Ticket #5671 (closed bug: fixed)
ghc-7.2 vector code segfaults
The following program segfaults on x86_64 with vector-0.9
- with ghc-7.2.1 and -O
- with ghc-7.2.2 and -O
- with ghc-7.3.20111122 and -O
I does not segfault with ghc-7.0.4 or without -O.
It also segfaults on x86 if I change the number from 965 to 1934. I haven't thoroughly tested this, but these seem to be the smallest numbers each for which there is a segfault.
import qualified Data.Vector as U main :: IO () main = f (U.fromList (replicate 965 (((), ()), ()))) `seq` return () f x = g (fst (U.unzip x)) g x = U.zipWith (flip const) x (h (fst (U.unzip x))) h x = U.zipWith op y x where y = U.zipWith op x (U.init z) z = U.generate (n+1) (\ i -> x U.! (if i >= n then n - 1 else i)) n = U.length x op () () = ()
By looking at Core code a bit and comparing output from 7.0.4 and 7.2.2, I see reversed array indexing and bounds checking. So it looks like this might be related to bug #5658, but I'm not sure.