Values.hs

setValues state key file val = modifyVar_ state $ \vals -> do
    -- Force to make sure the old HashMap is not retained
    evaluate val
    let v = fmap toDyn val
    _ <- evaluate v
    let k = (file, Key key)

    weak <- case HMap.lookup k vals of
        Nothing -> pure Nothing
        Just v -> do
            evaluate v
            Just <$> mkWeakPtr v Nothing
    res <- evaluate $ HMap.insert k v vals

    performGC
    whenJust weak $ \w -> do
        b <- deRefWeak w
        when (isJust b) $
            print "DEREF VALUE STILL LIVES"

    -- This odd construction is required to prevent a space leak.
    -- We insert a fully evaluated value, but, somehow, the HashMap
    -- seems to keep track of the old value. I don't know how.
    -- Is there a space-leak in unordered-containers?
    -- The evaluate below fixes it, at the cost of walking the
    -- HashMap a second time.
    -- Without this evaluate, leaks of 30Mb/min have been observed.
    case HMap.lookup k res of
        Nothing -> pure ()
        Just v -> evaluate v >> pure () -- void $ evaluate v

    performGC
    whenJust weak $ \w -> do
        b <- deRefWeak w
        when (isJust b) $
            print "CONTINUES"

    return res