From: Simon Marlow <simonmar@microsoft.com>
Date: Wed, 16 May 2007 13:35:13 +0000 (+0000)
Subject: add a comment
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=5c04842774b5ca60292762a9c89c23263496a556

add a comment
---

diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs
index e7c85c9..f289b14 100644
--- a/compiler/ghci/RtClosureInspect.hs
+++ b/compiler/ghci/RtClosureInspect.hs
@@ -504,6 +504,9 @@ cvObtainTerm hsc_env force mb_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 -> seq a $ go tv ty a
 -- We always follow indirections 
       Indirection _ -> go tv ty $! (ptrs clos ! 0)