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{-# LANGUAGE Trustworthy #-}{-# LANGUAGE NoImplicitPrelude #-}------------------------------------------------------------------------------- |-- Module      :  Foreign.Concurrent-- Copyright   :  (c) The University of Glasgow 2003-- License     :  BSD-style (see the file libraries/base/LICENSE)---- Maintainer  :  ffi@haskell.org-- Stability   :  provisional-- Portability :  non-portable (requires concurrency)---- FFI datatypes and operations that use or require concurrency (GHC only).-------------------------------------------------------------------------------moduleForeign.Concurrent(-- * Concurrency-based 'ForeignPtr' operations-- | These functions generalize their namesakes in the portable-- "Foreign.ForeignPtr" module by allowing arbitrary 'IO' actions-- as finalizers.  These finalizers necessarily run in a separate-- thread, cf. /Destructors, Finalizers and Synchronization/,-- by Hans Boehm, /POPL/, 2003.newForeignPtr,addForeignPtrFinalizer,)whereimportGHC.IO(IO)importGHC.Ptr(Ptr)importGHC.ForeignPtr(ForeignPtr)importqualifiedGHC.ForeignPtrnewForeignPtr::Ptra->IO()->IO(ForeignPtra)---- ^Turns a plain memory reference into a foreign object by-- associating a finalizer - given by the monadic operation - with the-- reference.  The storage manager will start the finalizer, in a-- separate thread, some time after the last reference to the-- @ForeignPtr@ is dropped.  There is no guarantee of promptness, and-- in fact there is no guarantee that the finalizer will eventually-- run at all.---- Note that references from a finalizer do not necessarily prevent-- another object from being finalized.  If A's finalizer refers to B-- (perhaps using 'touchForeignPtr', then the only guarantee is that-- B's finalizer will never be started before A's.  If both A and B-- are unreachable, then both finalizers will start together.  See-- 'touchForeignPtr' for more on finalizer ordering.--newForeignPtr=GHC.ForeignPtr.newConcForeignPtraddForeignPtrFinalizer::ForeignPtra->IO()->IO()-- ^This function adds a finalizer to the given @ForeignPtr@.  The-- finalizer will run /before/ all other finalizers for the same-- object which have already been registered.---- This is a variant of @Foreign.ForeignPtr.addForeignPtrFinalizer@,-- where the finalizer is an arbitrary @IO@ action.  When it is-- invoked, the finalizer will run in a new thread.---- NB. Be very careful with these finalizers.  One common trap is that-- if a finalizer references another finalized value, it does not-- prevent that value from being finalized.  In particular, 'Handle's-- are finalized objects, so a finalizer should not refer to a 'Handle'-- (including @stdout@, @stdin@ or @stderr@).--addForeignPtrFinalizer=GHC.ForeignPtr.addForeignPtrConcFinalizer