createPipe doesn't work on Windows

[TerrorJack]

Example program:

{-# LANGUAGE OverloadedStrings #-}

import qualified Data.ByteString as BS
import System.IO
import System.Process

main :: IO ()
main = do
  (h_read, h_write) <- createPipe
  let msg = "233"
  BS.hPut h_write msg
  hFlush h_write
  BS.hGet h_read (BS.length msg) >>= print

This prints "233" on Linux/macOS, but the program hangs indefinitely on Windows. Tested against ghc-8.10.1 which ships process-1.6.8.2, both on my Windows 10 laptop and on GitHub Actions.

[snoyberg]

I don't have easy access to a Windows machine right now to test this out, and honestly don't have any ideas on what might be causing this. @Mistuke any thoughts?

[Mistuke]

@snoyberg #182 fixes this. The code isn't broken it's just the buffer size is ridiculously low.

The write above blocks and is waiting for the read to drain it. but since everything is done on the same thread the program deadlocks.

[TerrorJack]

@snoyberg I just validated locally and @Mistuke's patch works, with threaded/non-threaded runtime. Would be nice to have a minor release for the bugfix. Thanks for the timely patch :D

[snoyberg]

Released on Hackage. Thanks @Mistuke!