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diff --git a/testsuite/tests/rts/overflow3.hs b/testsuite/tests/rts/overflow3.hs
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+++ b/testsuite/tests/rts/overflow3.hs
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+{-# LANGUAGE ForeignFunctionInterface #-}
+module Main where
+
+import Foreign
+
+-- Test allocate(), the easy way.
+data Cap = Cap
+foreign import ccall "rts_unsafeGetMyCapability" myCapability :: IO (Ptr Cap)
+foreign import ccall "allocate" allocate :: Ptr Cap -> Word -> IO (Ptr ())
+
+-- Number of words n such that n * sizeof(W_) exactly overflows a word
+-- (2^30 on a 32-bit system, 2^61 on a 64-bit system)
+overflowWordCount :: Word
+overflowWordCount = fromInteger $
+ (fromIntegral (maxBound :: Word) + 1) `div`
+ fromIntegral (sizeOf (undefined :: Word))
+
+main = do
+ cap <- myCapability
+ allocate cap (overflowWordCount + 1)