#2892: (threadDelay (-1)) hangs
-------------------------+--------------------------------------------------
Reporter: dancor | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.10.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Linux
Architecture: x86 |
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Changes (by igloo):
* difficulty: => Unknown
Old description:
> threadDelay silently hangs forever given a negative delay interval. It
> seems like this should at least be documented, but further is probably
> suboptimal magical behavior that leads to harder-to-find bugs; instead
> this should be an error. Conceivably threadDelay could take Maybe Int
> but that seems kind of out there.
>
> Here is some discussion from #haskell:
> 06:39 < dancor> do other ppl agree that (threadDelay (-1)) hanging
> silently is
> bug?
> 06:39 < dancor> i guess you might want infinite hang, hm
> 06:39 < Cale> dancor: I think I might agree with that, though now that
> you
> mention it, it's very handy.
> 06:39 < Cale> dancor: A lot of things which would cause a thread to block
> forever will throw an exception and kill the thread.
> 06:40 < Cale> (an exception which you'd often wish were silent)
> 06:40 < Cale> But threadDelay is the wrong place for that
> 06:40 < b_jonas> dancor: yeah, the thread should just be garbage-
> collected
> 06:42 * quicksilver uses "forever (threadDelay maxBound)"
>
> I'm on Debian lenny:
> ~ uname -a
> Linux pima 2.6.26-1-686-bigmem #1 SMP Sat Nov 8 19:46:36 UTC 2008 i686
> GNU/Linux
> ~ ghc --version
> The Glorious Glasgow Haskell Compilation System, version 6.10.1
> ~ cat threadHang.hs
> import Control.Concurrent
> main = threadDelay (-1)
New description:
threadDelay silently hangs forever given a negative delay interval. It
seems like this should at least be documented, but further is probably
suboptimal magical behavior that leads to harder-to-find bugs; instead
this should be an error. Conceivably threadDelay could take Maybe Int but
that seems kind of out there.
Here is some discussion from #haskell:
{{{
06:39 < dancor> do other ppl agree that (threadDelay (-1)) hanging
silently is
bug?
06:39 < dancor> i guess you might want infinite hang, hm
06:39 < Cale> dancor: I think I might agree with that, though now that you
mention it, it's very handy.
06:39 < Cale> dancor: A lot of things which would cause a thread to block
forever will throw an exception and kill the thread.
06:40 < Cale> (an exception which you'd often wish were silent)
06:40 < Cale> But threadDelay is the wrong place for that
06:40 < b_jonas> dancor: yeah, the thread should just be garbage-collected
06:42 * quicksilver uses "forever (threadDelay maxBound)"
}}}
I'm on Debian lenny:
{{{
~ uname -a
Linux pima 2.6.26-1-686-bigmem #1 SMP Sat Nov 8 19:46:36 UTC 2008 i686
GNU/Linux
~ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.10.1
~ cat threadHang.hs
import Control.Concurrent
main = threadDelay (-1)
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2892#comment:2>
GHC <http://www.haskell.org/ghc/>
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