program with GADTs segfaults when compiled with -prof and -auto-all

Consider the following modules Main.hs and M.hs:

module Main ( main )

where

import M

main :: IO ()
main = do let f = T [undefined, undefined]
          [a] <- c f (\t -> return [r (UR undefined) t])
          a

{-# OPTIONS_GHC -fglasgow-exts -fno-warn-incomplete-patterns #-}
module M ( R(..), U, r, T(..), c )

where

data T f where T :: [T f] -> T ()

data R t where
    UR  :: (T f -> ()) -> R (U f)
    R :: R () 

data U f

c ::  T f -> (T () -> a) -> a
c p@(T _) f = f p

r :: R (U f) -> T f -> IO ()
r a f = (fu a f) `seq` return ()

fu :: R (U f) -> T f -> ()
fu (UR f) = f

I get:

$ ghc --make -prof -auto-all Main
$ ./Main +RTS -p
Segmentation fault
$./Main
Segmentation fault

This is a boiled-down example taken from a large project. A couple of observations:

• I haven't been able to reproduce it using only one module
• The R constructor from type R is not used, but if removed, the segfault no longer happens
• If -auto-all is not used, the segfault does not happen
• I've been able to reproduce it both on linux and os x, using ghc 6.6.1

Trac metadata

Trac field	Value
Version	6.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	jcpetruzza@gmail.com
Operating system	Unknown
Architecture	Unknown