Server errors out when executing functions that return ()

[Abhiroop]

The problem seems to be with sending the bytestring over TCP. It encodes () as a message with size 0 and the receiving Client does not like this and crashes with the error

EnclaveIFC-exe: Network.Socket.recvBuf: invalid argument (non-positive length)

[Rewbert]

Lmao is this from the binary constraint? Sounds like a weird implementation choice of them

[Abhiroop]

Yeah, a silly implementation indeed. The Binary instance of () has this remark "The () type need never be written to disk: values of singleton type can be reconstructed from the type alone".

https://hackage.haskell.org/package/binary-0.8.9.1/docs/src/Data.Binary.Class.html#line-193

[Rewbert]

It's not wrong I guess, but in this case I guess we evaluate () for its side effects. Maybe we can give our own instance somehow

[Abhiroop]

Defining a new instance would be the principled approach but worth some hassle (construct your own newtype, etc). My makeshift patch was to send \0 whenever the result evaluates to (). If the client tries to decode this then of course a can of worms open

[Abhiroop]

Temp patch - f889f6a

[Abhiroop]

This 491d579 should allow removing the temp patch.

[Abhiroop]

(Needs testing before closing)