Gas savings by removing state variable baseline in Vader.sol

[code423n4]

Handle

0xRajeev

Vulnerability details

Impact

From Solidity’s documentation (https://docs.soliditylang.org/en/v0.8.4/contracts.html#constant-and-immutable-state-variables), “State variables can be declared as constant or immutable. In both cases, the variables cannot be modified after the contract has been constructed. For constant variables, the value has to be fixed at compile-time, while for immutable, it can still be assigned at construction time. The compiler does not reserve a storage slot for these variables, and every occurrence is replaced by the respective value. Compared to regular state variables, the gas costs of constant and immutable variables are much lower.”

State variable baseline is initialized the value of _1m in constructor and then is never modified. Replacing its use directly by a constant_1m avoids a storage slot and associated SLOADs (2600 gas) leading to gas savings.

Proof of Concept

https://github.com/code-423n4/2021-04-vader/blob/3041f20c920821b89d01f652867d5207d18c8703/vader-protocol/contracts/Vader.sol#L25

https://github.com/code-423n4/2021-04-vader/blob/3041f20c920821b89d01f652867d5207d18c8703/vader-protocol/contracts/Vader.sol#L63

https://github.com/code-423n4/2021-04-vader/blob/3041f20c920821b89d01f652867d5207d18c8703/vader-protocol/contracts/Vader.sol#L218-L219

Tools Used

Manual Analysis

Recommended Mitigation Steps

Remove baseline state variable and replace its use directly by a constant_1m