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Inefficient Use of uint32/uint64 Types

Description​

In Solidity, uint256 is the most efficient data type in terms of gas usage because it is directly supported by the Ethereum Virtual Machine (EVM). On the other hand, uint32 and uint64 require additional bytecode to pack and unpack the values, making them less gas efficient.

Example Code​

contract GasInefficient {
    uint32 public num1;
    uint256 public num2;

    function storeNums(uint32 _num1, uint256 _num2) public {
        num1 = _num1;
        num2 = _num2;
    }
}

Recommendation​

It is recommended to use uint256 data type whenever possible for the storage and manipulation of integers in Solidity contracts. However, if the range of the integer value is known and falls within uint32 or uint64, then it is safe to use those data types. It is important to note that using smaller data types may save a small amount of storage space, but can result in higher gas costs. Therefore, it is best to weigh the trade-off between storage space and gas efficiency before choosing a data type.