/Haskell 8


Copyright (c) The University of Glasgow 2001
License BSD-style (see the file libraries/base/LICENSE)
Maintainer [email protected]
Stability provisional
Portability portable
Safe Haskell Unsafe
Language Haskell2010


The ForeignPtr type and operations. This module is part of the Foreign Function Interface (FFI) and will usually be imported via the Foreign module.

Unsafe API Only.

Unsafe low-level operations

unsafeForeignPtrToPtr :: ForeignPtr a -> Ptr a Source

This function extracts the pointer component of a foreign pointer. This is a potentially dangerous operations, as if the argument to unsafeForeignPtrToPtr is the last usage occurrence of the given foreign pointer, then its finalizer(s) will be run, which potentially invalidates the plain pointer just obtained. Hence, touchForeignPtr must be used wherever it has to be guaranteed that the pointer lives on - i.e., has another usage occurrence.

To avoid subtle coding errors, hand written marshalling code should preferably use withForeignPtr rather than combinations of unsafeForeignPtrToPtr and touchForeignPtr. However, the latter routines are occasionally preferred in tool generated marshalling code.

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Licensed under a BSD-style license (see top of the page).