I am just writing to see if Zeppelin had discontinued support for upgradable Libraries in Solidity or if not, whether they would even solve my use case
Right now, we would just love a sub-set of our contracts functionality to be isolated.
The functionality will ideally accept a storage struct as an arg so we can access an internal mapping. A library seems like a perfect use case for this - however we would love for it to be upgradable. Past the blog post (https://medium.com/zeppelin-blog/proxy-libraries-in-solidity-79fbe4b970fd) in 2017.. I can't see anything from Zeppelin on this. Is it possible? Does it function just the same as a regular solidity lib? Would some special delegateCall needed on the sending side to access storage, or is it even possible through a proxy contract?
After that 2017 post by @maraoz we didnāt develop the idea any further, so we donāt have an offering that you would be able to use out of the box.
Note that any implementation of an upgradeable library requires a CALL operation in order to find out which is the current library address, because of the way storage and DELEGATECALL interact. This implies that there will be a base cost of 700 (the cost of a CALL) in any such implementation, which makes the gas overhead comparable to a normal proxy contract.
I agree though that the gas savings of passing storage args might be greater.
I hope all is well settling in to Berlin life.