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Exceptions 0.10.0 #61

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merged 3 commits into from
May 4, 2018
Merged

Exceptions 0.10.0 #61

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e1a7909
implement generalBracket
gelisam May 3, 2018
31e620a
implement uninterruptibleMask
gelisam May 3, 2018
a383136
exceptions >= 0.10.0
gelisam May 4, 2018
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4 changes: 2 additions & 2 deletions hint.cabal
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ test-suite unit-tests
directory,
filepath,
extensible-exceptions,
exceptions == 0.8.*
exceptions >= 0.10.0

if !os(windows) {
build-depends: unix >= 2.2.0.0
Expand All @@ -56,7 +56,7 @@ library
ghc-boot,
mtl,
filepath,
exceptions == 0.8.*,
exceptions == 0.10.*,
random,
directory

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15 changes: 14 additions & 1 deletion src/Control/Monad/Ghc.hs
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Expand Up @@ -60,7 +60,20 @@ instance (MonadIO m, MonadMask m) => MonadMask (GhcT m) where
wrap g = GhcT $ GHC.GhcT $ \s -> MTLAdapter (g s)
unwrap m = unMTLA . GHC.unGhcT (unGhcT m)

uninterruptibleMask = mask
uninterruptibleMask f = wrap $ \s ->
uninterruptibleMask $ \io_restore ->
unwrap (f $ \m -> (wrap $ \s' -> io_restore (unwrap m s'))) s
where
wrap g = GhcT $ GHC.GhcT $ \s -> MTLAdapter (g s)
unwrap m = unMTLA . GHC.unGhcT (unGhcT m)
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@gelisam gelisam May 3, 2018 •
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I also took the opportunity to fix the implementation of uninterruptibleMask. It was previously defined as uninterruptibleMask = mask, so calling uninterruptibleMask body was misleadingly running body in interruptible mode, not in uninterruptible mode. The difference is that some calls, like threadDelay, are intentionally marked as being interruptible even when running inside mask. As a result,

> timeout 1000000 $ mask_ $ threadDelay 3000000

terminates after 1 second because the timeout successfully interrupts the threadDelay after 1 second, while

> timeout 1000000 $ uninterruptibleMask_ $ threadDelay 3000000

terminates after 3 seconds, because the timeout has to wait until the uninterruptibleMask computation terminates before aborting the computation.

Without this fix,

> timeout 1000000 $ runGhcT ... $ mask_ $ lift $ threadDelay 3000000

and

> timeout 1000000 $ runGhcT ... $ uninterruptibleMask_ $ lift $ threadDelay 3000000

both terminate after 1 second, whereas with this fix, the second terminates after 3 seconds, as desired.


generalBracket acquire release body
= wrap $ \s -> generalBracket (unwrap acquire s)
(\a exitCase -> unwrap (release a exitCase) s)
(\a -> unwrap (body a) s)
where
wrap g = GhcT $ GHC.GhcT $ \s -> MTLAdapter (g s)
unwrap m = unMTLA . GHC.unGhcT (unGhcT m)
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This is the main fix: exceptions-0.9 introduced a new method named generalBracket, whose type I fixed in exceptions-0.10, so in order to upgrade from exceptions-0.8 to exceptions-0.10, we have to implement this method. If we wanted, we could add an #ifdef around this method definition in order to support both.

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What about depending on exceptions >= 0.8.0?

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Do you mean >= 0.10.0, or did you change your mind and now want an #ifdef in order to support both 0.8 and 0.10?

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I indeed meant >= 0.10.0 - thanks for spotting that. I would not bother supporting 0.8 and earlier, especially given how it's a v0, and how we're likely one of the last libraries to add support for the new exceptions versions.

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fixed, merging


instance (MonadIO m, MonadCatch m, MonadMask m) => GHC.ExceptionMonad (GhcT m) where
gcatch = catch
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