHub.sol#L216

2. Instead of minterOnly() modifier use directly (if else) or (require) to check minter .

Summary :- In minterOnly() modifier calls isMinter() and isMinter(positions[msg.sender]) in if else statement to check whether the msg.sender is minter or not.

Modifiers can be used to:

Restrict access Validate inputs Guard against reentrancy hack

But isMinter() function only checks whether the msg.sender is minter or not return true or false . minterOnly() modifier checks true or false return by isMinter() function ,so instead of minterOnly() modifier we can use directly isMinter() in require or if else statement even it saves gas .

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Frankencoin.sol#L266 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Frankencoin.sol#L293

Recommendation :- require(isMinter(),"not minter"); if (!isMinter(msg.sender) && !isMinter(positions[msg.sender])) revert NotMinter();

Add above any one code in restricted function instead of minterOnly() modifier to save gas and reduce the code .

3 . Add alive() modifier in notifyChallengeSucceeded() function

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L329 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L366

1 . Directly call challenge.bid in minBid() to saves:-

In bid() function calls the minBid() public function with challenge variable which is initialise by storage only , in minBid() public function uses challenges storage variable array to search given challenge variable which is already found in bid() only then it calls minBid() internal function , in this it will again initialise from storage only, to get challenge.bid .But we can absorb here challenge variable which is already initialise from storage in bid() and try search again and initialise in minBid() functions from storage again .

So Sload consumes 200-800 gas each time , if challenges[] arrays grows large then it consumes 800 gas .

Recommedation :- try to directly call minBid(challenge.bid) in bid() and in internal minBid(challenge.bid) also which saves the gas cost .

change to :- in bid() minBid(challenge.bid)

in minBid( uint challengeBid) public function /// minBid(challenge.bid)

in minBid(uint challengeBid) internal function /// minBid(challenge.bid) // to calculate the minimum bid .

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/MintingHub.sol#L216

2.Functions guaranteed to revert when called by normal users can be marked payable

If a function modifier such as onlyOwner is used, the function will revert if a normal user tries to pay the function. Marking the function as payable will lower the gas cost for legitimate callers because the compiler will not include checks for whether a payment was provided. The extra opcodes avoided are CALLVALUE(2),DUP1(3),ISZERO(3),PUSH2(3),JUMPI(10),PUSH1(3),DUP1(3),REVERT(0),JUMPDEST(1),POP(2).

Saves 21 gas per call

code snippet :- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L132 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L159 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L227 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L249 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L292

3 . use Ternary operate to save gas :-

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L250 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L121 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L160 https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L184

4 .Multiple address mappings can be combined into a single mapping of an address to a struct, where appropriate

Saves a storage slot for the mapping. Depending on the circumstances and sizes of types, can avoid a Gsset (20000 gas) per mapping combined. Reads and subsequent writes can also be cheaper when a function requires both values and they both fit in the same storage slot. Finally, if both fields are accessed in the same function, can save ~42 gas per access due to not having to recalculate the key’s keccak256 hash (Gkeccak256 - 30 gas) and that calculation’s associated stack operations.

saves 42 per access

code snippet:- https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/MintingHub.sol#L37