main.nim

import dynlib

type
  setupProc = proc (toCall: proc(): string) {.nimcall.}
  callProc = proc () {.nimcall.}


var
  dll: LibHandle
  setup: setupProc
  call: callProc
  theValue = 2

proc myProc(): string =
  theValue += 1
  return "Something cool"

dll = loadLib("./liblib.so")
if dll != nil:
  let setupAddr = dll.symAddr("setup")
  if setupAddr != nil:
    setup = cast[setupProc](setupAddr)
  let callAddr = dll.symAddr("call")
  if callAddr != nil:
    call = cast[callProc](callAddr)

if setup != nil:
  setup(myProc)
  call()
  call()
  call()
  echo theValue
else:
  echo "Wasn't able to load setup() from DLL."