#5688: instance Read Integer/Rational/Double readsPrec out of memory and crash
due
to exponential notation
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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:
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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 "1000000000000000000e-1022" or
"0.00000000000000000000001e1023".
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!
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5688#comment:45>
GHC <http://www.haskell.org/ghc/>
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