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-- A test to show that -XStaticPointers keeps generated CAFs alive.
{-# LANGUAGE StaticPointers #-}
module Main where
import GHC.StaticPtr
import Control.Concurrent
import Data.Maybe (fromJust)
import GHC.Fingerprint
import System.Mem
import System.Mem.Weak
import Unsafe.Coerce (unsafeCoerce)
nats :: [Integer]
nats = [0 .. ]
-- The key of a 'StaticPtr' to some CAF.
nats_key :: StaticKey
nats_key = staticKey (static nats :: StaticPtr [Integer])
main = do
let z = nats !! 400
print z
performGC
addFinalizer z (putStrLn "finalizer z")
print z
performGC
threadDelay 1000000
Just p <- unsafeLookupStaticPtr nats_key
print (deRefStaticPtr (unsafeCoerce p) !! 800 :: Integer)
-- Uncommenting the next line keeps 'nats' alive and would prevent a segfault
-- if 'nats' were garbage collected.
-- print (nats !! 900)
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