passing by reference... my darkest enemy
actual reason below:
In your case (without reference) the compiler generates a temporary object (int) for the first argument of your MyApplication constructor. You pass this temporary int to QApplication’s constructor (with int reference), which saves the address of this reference. Once your MyApplication constructor is done the temporary int is destroyed but QApplication still has its address.
{-# LANGUAGE CPP #-}
module Opts
(
getOpts,
) where
import System.Environment
import System.Console.GetOpt
import Data.Maybe ( fromMaybe )
-------------------
import CoreTypes
import Utils
options :: [OptDescr (ServerInfo -> ServerInfo)]
options = [
Option "p" ["port"] (ReqArg readListenPort "PORT") "listen on PORT",
Option "d" ["dedicated"] (ReqArg readDedicated "BOOL") "start as dedicated (True or False)"
]
readListenPort
, readDedicated
:: String -> ServerInfo -> ServerInfo
readListenPort str opts = opts{listenPort = readPort}
where
readPort = fromInteger $ fromMaybe 46631 (maybeRead str :: Maybe Integer)
readDedicated str opts = opts{isDedicated = readDed}
where
readDed = fromMaybe True (maybeRead str :: Maybe Bool)
getOpts :: ServerInfo -> IO ServerInfo
getOpts opts = do
args <- getArgs
case getOpt Permute options args of
(o, [], []) -> return $ foldr ($) opts{runArgs = args} o
(_,_,errs) -> ioError (userError (concat errs ++ usageInfo header options))
where header = "Usage: hedgewars-server [OPTION...]"