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Another attempt at haskell#364, haskell#509, haskell#602 with the following design choices: 1. On Windows systems, `Socket` becomes an `Either` over the existing "Posix" socket implemntation and a Windows equivalent using its `SOCKET` type. 2. On Posix systems, or without enabling the WinIO manager with `--io-manager=native`, the current behavior is unchanged. 3. *With* the WinIO manager, a greenfield implementation around the relevant syscalls is used, using IO Completion Ports (AKA "Overlapped IO") through GHC's `withOverlapped` For the places we need to mux between the two (`Network.Socket.Syscall`, `Network.Socket.Buffer`, etc.) the existing implementation is moved into a `Posix.hsc` and the WinIO one is defined in `WinIO.hsc`. There's certainly some cleanup and style improvements that could be done, but it passes all existing tests, and hopefully provides a clean separation between the existing code (which can stay unchanged) and direct use of Windows syscalls through `withOverlapped`.
mrkline
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Apr 5, 2026
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| -- On Windows with the WinIO (IOCP) I/O manager, GHC's withOverlappedEx | ||
| -- converts async exceptions (including the one thrown by timeout) into a | ||
| -- synchronous IOException via `throwWinErr ... 0` | ||
| -- ("The operation completed successfully"). | ||
| -- `timeout` does not recognise this IOException as | ||
| -- its own exception, so it escapes. |
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This is probably something worth discussing with GHC folks - the WinIO withOverlapped code eats async exceptions and turns them into IOExceptions, which breaks the assumptions of timeout and others I'm sure.
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Another attempt at #364, #509, #602 with the following design choices:
On Windows systems,
Socketbecomes anEitherover the existing "Posix" socket implemntation and a Windows equivalent using itsSOCKETtype.On Posix systems, or without enabling the WinIO manager with
--io-manager=native, the current behavior is unchanged.With the WinIO manager, a greenfield implementation around the relevant syscalls is used, using IO Completion Ports (AKA "Overlapped IO") through GHC's
withOverlappedFor the places we need to mux between the two
(
Network.Socket.Syscall,Network.Socket.Buffer, etc.) the existing implementation is moved into aPosix.hscand the WinIO one is defined inWinIO.hsc.There's certainly some cleanup and style improvements that could be done, but it passes all existing tests, and hopefully provides a clean separation between the existing code (which can stay unchanged) and direct use of Windows syscalls through
withOverlapped.