[Haskell-cafe] IORef memory leak

[Don Stewart]

jsnow:
>
> I'm having some trouble with excessive memory use in a program that uses  
> a lot of IORefs.  I was able to write a much simpler program which  
> exhibits the same sort of behavior.  It appears that "modifyIORef" and  
> "writeIORef" leak memory; perhaps they keep a reference to the old  
> value.  I tried both ghc-6.8.3 and ghc-6.10.1.
>
> Is this a known limitation, or is this a ghc bug, or am I using IORefs  
> in the wrong way?
>
> -jim
>
>
> module Main where
>
> import Data.IORef
> import Control.Monad
>
> -- Leaks memory
> leakcheck1 ior =
> do go 1000000000
> where
>    go 0 = return ()
>    go n = do modifyIORef ior (+1)
>              go (n-1)

It is not possible to write a modifyIORef that *doesn't* leak memory!

-- Don