On Mon, Dec 05, 2005 at 09:19:05AM -0000, Simon Peyton-Jones wrote:
> Can you provide a small test case that demonstrates the crash?
Here it is:
import Control.Concurrent.STM
import System.IO.Unsafe (unsafePerformIO)
{-# NOINLINE var #-}
var :: TVar ()
var = unsafePerformIO (atomically (newTVar ()))
main = atomically (readTVar var)
I remember someone else posted a crash example with unsafeInterleaveIO.
> I think it's pretty unlikely that we'll support nested atomically (via
> unsafePerformIO) anytime soon.
OK, it's fine with me.
But maybe it would be easy to raise an exception in such scenario?
> UnsafePerformIO is, well, unsafe.
And so is unsafeInterleaveIO.
> I think you are really asking for some way to create top-level
> transactional variables?
Yes. Perhaps it would be easier to do it cleanly than arbitrary
top-level IO bindings?
In fact, almost every time I wanted a top-level unpure thingy, it was a
concurrency variable.
Best regards
Tomasz
--
I am searching for a programmer who is good at least in some of
[Haskell, ML, C++, Linux, FreeBSD, math] for work in Warsaw, Poland
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