FIAT DAO veFDT contest - SooYa's results

> 0 IS LESS EFFICIENT THAN != 0 FOR UNSIGNED INTEGERS

Proof: While it may seem that > 0 is cheaper than !=, this is only true without the optimizer enabled and outside a require statement. If you enable the optimizer at 10k AND you’re in a require statement, this will save gas. You can see this tweet for more proofs:

https://twitter.com/gzeon/status/1485428085885640706

I suggest changing > 0 with != 0 here:

https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L412 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L448 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L469 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L502 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L564 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L635

LOOPS CAN BE OPTIMIZED IN SEVERAL WAYS

To optimize the for loop and make it consume less gas, i suggest to:

1. If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

2. Use ++i instead of i++, which is a cheaper operation (in this case there is no difference between i++ and ++i because we dont use the return value of this expression, which is the only difference between these two expression).

There are 4 instance for this issues:

https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L309 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L717 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L739 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L834

<x> += <Y> COSTS MORE GAS THAN <X> = <X> + <Y> FOR STATE VARIABLES

There are 11 instance for this issues:

https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L418 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L420 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L460 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L461 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L465 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L472 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L537 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L603 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L612 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L654 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L642

USING CALLDATA INSTEAD OF MEMORY FOR READ-ONLY ARGUMENTS IN EXTERNAL FUNCTIONS SAVES GAS

When a function with a memory array is called externally, the abi.decode() step has to use a for-loop to copy each index of the calldata to the memory index. Each iteration of this for-loop costs at least 60 gas (i.e. 60 * <mem_array>.length). Using calldata directly, obliviates the need for such a loop in the contract code and runtime execution.

If the array is passed to an internal function which passes the array to another internal function where the array is modified and therefore memory is used in the external call, it’s still more gass-efficient to use calldata when the external function uses modifiers, since the modifiers may prevent the internal functions from being called. Structs have the same overhead as an array of length one

There are 4 instances for this issues:

https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L825 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L597 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L224-L225 https://github.com/code-423n4/2022-08-fiatdao/blob/main/contracts/VotingEscrow.sol#L104-L105