[GHC] #7048: Add the ability to statically define a `FunPtr` to a haskell function

[GHC]

#7048: Add the ability to statically define a `FunPtr` to a haskell function
---------------------------------+------------------------------------------
    Reporter:  pcapriotti        |       Owner:                  
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:  7.8.1           
   Component:  Compiler          |     Version:  7.4.2           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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 Lauri Alanko [http://haskell.1045720.n5.nabble.com/Static-non-exported-
 stubs-td5713489.html suggests] that there should be a way to define a
 callback to a haskell function statically (i.e. without using a dynamic
 wrapper).

 It is currently possible to do so only by exporting the function and
 reimporting it as a function pointer:

 {{{
 foreign export ccall "my_callback" myCallback :: IO ()
 foreign import ccall "&my_callback" myCallbackPtr :: FunPtr (IO ())
 }}}

 but of course this not ideal because it creates an extra symbol (and is
 quirky).

 A possible new syntax could be:

 {{{
 foreign import ccall myCallbackPtr :: FunPtr (IO ()) = myCallback
 }}}

 or variations thereof. We probably want to keep `import` (rather than
 `export` or some new keyword), since this declaration brings something
 into scope, like a normal FFI import.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7048>
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