good bug! -O or -O2 is irrelevant but it works if compiled with -fvia-C You (or someone else) should add it to http://hackage.haskell.org/trac/ghc Christian Brad Clow wrote:
I upgraded from GHC 6.6.1 to 6.8.1 and around that time I noticed that the output from an app I am working on changed. I have distilled the code down to the following example that produces different output depending on whether it is compiled with -O2 or not:
main = do let (T x) = read "T 3" print $ f x print $ g x
data T = T Int deriving (Read, Show)
f x = truncate $ 2000 / fromIntegral ((x * 25) + 10)
g :: Int -> Int g x = f x
Here is the transcript from a shell (example code is saved in test.hs):
$ ghc --make test.hs [1 of 1] Compiling Main ( test.hs, test.o ) Linking test ... $ ./test 23 23 $ rm test.hi test.o test $ ghc -O2 --make test.hs [1 of 1] Compiling Main ( test.hs, test.o ) Linking test ... $ ./test 23 24
It is a little disconcerting that -O2 changes the output. :-)
Regards brad