Re: [Haskell-cafe] Brackets and Asynchronous Exceptions

Great. Thanks! This is exactly what I was looking for. Apparently this issue is also described in the paper Asynchronous Exception in Haskell. Thanks, Andrew On Wed, 15 Apr 2009, Jason Dagit wrote:

On Wed, Apr 15, 2009 at 4:06 PM, Andrew Gallagher wrote:

...

Hi,

In a program I am writing, I have many locations where I acquire a resource, perform an operation with it, then release it.  I have been using the 'bracket' function so that the "release" operation would be performed even if the operation threw an exception.  This seems to work nicely.

In the event of an asynchronous exception, however, is there a possible scenario where a release is not performed after an acquire?

Looking at the example given in bracket documentation:

bracket   (openFile "filename" ReadMode)   (hClose)   (\fileHandle -> do { ... })

Is it possbile that an asynchronous exception could be raised in this thread after openFile executes but *before* the appropriate handlers are installed and the operation is run, preventing hClose from executing?

If 'bracket' does not handle this case, should I be using the block/unblock functions to disable asynchronous exceptions:

block   (bracket      (openFile "filename" ReadMode)      (hClose)      (\fileHandle -> do         unblock         ({ ... })))

Does this answer your question? http://haskell.org/ghc/docs/latest/html/libraries/base/src/Control-Exception...

If so, I found it by going to haskell.org/hoogle searching for bracket and then following the haddock "Source" to the definition.

I hope that helps! Jason