> Not sure if this counts as a bug or not, but I've got the following
> program:
>
>
> import GHC.Exts
> import Data.List
>
> wrapper_sum xs = ub_acc_sum xs 0#
> ub_acc_sum :: [Int] -> Int# -> Int
> ub_acc_sum [] v = I# v
> ub_acc_sum ((I# x):xs) v = ub_acc_sum xs (v +# x)
>
> main = do
> let l = take 10000000 [1,1..]
> seq (last l) $ return ()
> putStrLn "unboxed accum"
> putStrLn $ show $ wrapper_sum l
>
> When compiled with -O2 or -O1, and -prof and -auto-all, this
> runs out of
> stack space. Without optimisation, it's fine: likewise,
> without -prof it's
> fine, which seems reasonable: AFAICT, ub_acc_sum is tail-recursive.
While this behaviour is undesirable, I'm afraid it is entirely possible.
Compiling with profiling can, and very often does, affect the code that
gets generated - this is because in order to retain a correct cost
model, the optimiser must disable certain transformations.
Cheers,
Simon
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