unfoldrN, unfoldrNM and fromListN are dangerous #301
Description
Size argument supplied to all three functions unfoldrN, unfoldrNM and fromListN serves as hint for upper bound for the length of a vector. The problem is that regardless of how big a vector would have been, the supplied upper bound memory is allocated, even if it too big, which can result in an application being killed with an asynchronous exception HeapOverflow
fromListN.hs:
import qualified Data.Vector.Primitive as V
main = do
let xs = [1, 2, 3, 4, 5] :: [Int]
print $ V.fromListN (maxBound `div` 8) xs$ ghc fromListN.hs && ./fromListN
[1 of 1] Compiling Main ( fromListN.hs, fromListN.o )
fromListN: Out of memoryunfoldrN.hs
import qualified Data.Vector.Primitive as V
main = print (V.unfoldrN (maxBound `div` 8) (const Nothing) () :: V.Vector Int)$ ghc unfoldrN.hs && ./unfoldrN
[1 of 1] Compiling Main ( unfoldrN.hs, unfoldrN.o )
Linking unfoldrN ...
unfoldrN: Out of memoryunfoldrNM.hs
import Control.Exception
import qualified Data.Vector.Primitive as V
main = do
eRes <- try (V.unfoldrNM (maxBound `div` 8) (const $ pure Nothing) () :: IO (V.Vector Int))
print (eRes :: Either SomeException (V.Vector Int))$ stack exec -- ghc unfoldrNM.hs -O2 && ./unfoldrNM
[1 of 1] Compiling Main ( unfoldrNM.hs, unfoldrNM.o )
Linking unfoldrNM ...
Left heap overflow