Simon Peyton Jones wrote:

I am therefore deeply reluctant to provide both GHC-for-mingw32 and GHC-for-cygwin. One build on Win32 is enough! We ended up with a mingw32 basis because it meant we could make GHC=20 completely self-contained -- no dependence on cygwin1.dll etc. This was *huge* step forward: GHC installs and runs with no problem on Windows now. I agree about it being a huge step forward. I do not think I would be in favour of undoing this and going back to having to install cygwin (in the right version) to get GHC to run. 1. GHC does not understand cygwin paths in the file names passed to it on the command line.

2. GHC on Win32 does not come with a Posix library. If we used a Cygwin basis, Posix would be easy because cygwin does all the hard work.

3. I/O on Win32 is *blocking*. A blocking input operation freezes all the other Haskell threads. I am a little but not hugely bothered by (1) and (2), as they can all be worked around in various ways. The real problem is (3), since it means that not just IO events but almost all events from the non-Haskell world cannot be waited on without bringing the Haskell world to a halt. Is it possible to do something about (3) without switching back to Cygwin?