#10460: Allow foreign prim to return Any -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: | -------------------------------------+------------------------------------- Comment (by simonpj): Generally ok but * The ability to pass `Any` to `foreign import prim` is not documented in [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ffi.html #ffi-prim 8.1.3 of the user manual], and it jolly well should be. If you want to extend this to arbitrary FFI imports then we should document that too. * Who converts the argument to `Any`? The caller? With `unsafeCoerce`? * You should never combine a '''safe''' foreign import with `Any`. "Safe" means that the call may block and GC may happen, so passing a pointer into the heap is a bad idea. (And this constraint should be documented.) Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10460#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler