id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4845	internal error: threadStackUnderflow: not enough space for return values	igloo	simonmar	"With (the type-incorrect) `Foo.hs`:
{{{
module Foo where

import Data.Char
import System.Directory

main :: IO ()
main = do return ()
          return ()
          return ()
          return ()
          return ()
          return ()
          return ()
          return ()
          return ()
          let xs :: [(Int, Bool, Char, Char, Char)]
              xs = undefined
          mapM_ f xs
          return ()
          return ()

f :: (Int, Char, Char, Char) -> IO ()
f _ = return ()

f1 :: IO ()
f1 = return ()

f2 :: IO ()
f2 = return ()

f3 :: IO ()
f3 = return ()

f4 :: IO ()
f4 = return ()
}}}
I get:
{{{
$ ghci Foo.hs
GHCi, version 7.1.20101216: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
[1 of 1] Compiling Foo              ( Foo.hs, interpreted )
ghc-stage2: internal error: threadStackUnderflow: not enough space for return values
    (GHC version 7.1.20101216 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
}}}
"	bug	closed	highest	7.4.1	Runtime System	7.1	fixed			Unknown/Multiple	Unknown/Multiple	GHCi crash