[GHC] #1176: Infinite loop when printing error message

[GHC]

#1176: Infinite loop when printing error message
------------------------------------------+---------------------------------
    Reporter:  Paul_Berry at alumni.hmc.edu  |       Owner:       
        Type:  bug                        |      Status:  new  
    Priority:  normal                     |   Milestone:       
   Component:  Compiler                   |     Version:  6.6  
    Severity:  normal                     |    Keywords:       
  Difficulty:  Unknown                    |    Testcase:       
Architecture:  x86                        |          Os:  Linux
------------------------------------------+---------------------------------
I am trying to compile a file that has a known compile error.  Ghc gets
 into an infinite loop trying to output the error message.

 Here's the session (captured using EMACS shell):

 {{{
 pberry at Dal:~/bridge_ghc_bug$ uname -a
 Linux Dal 2.6.18-3-686 #1 SMP Mon Dec 4 16:41:14 UTC 2006 i686 GNU/Linux
 pberry at Dal:~/bridge_ghc_bug$ gcc -v
 Using built-in specs.
 Target: i486-linux-gnu
 Configured with: ../src/configure -v --enable-
 languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-
 shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext
 --enable-threads=posix --enable-nls --program-suffix=-4.1 --enable-
 __cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr
 --with-tune=i686 --enable-checking=release i486-linux-gnu
 Thread model: posix
 gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
 pberry at Dal:~/bridge_ghc_bug$ ghc -v --make main.hs
 Glasgow Haskell Compiler, Version 6.6, for Haskell 98, compiled by GHC
 version 6.6
 Using package config file: /usr/lib/ghc-6.6/package.conf
 wired-in package base mapped to base-2.0
 wired-in package rts mapped to rts-1.0
 wired-in package haskell98 mapped to haskell98-1.0
 wired-in package template-haskell mapped to template-haskell-2.0
 Hsc static flags: -static
 *** Chasing dependencies:
 Chasing modules from: main.hs
 Stable obj: []
 Stable BCO: []
 compile: input file main.hs
 Created temporary directory: /tmp/ghc5182_0
 *** Checking old interface for main:Main:
 [1 of 1] Compiling Main             ( main.hs, main.o )
 *** Parser:
 *** Renamer/typechecker:

 main.hs:30:12:
     No instance for (Show Rank)
       arising from use of `show' at main.hs:30:12-19
     Possible fix: add an instance declaration for (Show Rank)
     In the first argument of `(~?=)', namely `show Ten'
     In the expression: (show Ten) ~?= "T"
     In the second argument of `($)', namely
         `[(show Two) ~?= "2", (show Three) ~?= "3", (show Four) ~?= "4",
       (show Five) ~?= "5", (show Six) ~?= "6", (show Seven) ~?= "7",
   (show Eight) ~?= "8", (show Nine) ~?= "9", (show Ten) ~?= "T",
 }}}

 At this point ghc goes into an (apparently) infinite loop outputting
 spaces.  When I interrupt it using Ctrl-C, it says:

 {{{
 *** Deleting temp files:
 Deleting: /tmp/ghc5182_0/ghc5182_0.s
 Warning: deleting non-existent /tmp/ghc5182_0/ghc5182_0.s
 *** Deleting temp dirs:
 Deleting: /tmp/ghc5182_0
 }}}

 Here's the file main.hs:

 {{{
 import System
 import Test.HUnit
 import Control.Monad
 import Data.List

 data Card = Card Rank Suit

 data Suit = Clubs | Diamonds | Hearts | Spades
     deriving (Enum, Eq)

 data Rank = Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten |
 Jack | Queen | King | Ace
     deriving (Enum, Ord, Eq)

 type Hand = [Card]

 hand :: String -> Hand
 hand = undefined

 main = undefined

 allTests = test $
            [show Two ~?= "2"
            ,show Three ~?= "3"
            ,show Four ~?= "4"
            ,show Five ~?= "5"
            ,show Six ~?= "6"
            ,show Seven ~?= "7"
            ,show Eight ~?= "8"
            ,show Nine ~?= "9"
            ,show Ten ~?= "T"
            ,hand "AK76543/32/AK2/3" ~?= exampleHand
            ]
     where exampleHand = []
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1176>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler