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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Moduleghc-internal-9.1003.0Haskell2010

GHC.Internal.IO.Exception

IO-related Exception types and functions

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.

  • 14 types
  • 16 values
datadata Deadlock
#

There are no runnable threads, so the program is deadlocked. The Deadlock exception is raised in the main thread only.

Deadlock
Instances2Show, Exception
  • Show DeadlockDefined in ghc-internal-9.1003.0 · GHC.Internal.IO.Exception
  • Exception DeadlockDefined in ghc-internal-9.1003.0 · GHC.Internal.IO.Exception
datadata AsyncException
#

Asynchronous exceptions.

Constructors

  • StackOverflow

    The current thread's stack exceeded its limit. Since an exception has been raised, the thread's stack will certainly be below its limit again, but the programmer should take remedial action immediately.

  • HeapOverflow

    The program's heap is reaching its limit, and the program should take action to reduce the amount of live data it has. Notes:

    • It is undefined which thread receives this exception. GHC currently throws this to the same thread that receives UserInterrupt, but this may change in the future.

    • The GHC RTS currently can only recover from heap overflow if it detects that an explicit memory limit (set via RTS flags). has been exceeded. Currently, failure to allocate memory from the operating system results in immediate termination of the program.

  • ThreadKilled

    This exception is raised by another thread calling Control.Concurrent.killThread, or by the system if it needs to terminate the thread for some reason.

  • UserInterrupt

    This exception is raised by default in the main thread of the program when the user requests to terminate the program via the usual mechanism(s) (e.g. Control-C in the console).

Instances4Eq, Ord, Show, Exception
datadata ArrayException
#

Exceptions generated by array operations

Constructors

Instances4Eq, Ord, Show, Exception
datadata ExitCode
#

Defines the exit codes that a program can return.

Constructors

  • ExitSuccess

    indicates successful termination;

  • ExitFailure Int

    indicates program failure with an exit code. The exact interpretation of the code is operating-system dependent. In particular, some values may be prohibited (e.g. 0 on a POSIX-compliant system).

Instances7Eq, Ord, Read, Show, Generic, Exception, …
typetype IOError = IOException
#

The Haskell 2010 type for exceptions in the IO monad. Any I/O operation may raise an IOError instead of returning a result. For a more general type of exception, including also those that arise in pure code, see Control.Exception.Exception.

In Haskell 2010, this is an opaque type.

datadata IOException
#

Exceptions that occur in the IO monad. An IOException records a more specific error type, a descriptive string and maybe the handle that was used when the error was flagged.

Constructors

Instances3Eq, Show, Exception
datadata IOErrorType
#

An abstract type that contains a value for each variant of IOError.

AlreadyExistsNoSuchThingResourceBusyResourceExhaustedEOFIllegalOperationPermissionDeniedUserErrorUnsatisfiedConstraintsSystemErrorProtocolErrorOtherErrorInvalidArgumentInappropriateTypeHardwareFaultUnsupportedOperationTimeExpiredResourceVanishedInterrupted
Instances2Eq, Show
  • Eq IOErrorTypeDefined in ghc-internal-9.1003.0 · GHC.Internal.IO.Exception
  • Show IOErrorTypeDefined in ghc-internal-9.1003.0 · GHC.Internal.IO.Exception
valueuserError :: String -> IOError
#

Construct an IOError value with a string describing the error. The fail method of the IO instance of the Monad class raises a userError, thus:

instance Monad IO where
  ...
  fail s = ioError (userError s)