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code-423n4 / 2021-06-pooltogether-findings

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Gas savings of 300 by caching _currentAwardBalance in captureAwardBalance() #29

Open code423n4 opened 3 years ago

code423n4 commented 3 years ago

Handle

0xRajeev

Vulnerability details

Impact

Cache _currentAwardBalance state variable in a local variable for computation to save gas. 4 SLOADs + 1 SSTORE can be reduced to 1 SLOAD and 1 STORE.

Impact: Saves 300 gas from avoid 3 SLOADs because each SLOAD to already accessed storage slot costs 100.

Proof of Concept

2 SLOADs: https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L456

1 SSTORE + 1 SLOAD: https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L465

1 SLOAD: https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L470

Tools Used

Manual Analysis

Recommended Mitigation Steps

Cache _currentAwardBalance in a local variable in the beginning, use that for computation/return and one updation to state variable at the end.