Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  closed  
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:  fixed |   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:  T7034 |  Blockedby:  
  Blocking:|Related:  
---+
Changes (by pcapriotti):

  * testcase:  => T7034


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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  closed  
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:  fixed |   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by igloo):

  * status:  merge => closed
  * resolution:  => fixed


Comment:

 Backported as:
 {{{
 commit 6cb84cb399c42a764a80b8b34cf67e9f0e9a3ed4
 Author: Ian Lynagh 
 Date:   Wed Mar 28 16:11:34 2012 +0100

 Backport the Read Integer/Double/Float change for "123e456"

 For the 7.4 branch, I've fixed this in a less pleaseant way, in order
 to avoid changing the library interfaces.
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Yet, I would vote to merge it into 7.4.2 (with or without bumping the base
 version).

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 I suppose, the change of "data Lexeme" in "Text.Read.Lex" is a more severe
 interface change.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 They go to the cvs-libraries list instead.
 http://www.haskell.org/pipermail/cvs-libraries/

 You can also look at them in http://darcs.haskell.org/packages/base.git/
 or https://github.com/ghc/packages-base

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Replying to [comment:58 simonmar]:
 > pasting the hash into Google is usually the best way :-)

 {{{
 Your search - 4d849e6729d25ac4561d597b203c2af8757e6275 - did not match any
 documents.
 }}}

 Which patches go to gmane.comp.lang.haskell.cvs.ghc? Why not these here?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by simonmar):

 Replying to [comment:56 igloo]:

 > We need to decide if we want to merge for 7.4.2. The arguments against
 doing so are:
 >  * Breaks the library interface policy, e.g. because the behaviour of
 `read "12e34" :: Integer` changes
 >  * Would mean we should bump base's version number to 4.6, which will
 mean lots of packages need updating.

 We could consider it a bug that `read "12e34"` worked before.  If we can
 reasonably claim that the other interface changes are in "internal"
 modules, then we could avoid bumping the base version (I don't know
 whether that's true or not though).

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by simonmar):

 Replying to [comment:57 maeder]:
 > I wonder, where I can look up these committed changes easily.

 pasting the hash into Google is usually the best way :-)

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 I wonder, where I can look up these committed changes easily.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  merge   
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by igloo):

  * status:  new => merge


Comment:

 Now fixed. This should be the complete patch list:
 {{{
 commit afcddc5ce033de84ab88e73657a2f753aaee785a
 Author: Ian Lynagh 
 Date:   Thu Mar 1 01:26:06 2012 +

 Refactor number lexing; part of #5688

 This doesn't change the behaviour yet, but I think it's a step in the
 right direction.

 commit 480b755a8397e75b6d58992664ab42c8ff0e1907
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:42:25 2012 +

 Rename lexNum test to lex001, and expand it

 commit 54ce8383cc610977b50f571782f35d1322283a79
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:57:54 2012 +

 Add a test for reading Doubles

 commit 35ff29d8fdf916c79a01103f0bb40ee6d3b50453
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:58:18 2012 +

 Change how NaN and Infinity are read by lex

 commit f3c88bed6c742982992ac4edc8b294c3445a157d
 Author: Ian Lynagh 
 Date:   Thu Mar 1 14:03:31 2012 +

 Add a readInteger001 test

 commit bed3d7937bea1619f7cf05af8babd8dd4385f348
 Author: Ian Lynagh 
 Date:   Thu Mar 1 14:05:36 2012 +

 Make "100e12" not parse as an Integer; part of #5688

 commit 4d849e6729d25ac4561d597b203c2af8757e6275
 Author: Ian Lynagh 
 Date:   Sun Mar 11 12:31:25 2012 +

 Avoid making huge Rational's when reading Double/Float; fixes #5688
 }}}

 We need to decide if we want to merge for 7.4.2. The arguments against
 doing so are:
  * Breaks the library interface policy, e.g. because the behaviour of
 `read "12e34" :: Integer` changes
  * Would mean we should bump base's version number to 4.6, which will mean
 lots of packages need updating.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by lelf):

 * cc: anton.nik@… (added)


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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 or shorter: `logBase 10 2 * fromIntegral (floatDigits 0 + snd (floatRange
 0))`

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 I think there was code to compute the exponent offset by the given
 fractional part and the maximal exponent for a floating point type can be
 computed by `floatRange` and `floatDigits`.

 {{{
 logBase 10 2 * fromIntegral (floatDigits 0) + logBase 10 2 * fromIntegral
 (snd (floatRange 0))
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Replying to [comment:49 igloo]:
 > `fracExp` in `libraries/base/Text/Read/Lex.hs` makes the `Rational`, and
 `fromRational` in `libraries/base/GHC/Float.lhs` converts the `Rational`
 to a `Double/Float`.

 Computing the possibly big Rational when reading is wrong in my eyes. The
 Lexeme must store the fraction and (optional) exponent separately! Only
 when converting to a floating point type you know how many digits in the
 exponent may make sense. (`Float.lhs` is incomprehensible for me, but it
 may do the right thing.)

 (An alternative is to set a fixed limit of 6 digits in the exponent,
 because more cannot be handled.)

 Going via Rational is bad for bigger floating point numbers. The right
 thing would be to compute the arguments for `encodeFloat` during
 conversion.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 http://en.wikipedia.org/wiki/Double-precision_floating-point_format shows
 the limits under "examples".

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 something like:

 {{{
 convert :: RealFloat a => Rational -> Integer -> a
 convert frac expo =
   let d = fromRational (frac * 10 ^^ expo)
   in if abs expo + abs (fromIntegral (length (show $ numerator frac)
   - length (show $ denominator frac)))
 < fromIntegral (uncurry max $ floatRange d) then d
 else case (frac < 0, expo < 0) of
  (True, True) -> -0
  (True, False) -> -1/0
  (False, True) -> 0
  (False, False) -> 1/0
 }}}

 floatRange returns 1024 for Double (that's the maximal size of the binary
 exponent).
 The size of the rational does almost not matter.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 Replying to [comment:47 maeder]:
 > The precise number given by the input string needs to be converted to
 the nearest representable number (by the round-to-nearest rule of IEEE 754
 floating-point arithmetic).

 Well, I think the only things we're required to accept are what "show" can
 produce, which won't have an exponent outside of `MIN_EXP .. MAX_EXP`.

 > If we assume that `fromRational` does this correctly, it is enough to
 roughly estimate when the value will definitely be +/- Infinity/Zero (in
 order to avoid computing an overly large Rational value causing this
 ticket).

 So what's the actual algorithm? Can it handle all cases correctly?

 > It remains to check, if `fromRational` does the right thing. I assume it
 replaces "%" by "/" and converts the two arguments from Integer to
 Double/Float first. (Where is the code for this?)

 `fracExp` in `libraries/base/Text/Read/Lex.hs` makes the `Rational`, and
 `fromRational` in `libraries/base/GHC/Float.lhs` converts the `Rational`
 to a `Double/Float`.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 ruby does seem to have a limit, although I'm not quite sure what it
 corresponds to:
 {{{
 $ ruby -e 'puts Float( "0." + "0"*20321 + "1e20321" )'
 9.88131291682493e-324
 $ ruby -e 'puts Float( "0." + "0"*20322 + "1e20322" )'
 -e:1: warning: Float 0.00... out of range
 0.0
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 The precise number given by the input string needs to be converted to the
 nearest representable number (by the round-to-nearest rule of IEEE 754
 floating-point arithmetic).

 If we assume that `fromRational` does this correctly, it is enough to
 roughly estimate when the value will definitely be +/- Infinity/Zero (in
 order to avoid computing an overly large Rational value causing this
 ticket).

 Roughly estimating makes failing inconsistent (at least not precise).

 It remains to check, if `fromRational` does the right thing. I assume it
 replaces "%" by "/" and converts the two arguments from Integer to
 Double/Float first. (Where is the code for this?)

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Replying to [comment:45 maeder]:
 > In this case, just checking the exponent against MAX_EXP and MIN_EXP is
 not enough. The length of the leading fractional needs to be considered,
 too, i.e. for extreme examples like "100e-1022" or
 "0.001e1023".

 This means checking the exponent size after normalizing the fraction
 (starting with 1).

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Replying to [comment:43 igloo]:
 > Replying to [comment:41 igloo]:
 > > but the second and third should break (I'm not sure what they should
 return. Whichever of Infinity, -Infinity, NaN and 0.0 best fits the
 implementation, I guess).
 >
 > Or perhaps if the exponent is `> FLT_MAX_EXP`, `< FLT_MIN_EXP`, `>
 DBL_MAX_EXP` or `< DBL_MIN_EXP` then read should fail?

 It seems the "e"-Notation is really (exponentially expanding) syntactic
 sugar for a plain decimal number (without e), i.e. the bits of the
 internal floats are not set directly.

 In this case, just checking the exponent against MAX_EXP and MIN_EXP is
 not enough. The length of the leading fractional needs to be considered,
 too, i.e. for extreme examples like "100e-1022" or
 "0.001e1023".

 I vote for that reading should not fail, but return +/- (sign preserving)
 Infinity or 0.0. (What case should return NaN? I think, no case.)

 Reading long integers as int does not fail, too!

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by gracjan):

 Anecdotal evidence from Ruby:

 {{{
 ~/devel$ ruby -e 'puts Float( (10 ^ 1000).to_s + "e-1000")'
 -e:1: warning: Float 994e-1000 out of range
 0.0

 ~/devel$ ruby -e 'puts Float( "0." + "0"*1000 + "1e1001" )'
 1.0
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 Replying to [comment:41 igloo]:
 ? but the second and third should break (I'm not sure what they should
 return. Whichever of Infinity, -Infinity, NaN and 0.0 best fits the
 implementation, I guess).

 Or perhaps if the exponent is `> FLT_MAX_EXP`, `< FLT_MIN_EXP`, `>
 DBL_MAX_EXP` or `< DBL_MIN_EXP` then read should fail?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 If we're merging, then below are the patches so far.

 Note that this means making a few visible changes, though:
  * The behaviour of `Read Integer` has changed
  * The `Text.Read.Lex.Lexeme` type has changed
  * There are a couple of new functions in `Text.Read.Lex`

 {{{
 commit afcddc5ce033de84ab88e73657a2f753aaee785a
 Author: Ian Lynagh 
 Date:   Thu Mar 1 01:26:06 2012 +

 Refactor number lexing; part of #5688

 This doesn't change the behaviour yet, but I think it's a step in the
 right direction.

 commit 480b755a8397e75b6d58992664ab42c8ff0e1907
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:42:25 2012 +

 Rename lexNum test to lex001, and expand it

 commit 54ce8383cc610977b50f571782f35d1322283a79
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:57:54 2012 +

 Add a test for reading Doubles

 commit 35ff29d8fdf916c79a01103f0bb40ee6d3b50453
 Author: Ian Lynagh 
 Date:   Thu Mar 1 13:58:18 2012 +

 Change how NaN and Infinity are read by lex

 commit f3c88bed6c742982992ac4edc8b294c3445a157d
 Author: Ian Lynagh 
 Date:   Thu Mar 1 14:03:31 2012 +

 Add a readInteger001 test

 commit bed3d7937bea1619f7cf05af8babd8dd4385f348
 Author: Ian Lynagh 
 Date:   Thu Mar 1 14:05:36 2012 +

 Make "100e12" not parse as an Integer; part of #5688
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 OK, in the `Read Double/Float` instances, we now have access to the
 integer part, the fractional part, and the exponent. The remaining part of
 the problem is how to convert these into a `Double/Float`.

 One approach that doesn't work well is converting the `x.y` part and then
 multiplying by `(10 ^ z)`. For example, given `4.2e-1` we would like to
 get this `Double`:
 {{{
 Prelude> 0.42 :: Double
 0.42
 }}}
 but we would actually get this `Double`:
 {{{
 Prelude> (4.2 :: Double) * (10 ** (-1))
 0.42004
 }}}

 Something else that works with the current code, is:
 {{{
 Prelude> read (show (10 ^ 1000) ++ "e-1000") :: Double
 1.0
 }}}
 despite this:
 {{{
 Prelude> read (show (10 ^ 1000)) :: Double
 Infinity
 }}}
 and similarly
 {{{
 Prelude> read ("0." ++ replicate 1000 '0' ++ "1e1001") :: Double
 1.0
 }}}
 despite:
 {{{
 Prelude> read ("0." ++ replicate 1000 '0' ++ "1") :: Double
 0.0
 }}}

 So my thoughts are that the first example should be supported (i.e. give
 us 0.42), but the second and third should break (I'm not sure what they
 should return. Whichever of Infinity, -Infinity, NaN and 0.0 best fits the
 implementation, I guess).

 What do people think?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  igloo   
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by simonpj):

  * owner:  => igloo


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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by iustin):

 Hi all,

 Any updates on this? Any way in which someone (not familiar with
 internals) could help?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Another advantage of removing `Rat` is, that code duplication to treat the
 `Rational` within `Rat` and `Exp`(i.e. the conversion to `Double`) is
 avoided.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 A fix should be easy. If the `Rat` constructor is not changed or removed
 it should be at least filled with the fractionals that are given without
 "e" (to allow some user code to go through, although with reduced
 functionality).

 The `Exp` constructor should store the fractional part as `Rational`
 rather than shifting it to an `Integer` an decreasing the exponent.

 A combination of the `Rat` and `Exp` constructores is then essential
 Daniels suggestion `"| RatExp Rational (Maybe Integer)"`.

 An advantage of removing `Rat` would be to better detect code that uses
 it.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by iustin):

 Replying to [comment:34 igloo]:
 > Replying to [comment:33 iustin]:
 > > Replying to [comment:31 igloo]:
 > > > This isn't a regression, so let's punt it to 7.6.
 > >
 > > It's not a regression, but IMHO it's a security bug.
 >
 > I don't think a DoS is as bad a problem as the phrase "security bug"
 implies.

 True. Can it be confirmed that a most this does is a crash of the runtime,
 with no other "bad" behaviours?

 >
 > > As such, it should be fixed even in lower versions, not only in a
 future one!
 >
 > We're not set up to be able to make releases on old branches.

 As I wrote in a previous comment, you don't need to make a full release,
 but for long-term distributions it would be very helpful if you release an
 "official" patch against older versions, that can be applied.

 > > I might overreact (sorry) but dragging the feet on such issues make it
 hard to promote the use of Haskell…
 >
 > Well, pragmatically speaking, currently we're past the feature freeze
 and into the RC phase (so ideally wouldn't be changing the definition of
 `Read Integer` etc), the release is already long overdue, and we don't
 have a good fix yet.

 Again, I don't propose to delay the release. What I'm interested in is to
 know for production environments that still run an older GHC release (6.12
 as that is in current Debian stable and Ubuntu LTS and 7.0/7.2), they can
 apply a "blessed" patch to their build systems in order to safeguard
 against this (once a good solution is found; I expect the fix to probably
 apply without issues to older versions too). That's all - the update of
 Milestone to 7.6 worried me that all older versions are left out in the
 cold.

 thanks again,
 iustin

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.4.2   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by simonmar):

  * milestone:  7.6.1 => 7.4.2


Comment:

 We don't have to wait until 7.6.1 to fix this, if the fix can be made with
 minimal disruption.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.6.1   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by igloo):

 Replying to [comment:33 iustin]:
 > Replying to [comment:31 igloo]:
 > > This isn't a regression, so let's punt it to 7.6.
 >
 > It's not a regression, but IMHO it's a security bug.

 I don't think a DoS is as bad a problem as the phrase "security bug"
 implies.

 > As such, it should be fixed even in lower versions, not only in a future
 one!

 We're not set up to be able to make releases on old branches.

 > I might overreact (sorry) but dragging the feet on such issues make it
 hard to promote the use of Haskell…

 Well, pragmatically speaking, currently we're past the feature freeze and
 into the RC phase (so ideally wouldn't be changing the definition of `Read
 Integer` etc), the release is already long overdue, and we don't have a
 good fix yet.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.6.1   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by iustin):

 Replying to [comment:31 igloo]:
 > This isn't a regression, so let's punt it to 7.6.

 It's not a regression, but IMHO it's a security bug. As such, it should be
 fixed even in lower versions, not only in a future one!

 I might overreact (sorry) but dragging the feet on such issues make it
 hard to promote the use of Haskell…

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.6.1   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+

Comment(by maeder):

 Looking at the patch, it seems that the old `Rat` constructor is unused
 and fractionals are treated as if "e0" had been appended, causing the
 (unfortunate) exponent change.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
---+
  Reporter:  gracjan   |  Owner:  
  Type:  bug   | Status:  new 
  Priority:  highest   |  Milestone:  7.6.1   
 Component:  libraries/base|Version:  6.12.3  
Resolution:|   Keywords:  
Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  Runtime crash | Difficulty:  Unknown 
  Testcase:|  Blockedby:  
  Blocking:|Related:  
---+
Changes (by igloo):

  * owner:  igloo =>
  * status:  patch => new
  * milestone:  7.4.1 => 7.6.1


Comment:

 This isn't a regression, so let's punt it to 7.6.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  igloo   
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 I think, eventually we want to reject "e-Notation" for rationals "at the
 prompt" (which is harder if already fractionals are represented via
 `Exp`).

 (And the read instance for rationals should accept the decimal point
 only.)

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  igloo   
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 I'm not happy, too. Representing all fractionals via `Exp` has some
 drawbacks. What does your patched `q` give for "420.0"?

 {{{
 Prelude> 4.200 * 10 ** 2
 420.0
 Prelude> 4200 * 10 ** (-5)
 420.06
 }}}

 I more liked Daniel's proposal: replacing the `Rat Rational` constructor
 with e.g. `RatExp Rational (Maybe Integer)`.

 Another point is, how such a literal is displayed in error messages by the
 patched ghc?

 {{{
 Prelude> 10.0 :: Integer
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  igloo   
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by simonmar):

 I was under the impression it wouldn't change anything, that looks
 suspicious to me.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  igloo   
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by igloo):

 I assume the patch we want is 0001-Added-new-Exp-constructor-to-
 Text.Read.Lex.Lexeme-so.patch?

 There were a few warnings, most notably in the "`a`" variables here:
 {{{
   valueFracExp a (Just fs) mExp -- 4.3[e2]
 = let (a,e) = fracExp (fromMaybe 0 mExp) a fs in Exp a e
 }}}
 which I assume was intended to be:
 {{{
   valueFracExp a (Just fs) mExp -- 4.3[e2]
 = let (a', e) = fracExp (fromMaybe 0 mExp) a fs
   in Exp a' e
 }}}

 `num008` then finds a number of differences, for example:

 {{{
 import Numeric

 main :: IO ()
 main = mapM_ (putStrLn . f) ["4.200e2", "1.8217369e0",
 "1.8217369e-300"]

 f :: String -> String
 f str = let d :: Double
 d = read str
 in str ++ replicate (15 - length str) ' ' ++ show d
 }}}

 Before the patch:
 {{{
 $ ghc --make q
 [1 of 1] Compiling Main ( q.hs, q.o )
 Linking q ...
 $ ./q
 4.200e2420.0
 1.8217369e01.8217369
 1.8217369e-300 1.8217369e-300
 }}}

 After the patch:
 {{{
 $ ghc --make q
 [1 of 1] Compiling Main ( q.hs, q.o )
 Linking q ...
 $ ./q
 4.200e2420.06
 1.8217369e01.82173689
 1.8217369e-300 1.82173687e-300
 }}}

 Are we happy with that?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  igloo   
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--
Changes (by simonmar):

  * owner:  => igloo


Comment:

 Ian, could you get this patch into 7.4.1 please?  (note this also closed
 #3897)

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--
Description changed by igloo:

Old description:

> {{{
>  GHCi, version 6.12.3: http://www.haskell.org/ghc/
>  Loading package ghc-prim ... linking ... done.
>  Loading package integer-gmp ... linking ... done.
>  Loading package base ... linking ... done.
>  Loading package ffi-1.0 ... linking ... done.
>  1200
>  Prelude> read "12e1" :: Integer
>  Segmentation fault
> }}}
>
> Sometimes it fails with Bus error.
>
> According to Haskell'98 and Haskell'00 Reports Integers should not parse
> exponential notation at all.
>
> http://www.haskell.org/onlinereport/haskell2010/haskellch2.html#x7-190002.5
>
> This is security issue in web frameworks as parsing HTTP headers, URLs,
> JSON and other may involve parsing integers.

New description:

 {{{
  GHCi, version 6.12.3: http://www.haskell.org/ghc/
  Loading package ghc-prim ... linking ... done.
  Loading package integer-gmp ... linking ... done.
  Loading package base ... linking ... done.
  Loading package ffi-1.0 ... linking ... done.
  1200
  Prelude> read "12e1" :: Integer
  Segmentation fault
 }}}

 Sometimes it fails with Bus error.

 According to Haskell'98 and Haskell'00 Reports Integers should not parse
 exponential notation at all.

 http://www.haskell.org/onlinereport/haskell2010/haskellch2.html#x7-190002.5

 This is security issue in web frameworks as parsing HTTP headers, URLs,
 JSON and other may involve parsing integers.

--

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 In this case the *son people may look at my code in:

 http://hackage.haskell.org/packages/archive/parsec-numbers/0.0.2/doc/html
 /Text-ParserCombinators-Parsec-Number.html

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by gracjan):

 To chime in: parsing Float and Double also kills programs because this
 goes through Rational.

 Text.JSON is self guilty. Here is the relevant snippet from json-0.5.
 File Text/JSON/String.hs:189

 {{{
exponent' n (c:cs)
 | c == 'e' || c == 'E' = (n*) <$> exp_num cs
exponent' n cs = setInput cs >> return n

exp_num  :: String -> GetJSON Rational
exp_num ('+':cs)  = exp_digs cs
exp_num ('-':cs)  = recip <$> exp_digs cs
exp_num cs= exp_digs cs

exp_digs :: String -> GetJSON Rational
exp_digs cs = case readDec cs of
[(a,ds)] -> do setInput ds
   return (fromIntegral ((10::Integer) ^ (a::Integer)))
_-> fail $ "Unable to parse JSON exponential: " ++ context
 cs

 }}}

 Same with aeson because of attoparsec: Data.Attoparsec.Text:

 {{{
 number :: Parser Number
 number = floaty $ \real frac fracDenom ->
  if frac == 0 && fracDenom == 0
  then I real
  else D (asDouble real frac fracDenom)

 ...
   let n = if fracDigits == 0
   then if power == 0
then fromIntegral real
else fromIntegral real * (10 ^^ power)
   else if power == 0
then f real fraction (10 ^ fracDigits)
else f real fraction (10 ^ fracDigits) * (10 ^^ power)
 }}}

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by iustin):

 Replying to [comment:21 maeder]:
 > Before you call read for Integer you can/should check if your string has
 at least one and only digits. Calling read is currently just as risky as
 calling "{{{^}}}" yourself.

 I'm sorry, unless I misunderstood what you meant, this is not an
 acceptable workaround except in trivial programs. This breaks any complex
 data structure that has Int/Integer/Rational fields, and it also breaks
 any libraries which assume that converting a string to an int is safe. For
 example, it also affects Text.JSON:

 {{{
 Prelude Text.JSON> decode "12e1" :: Result Int
 … hangs …
 }}}

 or the Aeson library:
 {{{
 Prelude Data.Aeson> decode "[12e1]" :: Maybe [Int]
 … hangs too …
 }}}

 So no, telling people that suddenly "read" is no longer safe and you have
 to do manual checks on its input depending on intended result type is not
 acceptable; this needs to be fixed at compiler level and also, IMHO, the
 fix backported to previous versions.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 Before you call read for Integer you can/should check if your string has
 at least one and only digits. Calling read is currently just as risky as
 calling "{{{^}}}" yourself.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--
Changes (by iustin):

 * cc: iustin@… (added)


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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by iustin):

 Replying to [comment:10 simonmar]:
 > I'm in favour of getting a fix for this into 7.4.1, given that it has
 security/DOS implications.

 Hi,

 Since this can be a security issue, I'd recommend also issuing patches
 that apply to older compilers, so that distributions can apply them/make a
 security advisory/etc. No need for a full release of (e.g.) ghc 6.12, but
 a "blessed" patch for it would be welcome. I'm picking on 6.12 mostly as
 Debian stable and Ubuntu Lucid (LTS) ship it.

 thanks!

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 The conversion from 123e10 to 1.23e12 in the message is also not nice.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by gracjan):

 I've created separate ticket for report change and source code compile:

 http://hackage.haskell.org/trac/ghc/ticket/5692

 Also to document 6.12.3 behavior:

 {{{
 GHCi, version 6.12.3: http://www.haskell.org/ghc/
 Prelude> read "123e10" :: Integer
 12300
 Prelude> read "123e10" :: Double
 1.23e12
 Prelude> read "123e10" :: Rational
 *** Exception: Prelude.read: no parse

 Prelude> 123e10 :: Integer

 :1:0:
 No instance for (Fractional Integer)
   arising from the literal `1.23e12' at :1:0-5
 Possible fix: add an instance declaration for (Fractional Integer)
 In the expression: 1.23e12 :: Integer
 In the definition of `it': it = 1.23e12 :: Integer
 Prelude> 123e10 :: Double
 1.23e12
 Prelude> 123e10 :: Rational
 12300 % 1
 }}}

 So source code compile of Integer and Rational is not compatible with Read
 instances.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 I think, read should behave like the haskell scanner and "10.01e10 ::
 Rational" should be rejected with "No instance for (Floating Rational)" as
 "10.01 :: Integer" is with:

 {{{
 Prelude> 10.10 :: Integer

 :1:1:
 No instance for (Fractional Integer)
   arising from the literal `10.1'
 ...
 }}}

 Another question is, if leading or trailing zeros should be preserved for
 messages.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 While read fails, 10.10 is a legal Rational Haskell value

 {{{
 *Main> 10.10 :: Rational
 101 % 10
 *Main> read "10.10" :: Rational
 *** Exception: Prelude.read: no parse
 }}}

 and

 {{{
 main = print (1E1000 :: Rational)
 }}}

 crashes the compiler as happens without type annotation currently.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 Ah, I believed "10.01" could be read as Rational, but I was wrong.

 I did not expect "10e10" to work with Integer and I'm surprised now that
 it does not work for Rational since I considered Rational to be a "more"
 than Integer.

 But maybe it is still a good idea to separate the fractional part from the
 exponent for proper "Fractional" numbers.

 http://www.haskell.org/onlinereport/haskell2010/haskellch6.html#x13-1360006.4.1
 does not clarify the connection of numeric literals to number types, but
 only reflects the bad
 connection of floats via Rational.

 So the report needs to be changed, too.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by gracjan):

 maeder, I do not understand your question. Lex.Lexeme is used to parse
 Integer, Float and Double only. Rationals are parsed as three lexemes:
 'Int' '%' 'Int'. They are in completely different place.

 Where do you need the conversion?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by maeder):

 >> How do you intent to store fractional numbers (like "10.01") without
 the
 >> Rat constructor?
 >
 > 10.01 = Exp 1001 (-2)

 can this be converted to a Rational, when e-Notation is no longer
 supported for rationals?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--

Comment(by gracjan):

 You are right, Float is base class for RealFrac so it will be better to
 use (**).

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
-+--
Reporter:  gracjan   |   Owner:  
Type:  bug   |  Status:  patch   
Priority:  highest   |   Milestone:  7.4.1   
   Component:  libraries/base| Version:  6.12.3  
Keywords:|  Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  | Failure:  Runtime crash   
  Difficulty:  Unknown   |Testcase:  
   Blockedby:|Blocking:  
 Related:|  
-+--
Changes (by simonmar):

  * priority:  normal => highest
  * difficulty:  => Unknown
  * milestone:  => 7.4.1


Comment:

 I'm in favour of getting a fix for this into 7.4.1, given that it has
 security/DOS implications.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-

Comment(by maeder):

 Is it not better to use "**" from the Floating class, rather than
 encodeFloat (from RealFloat) and this arbitrary "clampToInt" in
 convertFrac of your patch?

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-

Comment(by maeder):

 A fix should also support fixing #3897.

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-
Changes (by YitzGale):

 * cc: gale@… (added)


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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-

Comment(by FSalad):

 That was supposed to be "`^C`-resistant"

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-

Comment(by FSalad):

 No segfault on my system (Linux 3.1.1, GHC 7.2.1), just goes into a
 memory-consuming, ^C-resistant loop (presumably due to the huge size the
 representation of `read "12e1" :: Integer` would have)

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Re: [GHC] #5688: instance Read Integer/Rational/Double readsPrec out of memory and crash due to exponential notation (was: instance Read Integer readsPrec out of memory due to exponential notation)

[GHC]

#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash 
due
to exponential notation
--+-
 Reporter:  gracjan   |  Owner:  
 Type:  bug   | Status:  patch   
 Priority:  normal|  Component:  libraries/base  
  Version:  6.12.3|   Keywords:  
   Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash |   Testcase:  
Blockedby:|   Blocking:  
  Related:|  
--+-

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