id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,testcase,blockedby,blocking,related,differential
5671,ghc-7.2 vector code segfaults,kosmikus,,"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. ",bug,closed,normal,,Compiler,7.2.1,fixed,,hvr@…,Linux,x86_64 (amd64),Runtime crash,,,,,