Wow, this looks like a bug to me. If it's not a bug, then it's horribly
unintuitive.
I extended your example in an effort to figure out what was going on.
Apparently weak pointers loath live IORefs:
import Data.IORef
import Data.Maybe
import System.Mem
import System.Mem.Weak
import Control.Monad
> Could mkWeakPair do what you want?
> http://haskell.org/ghc/docs/latest/html/libraries/base/System-Mem-Weak.html#v:mkWeakPair
No, it's just a convenience function that doesn't help much, because the
value already refers to the IORef anyway.
Here's a minimal example to illustrate the problem:
im
Could mkWeakPair do what you want?
http://haskell.org/ghc/docs/latest/html/libraries/base/System-Mem-Weak.html#v:mkWeakPair
Or are you trying to do something else?
- Job
2009/11/2 Patai Gergely
> Hello all,
>
> I wanted to create a weak pointer with an IORef as the key and something
> else as
> Is the IORef or the value in the IORef your key?
I want the IORef itself to be the key. However, that doesn't work with
optimisations turned on (the pointers get wiped out at the first gc), I
guess because they remove the box around the MutVar#. Extracting that
MutVar# seems to solve the problem.
Is the IORef or the value in the IORef your key?
2009/11/2 Patai Gergely
> Hello all,
>
> I wanted to create a weak pointer with an IORef as the key and something
> else as the value, but I saw no way to do it through the API provided.
> After some experimentation I came up with the following ab
Hello all,
I wanted to create a weak pointer with an IORef as the key and something
else as the value, but I saw no way to do it through the API provided.
After some experimentation I came up with the following abomination for
a solution:
myWeakRef (IORef (STRef r)) v f =
IO $ \s -> case mkWeak
