[vector] #100: Data.Vector.Unboxed.Mutable.unsafeWrite fails on -O2

[vector]

#100: Data.Vector.Unboxed.Mutable.unsafeWrite fails on -O2
-------------------+--------------------------------------------------------
Reporter:  Y_Less  |       Owner:     
    Type:  defect  |      Status:  new
Priority:  major   |   Milestone:     
 Version:          |    Keywords:     
-------------------+--------------------------------------------------------
 As the title, but not always.  I have a script with a reduced test case
 that gives this result (when used with "inlinePerformIO", but also wrapped
 in "return"):

 {{{
 inlinePerformIO $ do
         let
                 len = r - prev
         -- Copy the name from the source to the destination.
         copyBytes (names `plusPtr` wName) (bsPtr `plusPtr` prev) len
         -- Copy the start offsets.
         putStrLn $ "hi" ++ show w0 ++ ": " ++ show wName ++ " = " ++ show
 wProt
         MVector.write nidx w0 wName
         MVector.write pidx w0 wProt
         return $ P6 3 (r + 1) (wName + len) wProt (w0 + 1) 0
 }}}

 The "MVector.write" line works correctly, but when replaced with
 "MVector.unsafeWrite", fails to write the data out - despite the fact that
 in this code the "putStrLn" is called correctly, the indexes are correct
 and so don't need to be checked, and as far as I can see the underlying
 implementation of "write" uses "unsafeWrite".

 I can provide a more complete example if required, as I suspect it will be
 given that "unsafeWrite" works fine in other places.

-- 
Ticket URL: <http://trac.haskell.org/vector/ticket/100>
vector <http://trac.haskell.org/vector>
Package vector