ghc-internal-9.1001.0: Basic libraries
Copyright(C) 2014 I/O Tweag
Licensesee libraries/base/LICENSE
Portabilitynon-portable (GHC Extensions)
Safe HaskellNone



Symbolic references to values.

References to values are usually implemented with memory addresses, and this is practical when communicating values between the different pieces of a single process.

When values are communicated across different processes running in possibly different machines, though, addresses are no longer useful since each process may use different addresses to store a given value.

To solve such concern, the references provided by this module offer a key that can be used to locate the values on each process. Each process maintains a global table of references which can be looked up with a given key. This table is known as the Static Pointer Table. The reference can then be dereferenced to obtain the value.

The various communicating processes need to agree on the keys used to refer to the values in the Static Pointer Table, or lookups will fail. Only processes launched from the same program binary are guaranteed to use the same set of keys.



data StaticPtr a Source #

A reference to a value of type a.


Instances details
IsStatic StaticPtr Source #

@since base-

Instance details

Defined in GHC.Internal.StaticPtr

deRefStaticPtr :: StaticPtr a -> a Source #

Dereferences a static pointer.

type StaticKey = Fingerprint Source #

A key for StaticPtrs that can be serialized and used with unsafeLookupStaticPtr.

staticKey :: StaticPtr a -> StaticKey Source #

The StaticKey that can be used to look up the given StaticPtr.

unsafeLookupStaticPtr :: StaticKey -> IO (Maybe (StaticPtr a)) Source #

Looks up a StaticPtr by its StaticKey.

If the StaticPtr is not found returns Nothing.

This function is unsafe because the program behavior is undefined if the type of the returned StaticPtr does not match the expected one.

data StaticPtrInfo Source #

Miscellaneous information available for debugging purposes.





Instances details
Show StaticPtrInfo Source #

@since base-

Instance details

Defined in GHC.Internal.StaticPtr

staticPtrKeys :: IO [StaticKey] Source #

A list of all known keys.

class IsStatic (p :: Type -> Type) where Source #

A class for things buildable from static pointers.

GHC wraps each use of the static keyword with fromStaticPtr. Because the static keyword requires its argument to be an instance of Typeable, fromStaticPtr carries a Typeable constraint as well.


fromStaticPtr :: Typeable a => StaticPtr a -> p a Source #


Instances details
IsStatic StaticPtr Source #

@since base-

Instance details

Defined in GHC.Internal.StaticPtr