[GHC] #1032: Test.QuickCheck.Batch overflow in length of tests

[GHC]

#1032: Test.QuickCheck.Batch overflow in length of tests
------------------------------------+---------------------------------------
    Reporter:  gwright at antiope.com  |       Owner:          
        Type:  bug                  |      Status:  new     
    Priority:  normal               |   Milestone:          
   Component:  Compiler             |     Version:  6.6     
    Severity:  normal               |    Keywords:          
  Difficulty:  Easy (1 hr)          |    Testcase:          
Architecture:  Multiple             |          Os:  Multiple
------------------------------------+---------------------------------------
This problem was originally reported as bug #1004.  There were
 actually two issues, which are now bug #1013 and this one.

 The following code fails (compiled and under ghci):

 {{{
 {-# OPTIONS_GHC -fglasgow-exts #-}
 --
 -- Checksum.hs, support for checksumming data.
 --


 --module Checksum (
 --        checksum
 --) where
 module Main where

 import Utils

 import Control.Exception
 import Data.Array
 import Data.Bits
 import Data.List
 import Data.Word
 import Test.QuickCheck
 import Test.QuickCheck.Batch


 crcTable :: Array Word8 Word16
 crcTable = listArray (0, 255)
     [ 0x0000, 0x5935, 0xB26A, 0xEB5F, 0x3DE1, 0x64D4, 0x8F8B, 0xD6BE,
       0x7BC2, 0x22F7, 0xC9A8, 0x909D, 0x4623, 0x1F16, 0xF449, 0xAD7C,
       0xF784, 0xAEB1, 0x45EE, 0x1CDB, 0xCA65, 0x9350, 0x780F, 0x213A,
       0x8C46, 0xD573, 0x3E2C, 0x6719, 0xB1A7, 0xE892, 0x03CD, 0x5AF8,
       0xB63D, 0xEF08, 0x0457, 0x5D62, 0x8BDC, 0xD2E9, 0x39B6, 0x6083,
       0xCDFF, 0x94CA, 0x7F95, 0x26A0, 0xF01E, 0xA92B, 0x4274, 0x1B41,
       0x41B9, 0x188C, 0xF3D3, 0xAAE6, 0x7C58, 0x256D, 0xCE32, 0x9707,
       0x3A7B, 0x634E, 0x8811, 0xD124, 0x079A, 0x5EAF, 0xB5F0, 0xECC5,
       0x354F, 0x6C7A, 0x8725, 0xDE10, 0x08AE, 0x519B, 0xBAC4, 0xE3F1,
       0x4E8D, 0x17B8, 0xFCE7, 0xA5D2, 0x736C, 0x2A59, 0xC106, 0x9833,
       0xC2CB, 0x9BFE, 0x70A1, 0x2994, 0xFF2A, 0xA61F, 0x4D40, 0x1475,
       0xB909, 0xE03C, 0x0B63, 0x5256, 0x84E8, 0xDDDD, 0x3682, 0x6FB7,
       0x8372, 0xDA47, 0x3118, 0x682D, 0xBE93, 0xE7A6, 0x0CF9, 0x55CC,
       0xF8B0, 0xA185, 0x4ADA, 0x13EF, 0xC551, 0x9C64, 0x773B, 0x2E0E,
       0x74F6, 0x2DC3, 0xC69C, 0x9FA9, 0x4917, 0x1022, 0xFB7D, 0xA248,
       0x0F34, 0x5601, 0xBD5E, 0xE46B, 0x32D5, 0x6BE0, 0x80BF, 0xD98A,
       0x6A9E, 0x33AB, 0xD8F4, 0x81C1, 0x577F, 0x0E4A, 0xE515, 0xBC20,
       0x115C, 0x4869, 0xA336, 0xFA03, 0x2CBD, 0x7588, 0x9ED7, 0xC7E2,
       0x9D1A, 0xC42F, 0x2F70, 0x7645, 0xA0FB, 0xF9CE, 0x1291, 0x4BA4,
       0xE6D8, 0xBFED, 0x54B2, 0x0D87, 0xDB39, 0x820C, 0x6953, 0x3066,
       0xDCA3, 0x8596, 0x6EC9, 0x37FC, 0xE142, 0xB877, 0x5328, 0x0A1D,
       0xA761, 0xFE54, 0x150B, 0x4C3E, 0x9A80, 0xC3B5, 0x28EA, 0x71DF,
       0x2B27, 0x7212, 0x994D, 0xC078, 0x16C6, 0x4FF3, 0xA4AC, 0xFD99,
       0x50E5, 0x09D0, 0xE28F, 0xBBBA, 0x6D04, 0x3431, 0xDF6E, 0x865B,
       0x5FD1, 0x06E4, 0xEDBB, 0xB48E, 0x6230, 0x3B05, 0xD05A, 0x896F,
       0x2413, 0x7D26, 0x9679, 0xCF4C, 0x19F2, 0x40C7, 0xAB98, 0xF2AD,
       0xA855, 0xF160, 0x1A3F, 0x430A, 0x95B4, 0xCC81, 0x27DE, 0x7EEB,
       0xD397, 0x8AA2, 0x61FD, 0x38C8, 0xEE76, 0xB743, 0x5C1C, 0x0529,
       0xE9EC, 0xB0D9, 0x5B86, 0x02B3, 0xD40D, 0x8D38, 0x6667, 0x3F52,
       0x922E, 0xCB1B, 0x2044, 0x7971, 0xAFCF, 0xF6FA, 0x1DA5, 0x4490,
       0x1E68, 0x475D, 0xAC02, 0xF537, 0x2389, 0x7ABC, 0x91E3, 0xC8D6,
       0x65AA, 0x3C9F, 0xD7C0, 0x8EF5, 0x584B, 0x017E, 0xEA21, 0xB314 ]


 -- | Compute our standard checksum
 --
 checksum :: [Word8] -> Word16
 checksum msg =
         let
                 update :: Word16 -> Word8 -> Word16
                 update reg byte = (reg `shiftL` 8) `xor`
                                   crcTable ! ((fromIntegral (reg `shiftR`
 8)) `xor` byte)
         in
                 foldl' update 0 msg



 -- | Tests
 --
 instance Arbitrary Word8 where
    arbitrary =
       do n <- choose ((fromIntegral (minBound :: Word8)) :: Int,
                       (fromIntegral (maxBound :: Word8)) :: Int)
          return (fromIntegral n)
    coarbitrary v = variant 0 . coarbitrary v


 prop_checksum xs = checksum (xs ++ splitWord (checksum xs)) == 0
                    where types = xs :: [Word8]

 testOpts = TestOptions {no_of_tests     = 1000,
                         length_of_tests = 3600,
                         debug_tests     = True}

 batch = do
   result <- run prop_checksum testOpts
   case result of
     TestOk       _    i _ -> putStrLn ("test ok: " ++ show i)
     TestExausted _    i _ -> putStrLn ("test exhausted: " ++ show i)
     TestFailed   strs i   -> putStrLn ("test failed: " ++ concat strs)
     TestAborted  ex       -> putStrLn ("test aborted: " ++ show ex)

 main = batch
 }}}

 it fails under ghci with

 {{{
 57:
 [61,48,20]
 58:
 [80,90,202,253,203,52,183]
 59:
 []
 60:
 [170,171,181,63,181,52,179,117]
 61:
 [56test aborted: <<loop>>
 *Main>
 }}}

 As noted by Thorkil (see #1004), the problem is in the length_of_tests
 field.
 This field is an Int, and is converted to microseconds by
 Test.QuickCheck.Batch.run.
 The conversion can overflow if length_of_tests is too large (a few
 thousand).

 That this error is not detected is a bug.  If the length_of_tests field is
 too
 large, ghc should do one of: 1) terminate with an error; 2) throw an
 exception;
 3) silently truncate to the maximum representable delay on the particular
 OS;
 4) wrap around, setting the delay to the specified delay modulo the
 maximum
 representable delay; or 5) do something better that someone else suggests.

 If anyone has a good suggest, I will be happy to work up a patch based on
 it.
 Otherwise, I'll pick one of 1) through 4).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1032>
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