Moduleghc-internal-9.1401.0Haskell2010

GHC.Internal.IO.SubSystem

The IoSubSystem control interface. These methods can be used to disambiguate between the two operations.

The API of this module is unstable and not meant to be consumed by the general public. If you absolutely must depend on it, make sure to use a tight upper bound, e.g., base < 4.X rather than base < 5, because the interface can change rapidly without much warning.

1 type
7 values

Packageghc-internal-9.1401.0
Exports8
LanguageHaskell2010
LicenceBSD-3-Clause
SourceSubSystem.hs

valuewithIoSubSystem :: (IoSubSystem -> IO a) -> IO a

valuewithIoSubSystem' :: (IoSubSystem -> a) -> a

valuewhenIoSubSystem :: IoSubSystem -> IO () -> IO ()

valueioSubSystem :: IoSubSystem

The IoSubSystem in use.

This is needed to optimize support for different IO Managers on Windows. GHC supports both the new WinIO manager as well as the old MIO (threaded), and ancient win32-legacy (non-threaded) ones. The WinIO manager uses native Win32 HANDLEs, whereas the other two use posix style FDs (via translation layers).

In many places in the I/O base library code, for correctness or performance on Windows, we have to take different code paths depending on which style of IO manager is in use. The IO manager is set on RTS startup (and the default choice can be overridden using RTS flags). On Windows this value is obtained by reading a global variable that is set by the RTS IOManager on startup.

On non-Windows systems this value is always IoPOSIX.

datadata IoSubSystem

The I/O SubSystem to use in the program.

Constructors

IoPOSIX
Use a POSIX I/O Sub-System
IoNative
Use platform native Sub-System. For unix OSes this is the same as IoPOSIX, but on Windows this means use the Windows native APIs for I/O, including IOCP and RIO.

Instances3Enum, Eq, Show

Enum IoSubSystemDefined in ghc-internal-9.1401.0 · GHC.Internal.IO.SubSystem
Eq IoSubSystemDefined in ghc-internal-9.1401.0 · GHC.Internal.IO.SubSystem
Show IoSubSystemDefined in ghc-internal-9.1401.0 · GHC.Internal.IO.SubSystem

valueconditional :: a -> a -> a

Conditionally execute an action depending on the configured I/O subsystem. On POSIX systems always execute the first action. On Windows execute the second action if WINIO as active, otherwise fall back to the first action.

value(<!>) :: a -> a -> a

Infix version of conditional. posix ! windows == conditional posix windows

valueisWindowsNativeIO :: Bool