| Copyright | (c) The University of Glasgow 2001 |
|---|---|
| License | BSD-style (see the file libraries/base/LICENSE) |
| Maintainer | ffi@haskell.org |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Unsafe |
| Language | Haskell2010 |
Foreign.ForeignPtr.Unsafe
Contents
Description
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.
- unsafeForeignPtrToPtr :: ForeignPtr a -> Ptr a
Unsafe low-level operations
unsafeForeignPtrToPtr :: ForeignPtr a -> Ptr a
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.