[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))
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5688#comment:53>
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