standardtoken Code Style Findings

STA-01C: Redundant require Checks

Description:

The transferFrom function redundantly evaluates whether the _from address has sufficient balance to transfer as well as whether they have provided msg.sender with sufficient allowance. These checks are redundant as safe arithmetic subtractions are performed in the ensuing lines.

Example:

Copy
9function transferFrom(
10    address _from,
11    address _to,
12    uint256 _value
13) public returns (bool) {
14    require(_to != address(0),"To cannot be ZERO ADDRESS");
15    require(_from != address(0),"From cannot be Address 0");
16    require(_value <= balances[_from],"Insufficient Balance");
17    require(_value <= allowed[_from][msg.sender],"msg sender not approved of this amount");
18    balances[_from] = balances[_from] - _value;
19    balances[_to] = balances[_to] + _value;
20    allowed[_from][msg.sender] = allowed[_from][msg.sender] - _value;
21
22    emit Transfer(_from, _to, _value);
23    return true;
24}

Recommendation:

We advise either the require checks to be omitted or the subtractions to be performed in unchecked code blocks to ensure the code is gas optimal.

Alleviation:

Both subtractions are now optimally performed within an unchecked block.

STA-02C: Suboptimal Code

Description:

The linked subtraction is guaranteed to not underflow by the surrounding if block.

Example:

Copy
47if (_subtractedValue > oldValue) {
48    allowed[msg.sender][_spender] = 0;
49} else {
50    allowed[msg.sender][_spender] = oldValue - _subtractedValue;
51}

Recommendation:

We advise the subtraction to be set within an unchecked code block.

Alleviation:

The subtraction is now optimally performed in an unchecked block.