X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fghci%2FRtClosureInspect.hs;h=e39a0bc7e324121d37247a282adad798ab926f54;hb=ed7788bce80decefd43aa9cadf2e6a2db0be38da;hp=c0b91405254d45cecc66447e32eddf81061766ea;hpb=a2a67cd520b9841114d69a87a423dabcb3b4368e;p=ghc-hetmet.git

diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs
index c0b9140..e39a0bc 100644
--- a/compiler/ghci/RtClosureInspect.hs
+++ b/compiler/ghci/RtClosureInspect.hs
@@ -74,7 +74,7 @@ import Data.Ix
 import Data.List
 import qualified Data.Sequence as Seq
 import Data.Monoid
-import Data.Sequence hiding (null, length, index, take, drop, splitAt, reverse)
+import Data.Sequence (viewl, ViewL(..))
 import Foreign
 -- import System.IO.Unsafe
 
@@ -654,11 +654,13 @@ cvObtainTerm hsc_env max_depth force old_ty hval = runTR hsc_env $ do
     clos <- trIO $ getClosureData a
     case tipe clos of
 -- Thunks we may want to force
--- NB. this won't attempt to force a BLACKHOLE.  Even with :force, we never
--- force blackholes, because it would almost certainly result in deadlock,
--- and showing the '_' is more useful.
       t | isThunk t && force -> traceTR (text "Forcing a " <> text (show t)) >>
                                 seq a (go (pred max_depth) my_ty old_ty a)
+-- Blackholes are indirections iff the payload is not TSO or BLOCKING_QUEUE.  So we
+-- treat them like indirections; if the payload is TSO or BLOCKING_QUEUE, we'll end up
+-- showing '_' which is what we want.
+      Blackhole -> do traceTR (text "Following a BLACKHOLE")
+                      appArr (go max_depth my_ty old_ty) (ptrs clos) 0
 -- We always follow indirections
       Indirection i -> do traceTR (text "Following an indirection" <> parens (int i) )
                           go max_depth my_ty old_ty $! (ptrs clos ! 0)
@@ -817,6 +819,7 @@ cvReconstructType hsc_env max_depth old_ty hval = runTR_maybe hsc_env $ do
   go my_ty a = do
     clos <- trIO $ getClosureData a
     case tipe clos of
+      Blackhole -> appArr (go my_ty) (ptrs clos) 0 -- carefully, don't eval the TSO
       Indirection _ -> go my_ty $! (ptrs clos ! 0)
       MutVar _ -> do
          contents <- trIO$ IO$ \w -> readMutVar# (unsafeCoerce# a) w