Beedle - Oracle free perpetual lending

Summary

Using storage instead of memory for structs/arrays saves gas.

Vulnerability Details

When fetching data from a storage location, assigning the data to a memory variable causes all fields of the struct/array to be read from storage, which incurs a Gcoldsload (2100 gas) for each field of the struct/array. If the fields are read from the new memory variable, they incur an additional MLOAD rather than a cheap stack read. Instead of declearing the variable with the memory keyword, declaring the variable with the storage keyword and caching any fields that need to be re-read in stack variables, will be much cheaper, only incuring the Gcoldsload for the fields actually read.

The only time it makes sense to read the whole struct/array into a memory variable, is if the full struct/array is being returned by the function, is being passed to a function that requires memory, or if the array/struct is being read from another memory array/struct (src).

Impact

There are 10 instances of this issue:

File: 2023-07-beedle/src/Lender.sol

Tools Used

Automated code review.

Recommendations

Consider using storage for struct/array.