ForeignPtr leak in ghci

I have a program which creates an infinite list of Storable Vectors and then scans through the list until some condition has been met. When compiled, the program runs in constant space. When run in ghci, however, the program leaks memory.

I can reproduce the behavior with the following module, using both ghc-7.2.1 and ghc-7.4.0.20111219 on Mac OS X 10.7 x86_64. More precisely, I do not see a leak (using top) when the program is

• Compiled with ghc --make -O2 and run from the command-line
• Compiled with ghc --make -O0 and run from the command-line
• Compiled with ghc --make -O0, loaded into ghci and run with :main

But I do see a leak (top shows a growing memory usage) when the program is

• Loaded uncompiled into ghci and run with :main
• Compiled with ghc --make -O2 (or -O), loaded into ghci and run with :main.

module Main where

import System.IO.Unsafe
import Foreign.ForeignPtr
import Control.Exception

main = do
    let steps = infinite 256
    evaluate $ myLast steps

myLast :: [a] -> a
myLast [x] = x
myLast (x:xs) = myLast xs

infinite :: Int -> [ForeignPtr ()]
infinite n = let
    xs = makeVector n
    in xs `seq` (xs : infinite n)

makeVector :: Int -> ForeignPtr ()
makeVector n = unsafePerformIO $ mallocForeignPtrBytes n

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
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