base-4.3.1.0: Basic libraries

Portability | non-portable (requires concurrency)
Stability | provisional
Maintainer | ffi@haskell.org

Foreign.Concurrent

Contents

- Concurrency-based `ForeignPtr` operations

Description

FFI datatypes and operations that use or require concurrency (GHC only).

Synopsis

- newForeignPtr :: Ptr a -> IO () -> IO (ForeignPtr a)
- addForeignPtrFinalizer :: ForeignPtr a -> IO () -> IO ()

# 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 :: Ptr a -> IO () -> IO (ForeignPtr a)

Turns a plain memory reference into a foreign object by associating a finalizer - given by the monadic operation - with the reference. The finalizer will be executed after the last reference to the foreign object is dropped. There is no guarantee of promptness, and in fact there is no guarantee that the finalizer will eventually run at all.

addForeignPtrFinalizer :: ForeignPtr a -> IO () -> IO ()

This function adds a finalizer to the given `ForeignPtr`. The finalizer will run after the last reference to the foreign object is dropped, but before all previously registered finalizers for the same object.