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From: Steve Hill <sah@ukc.ac.uk>
To: glasgow-haskell-bugs@dcs.gla.ac.uk
Subject: Possible bug.
Date: Thu, 13 Aug 92 16:21:53 +0100

Report from Dr. Steve Hill, Computing Laboratory, University of Kent.
(sah@ukc.ac.uk)

--------
The following (rather silly) program causes a stack overflow (the B
stack I think):
----------------
module Main where

#include "GhcPrelude.h"

main :: Dialogue
main = print (final nums)

nums :: [Int]
nums = fromn 1

fromn :: Int -> [Int]
fromn n = n : fromn (n+1)

final :: [Int] -> Int
final (a:l) = seq (force a) (final l)

force :: Int -> Int
force a | a == a = a

seq :: Int -> Int -> Int
seq a b | a == a = b
-----------------

I would expect it to be able to run in constant space - I may be wrong.

This is the output:

beech.ukc.ac.uk% a.out
croaked in StackOverflow
beech.ukc.ac.uk% 

This is the output of a -v compilation:

beech.ukc.ac.uk% ghc -v Try.hs -cpp
The Glorious New Glasgow Haskell Compilation System, version 0.06
project label: `ghc'; setup label: `std'
using a `sun4' host to build a Haskell compiler to run on a
`sun4' host that will generate `C' code

Haskellised C pre-processor:
        echo '{-# LINE 1 "Try.hs"-}' > /tmp/ghc15040.cpp;
/proj/haskell/ghc-0.06/./driver/.././utils/scripts/hscpp  -v 
-D__HASKELL1__=2 -D__GLASGOW_HASKELL__ -I.
-I/proj/haskell/ghc-0.06/imports Try.hs >> /tmp/ghc15040.cpp
        0.1 real         0.0 user         0.0 sys  
hscpp:CPP invoked: /lib/cpp           -D__HASKELL1__=2
-D__GLASGOW_HASKELL__ -I. -I/proj/haskell/ghc-0.06/imports Try.hs

Haskell parser:
        /proj/haskell/ghc-0.06/./driver/.././parsers/hsp/hsp -v  -I.
-I/proj/haskell/ghc-0.06/imports /tmp/ghc15040.cpp > /tmp/ghc15040.hsp
Glasgow Haskell parser, version 0.06
Hash Table Contains 993 entries
        1.2 real         0.4 user         0.2 sys  

Haskell compiler:
        /proj/haskell/ghc-0.06/./driver/.././compiler/hsc <
/tmp/ghc15040.hsp  - -v > /tmp/ghc15040.hsc
Glasgow Haskell Compiler, version 0.06

       17.4 real         7.0 user         2.0 sys  

Pin on Haskell consistency info:
        echo 'static char ghc_hsc_ID[] = "@(#)hsc_comp Try.hs  
ver=1.0,";' >> /tmp/ghc15040.hsc
        0.1 real         0.0 user         0.0 sys  
extracting C (/tmp/ghc15040.hc) and interface (Try.hi) from /tmp/ghc15040.hsc
interface really going into: Main.hi

Comparing old and new .hi files:
        cmp -s /tmp/ghc15040.hi Main.hi || mv /tmp/ghc15040.hi Main.hi
        0.2 real         0.0 user         0.0 sys  

ANSI-C Haskell assembler:
        cc -v -S -DDO_RUNTIME_PROFILING -DDO_RUNTIME_TRACE_UPDATES -g
-DGC2s  -D__HASKELL1__=2 -D__GLASGOW_HASKELL__ -I.
-I/proj/haskell/ghc-0.06/imports /tmp/ghc15040.c -o /tmp/ghc15040.s
/lib/cpp -I. -I/proj/haskell/ghc-0.06/imports -undef -Dunix -Dsun
-Dsparc -DDO_RUNTIME_PROFILING -DDO_RUNTIME_TRACE_UPDATES -DGC2s
-D__HASKELL1__=2 -D__GLASGOW_HASKELL__ /tmp/ghc15040.c >/tmp/cpp.15067.0.i
/lib/ccom - -Xg </tmp/cpp.15067.0.i >/tmp/ghc15040.s
rm /tmp/cpp.15067.0.i
        2.6 real         1.6 user         0.5 sys  

Unix assembler:
        as  /tmp/ghc15040.s -o Try.o
        2.3 real         1.1 user         0.5 sys  

Linker:
        cc   Try.o
/proj/haskell/ghc-0.06/./driver/.././runtime/main/Preloads.sun4.o
-L/proj/haskell/ghc-0.06/./driver/.././runtime/objs-sun4
-L/proj/haskell/ghc-0.06/./driver/.././lib/objs-sun4 -lHS_2s -lHSrts_2s
       51.1 real        12.1 user         5.6 sys  
Checking consistency of: a.out

rm -f /tmp/ghc15040*
beech.ukc.ac.uk% 


Steve Hill.