[GHC] #9304: Floating point woes; Different behavior on Mac vs Linux

[GHC]

#9304: Floating point woes; Different behavior on Mac vs Linux
-------------------------------------+------------------------------------
        Reporter:  lerkok            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  high              |        Milestone:
       Component:  Compiler          |          Version:  7.8.3
      Resolution:                    |         Keywords:  floating point
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:  9276
        Blocking:                    |  Related Tickets:
-------------------------------------+------------------------------------

Comment (by lerkok):

 And here're the results for the original program:

 {{{
 [ubuntu-VirtualBox]~/precision/regular>cat main.hs
 x, y, r :: Double
 x = -4.4
 y = 2.4999999999999956
 r = x * y

 main :: IO ()
 main = print $ decodeFloat r
 [ubuntu-VirtualBox]~/precision/regular>rm main.hi; rm main.o; ghc main.hs
 -o main; ./main
 [1 of 1] Compiling Main             ( main.hs, main.o )
 Linking main ...
 (-6192449487634422,-49)
 [ubuntu-VirtualBox]~/precision/regular>rm main.hi; rm main.o; ghc main.hs
 -msse2 -o main; ./main
 [1 of 1] Compiling Main             ( main.hs, main.o )
 Linking main ...
 (-6192449487634422,-49)
 [ubuntu-VirtualBox]~/precision/regular>rm main.hi; rm main.o; ghc main.hs
 -fexcess-precision -o main; ./main
 [1 of 1] Compiling Main             ( main.hs, main.o )
 Linking main ...
 (-6192449487634422,-49)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9304#comment:22>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler