#4867: ghci displays negative floats incorrectly (was: Incorrect result from
trig
functions)
-------------------------------+--------------------------------------------
Reporter: gwright | Owner: gwright
Type: bug | Status: new
Priority: high | Milestone: 7.0.2
Component: GHCi | Version: 7.0.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: MacOS X | Blocking:
Architecture: x86_64 (amd64) | Failure: Incorrect result at runtime
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Comment(by gwright):
Replying to [comment:42 altaic]:
> Agreed. I'm going to have another look at `Linker.c`.
>
> Optimizations appear to effect the bug quite a bit. The double '-'
happened for me with the "devel2" BuildFlavour. With "quickest"
BuildFlavour (no optimizations) I get the following output from GHCi:
>
> {{{
> Prelude> -1.0 :: Float
> -1.0
> Prelude> -1.0 :: Double
> 1.0000000000000253
> Prelude> (-1.0 :: Double) + (1.0 :: Double)
> 2.0000000000000253
> }}}
>
> So it's not just the failed negation of `x` in `showSignedFloat`; it
seems that other negations are failing as well, which is unsurprising.
Changes with optimization level point to a relocation issue. As the code
changes, the references to constant data move around, and the relocations
are different.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4867#comment:44>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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