Summary

Vulnerability Details

The instances below point to the second+ access of a state variable within a function. Caching of a state variable replaces each Gwarmaccess (100 gas) with a much cheaper stack read. Other less obvious fixes/optimizations include having local memory caches of state variable structs, or having local caches of state variable contracts/addresses.

More detail see this.

There are 3 instances of this issue:

• DSCEngine.s_collateralTokens should be cached with local memory-based variable in DSCEngine.getAccountCollateralValue(address), It is called more than once:

  • token = s_collateralTokens[i]

  • i < s_collateralTokens.length

• DSCEngine.s_collateralDeposited should be cached with local memory-based variable in DSCEngine.getAccountCollateralValue(address), It is called more than once:

  • amount = s_collateralDeposited[user][token]

• DSCEngine.i_dsc should be cached with local memory-based variable in DSCEngine._burnDsc(uint256,address,address), It is called more than once:

  • success = i_dsc.transferFrom(dscFrom,address(this),amountDscToBurn)

  • i_dsc.burn(amountDscToBurn)

Impact

Tools Used

Recommendations

Cache storage-based state variables in local memory-based variables appropriately to convert SLOADs to MLOADs and reduce gas consumption from 100 units to 3 units. than once for a function