{-# LANGUAGE CPP #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE UnliftedFFITypes #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE Unsafe #-}

{-# OPTIONS_HADDOCK not-home #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  GHC.Internal.Conc.Sync
-- Copyright   :  (c) The University of Glasgow, 1994-2002
-- License     :  see libraries/base/LICENSE
--
-- Maintainer  :  ghc-devs@haskell.org
-- Stability   :  internal
-- Portability :  non-portable (GHC extensions)
--
-- Basic concurrency stuff.
--
-----------------------------------------------------------------------------

-- No: #hide, because bits of this module are exposed by the stm package.
-- However, we don't want this module to be the home location for the
-- bits it exports, we'd rather have Control.Concurrent and the other
-- higher level modules be the home.  Hence:

-- #not-home
module GHC.Internal.Conc.Sync
        (
        -- * Threads
          ThreadId(..)
        , fromThreadId
        , showThreadId
        , myThreadId
        , killThread
        , throwTo
        , yield
        , labelThread
        , labelThreadByteArray#
        , mkWeakThreadId
        -- ** Queries
        , listThreads
        , threadLabel
        , ThreadStatus(..), BlockReason(..)
        , threadStatus
        , threadCapability

        -- * Forking and suchlike
        , forkIO
        , forkIOWithUnmask
        , forkOn
        , forkOnWithUnmask

        -- * Capabilities
        , numCapabilities
        , getNumCapabilities
        , setNumCapabilities
        , getNumProcessors

        -- * Sparks
        , numSparks
        , childHandler
        , par
        , pseq
        , runSparks

        -- * PrimMVar
        , newStablePtrPrimMVar, PrimMVar

        -- * Allocation counter and quota
        , setAllocationCounter
        , getAllocationCounter
        , enableAllocationLimit
        , disableAllocationLimit

        -- * TVars
        , STM(..)
        , atomically
        , retry
        , orElse
        , throwSTM
        , catchSTM
        , TVar(..)
        , newTVar
        , newTVarIO
        , readTVar
        , readTVarIO
        , writeTVar
        , unsafeIOToSTM

        -- * Miscellaneous
        , withMVar
        , modifyMVar_

        , setUncaughtExceptionHandler
        , getUncaughtExceptionHandler

        , reportError, reportStackOverflow, reportHeapOverflow

        , sharedCAF
        ) where

import GHC.Internal.Foreign.C.Types
import GHC.Internal.Foreign.C.String
import GHC.Internal.Foreign.Storable
import GHC.Internal.Foreign.StablePtr

import GHC.Internal.Base
import {-# SOURCE #-} GHC.Internal.IO.Handle ( hFlush )
import {-# SOURCE #-} GHC.Internal.IO.StdHandles ( stdout )
import GHC.Internal.Encoding.UTF8
import GHC.Internal.Int
import GHC.Internal.IO
import GHC.Internal.IO.Exception
import GHC.Internal.Exception
import GHC.Internal.IORef
import GHC.Internal.MVar
import GHC.Internal.Ptr
import GHC.Internal.Real         ( fromIntegral )
import GHC.Internal.Show         ( Show(..), showParen, showString )
import GHC.Internal.Weak
import GHC.Internal.Word

infixr 0 `par`, `pseq`

-----------------------------------------------------------------------------
-- 'ThreadId', 'par', and 'fork'
-----------------------------------------------------------------------------

data ThreadId = ThreadId ThreadId#
{- ^
A 'ThreadId' is an abstract type representing a handle to a thread.
'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
the 'Ord' instance implements an arbitrary total ordering over
'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
'ThreadId' to string form; showing a 'ThreadId' value is occasionally
useful when debugging or diagnosing the behaviour of a concurrent
program.

/Note/: in GHC, if you have a 'ThreadId', you essentially have
a pointer to the thread itself. This means the thread itself can\'t be
garbage collected until you drop the 'ThreadId'. This misfeature would
be difficult to correct while continuing to support 'threadStatus'.
-}

-- | Map a thread to an integer identifier which is unique within the
-- current process.
--
-- @since base-4.19.0.0
fromThreadId :: ThreadId -> Word64
fromThreadId :: ThreadId -> Word64
fromThreadId ThreadId
tid = CULLong -> Word64
forall a b. (Integral a, Num b) => a -> b
fromIntegral (CULLong -> Word64) -> CULLong -> Word64
forall a b. (a -> b) -> a -> b
$ ThreadId# -> CULLong
getThreadId (ThreadId -> ThreadId#
id2TSO ThreadId
tid)

-- | @since base-4.2.0.0
instance Show ThreadId where
   showsPrec :: Int -> ThreadId -> ShowS
showsPrec Int
d ThreadId
t = Bool -> ShowS -> ShowS
showParen (Int
d Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
11) (ShowS -> ShowS) -> ShowS -> ShowS
forall a b. (a -> b) -> a -> b
$
        String -> ShowS
showString String
"ThreadId " ShowS -> ShowS -> ShowS
forall b c a. (b -> c) -> (a -> b) -> a -> c
.
        Int -> Word64 -> ShowS
forall a. Show a => Int -> a -> ShowS
showsPrec Int
d (ThreadId -> Word64
fromThreadId ThreadId
t)

showThreadId :: ThreadId -> String
showThreadId :: ThreadId -> String
showThreadId = ThreadId -> String
forall a. Show a => a -> String
show

foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> CULLong

id2TSO :: ThreadId -> ThreadId#
id2TSO :: ThreadId -> ThreadId#
id2TSO (ThreadId ThreadId#
t) = ThreadId#
t

foreign import ccall unsafe "eq_thread" eq_thread :: ThreadId# -> ThreadId# -> CBool

foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> CInt
-- Returns -1, 0, 1

-- | @since base-4.2.0.0
instance Eq ThreadId where
  ThreadId ThreadId#
t1 == :: ThreadId -> ThreadId -> Bool
== ThreadId ThreadId#
t2 = ThreadId# -> ThreadId# -> CBool
eq_thread ThreadId#
t1 ThreadId#
t2 CBool -> CBool -> Bool
forall a. Eq a => a -> a -> Bool
/= CBool
0

-- | @since base-4.2.0.0
instance Ord ThreadId where
  compare :: ThreadId -> ThreadId -> Ordering
compare (ThreadId ThreadId#
t1) (ThreadId ThreadId#
t2) = case ThreadId# -> ThreadId# -> CInt
cmp_thread ThreadId#
t1 ThreadId#
t2 of
    -1 -> Ordering
LT
    CInt
0  -> Ordering
EQ
    CInt
_  -> Ordering
GT

-- | Every thread has an allocation counter that tracks how much
-- memory has been allocated by the thread.  The counter is
-- initialized to zero, and 'setAllocationCounter' sets the current
-- value.  The allocation counter counts *down*, so in the absence of
-- a call to 'setAllocationCounter' its value is the negation of the
-- number of bytes of memory allocated by the thread.
--
-- There are two things that you can do with this counter:
--
-- * Use it as a simple profiling mechanism, with
--   'getAllocationCounter'.
--
-- * Use it as a resource limit.  See 'enableAllocationLimit'.
--
-- Allocation accounting is accurate only to about 4Kbytes.
--
-- @since base-4.8.0.0
setAllocationCounter :: Int64 -> IO ()
setAllocationCounter :: Int64 -> IO ()
setAllocationCounter (I64# Int64#
i) = (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, () #)) -> IO ())
-> (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
  case Int64# -> State# RealWorld -> State# RealWorld
setThreadAllocationCounter# Int64#
i State# RealWorld
s of State# RealWorld
s' -> (# State# RealWorld
s', () #)

-- | Return the current value of the allocation counter for the
-- current thread.
--
-- @since base-4.8.0.0
getAllocationCounter :: IO Int64
getAllocationCounter :: IO Int64
getAllocationCounter = (State# RealWorld -> (# State# RealWorld, Int64 #)) -> IO Int64
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, Int64 #)) -> IO Int64)
-> (State# RealWorld -> (# State# RealWorld, Int64 #)) -> IO Int64
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
  case State# RealWorld -> (# State# RealWorld, Int64# #)
getThreadAllocationCounter# State# RealWorld
s of (# State# RealWorld
s', Int64#
ctr #) -> (# State# RealWorld
s', Int64# -> Int64
I64# Int64#
ctr #)

-- | Enables the allocation counter to be treated as a limit for the
-- current thread.  When the allocation limit is enabled, if the
-- allocation counter counts down below zero, the thread will be sent
-- the 'AllocationLimitExceeded' asynchronous exception.  When this
-- happens, the counter is reinitialised (by default
-- to 100K, but tunable with the @+RTS -xq@ option) so that it can handle
-- the exception and perform any necessary clean up.  If it exhausts
-- this additional allowance, another 'AllocationLimitExceeded' exception
-- is sent, and so forth.  Like other asynchronous exceptions, the
-- 'AllocationLimitExceeded' exception is deferred while the thread is inside
-- 'mask' or an exception handler in 'catch'.
--
-- Note that memory allocation is unrelated to /live memory/, also
-- known as /heap residency/.  A thread can allocate a large amount of
-- memory and retain anything between none and all of it.  It is
-- better to think of the allocation limit as a limit on
-- /CPU time/, rather than a limit on memory.
--
-- Compared to using timeouts, allocation limits don't count time
-- spent blocked or in foreign calls.
--
-- @since base-4.8.0.0
enableAllocationLimit :: IO ()
enableAllocationLimit :: IO ()
enableAllocationLimit = do
  ThreadId t <- IO ThreadId
myThreadId
  rts_enableThreadAllocationLimit t

-- | Disable allocation limit processing for the current thread.
--
-- @since base-4.8.0.0
disableAllocationLimit :: IO ()
disableAllocationLimit :: IO ()
disableAllocationLimit = do
  ThreadId t <- IO ThreadId
myThreadId
  rts_disableThreadAllocationLimit t

foreign import ccall unsafe "rts_enableThreadAllocationLimit"
  rts_enableThreadAllocationLimit :: ThreadId# -> IO ()

foreign import ccall unsafe "rts_disableThreadAllocationLimit"
  rts_disableThreadAllocationLimit :: ThreadId# -> IO ()

{- |
Creates a new thread to run the 'IO' computation passed as the
first argument, and returns the 'ThreadId' of the newly created
thread.

The new thread will be a lightweight, /unbound/ thread.  Foreign calls
made by this thread are not guaranteed to be made by any particular OS
thread; if you need foreign calls to be made by a particular OS
thread, then use 'Control.Concurrent.forkOS' instead.

The new thread inherits the /masked/ state of the parent (see
'GHC.Control.Exception.mask').

The newly created thread has an exception handler that discards the
exceptions 'BlockedIndefinitelyOnMVar', 'BlockedIndefinitelyOnSTM', and
'ThreadKilled', and passes all other exceptions to the uncaught
exception handler.

WARNING: Exceptions in the new thread will not be rethrown in the thread that
created it. This means that you might be completely unaware of the problem
if/when this happens.  You may want to use the
<https://hackage.haskell.org/package/async async> library instead.
-}
forkIO :: IO () -> IO ThreadId
forkIO :: IO () -> IO ThreadId
forkIO IO ()
action = (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, ThreadId #))
 -> IO ThreadId)
-> (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a b. (a -> b) -> a -> b
$ \ State# RealWorld
s ->
   case ((State# RealWorld -> (# State# RealWorld, () #))
-> State# RealWorld -> (# State# RealWorld, ThreadId# #)
forall a.
(State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld -> (# State# RealWorld, ThreadId# #)
fork# (IO () -> State# RealWorld -> (# State# RealWorld, () #)
forall a. IO a -> State# RealWorld -> (# State# RealWorld, a #)
unIO IO ()
action_plus) State# RealWorld
s) of (# State# RealWorld
s1, ThreadId#
tid #) -> (# State# RealWorld
s1, ThreadId# -> ThreadId
ThreadId ThreadId#
tid #)
 where
  -- We must use 'catch' rather than 'catchException' because the action
  -- could be bottom. #13330
  action_plus :: IO ()
action_plus = IO () -> (SomeException -> IO ()) -> IO ()
forall e a. Exception e => IO a -> (e -> IO a) -> IO a
catch IO ()
action SomeException -> IO ()
childHandler

-- | Like 'forkIO', but the child thread is passed a function that can
-- be used to unmask asynchronous exceptions.  This function is
-- typically used in the following way
--
-- >  ... mask_ $ forkIOWithUnmask $ \unmask ->
-- >                 catch (unmask ...) handler
--
-- so that the exception handler in the child thread is established
-- with asynchronous exceptions masked, meanwhile the main body of
-- the child thread is executed in the unmasked state.
--
-- Note that the unmask function passed to the child thread should
-- only be used in that thread; the behaviour is undefined if it is
-- invoked in a different thread.
--
-- @since base-4.4.0.0
forkIOWithUnmask :: ((forall a . IO a -> IO a) -> IO ()) -> IO ThreadId
forkIOWithUnmask :: ((forall a. IO a -> IO a) -> IO ()) -> IO ThreadId
forkIOWithUnmask (forall a. IO a -> IO a) -> IO ()
io = IO () -> IO ThreadId
forkIO ((forall a. IO a -> IO a) -> IO ()
io IO a -> IO a
forall a. IO a -> IO a
unsafeUnmask)

{- |
Like 'forkIO', but lets you specify on which capability the thread
should run.  Unlike a `forkIO` thread, a thread created by `forkOn`
will stay on the same capability for its entire lifetime (`forkIO`
threads can migrate between capabilities according to the scheduling
policy).  `forkOn` is useful for overriding the scheduling policy when
you know in advance how best to distribute the threads.

The `Int` argument specifies a /capability number/ (see
'getNumCapabilities').  Typically capabilities correspond to physical
processors, but the exact behaviour is implementation-dependent.  The
value passed to 'forkOn' is interpreted modulo the total number of
capabilities as returned by 'getNumCapabilities'.

GHC note: the number of capabilities is specified by the @+RTS -N@
option when the program is started.  Capabilities can be fixed to
actual processor cores with @+RTS -qa@ if the underlying operating
system supports that, although in practice this is usually unnecessary
(and may actually degrade performance in some cases - experimentation
is recommended).

@since base-4.4.0.0
-}
forkOn :: Int -> IO () -> IO ThreadId
forkOn :: Int -> IO () -> IO ThreadId
forkOn (I# Int#
cpu) IO ()
action = (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, ThreadId #))
 -> IO ThreadId)
-> (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a b. (a -> b) -> a -> b
$ \ State# RealWorld
s ->
   case (Int#
-> (State# RealWorld -> (# State# RealWorld, () #))
-> State# RealWorld
-> (# State# RealWorld, ThreadId# #)
forall a.
Int#
-> (State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld
-> (# State# RealWorld, ThreadId# #)
forkOn# Int#
cpu (IO () -> State# RealWorld -> (# State# RealWorld, () #)
forall a. IO a -> State# RealWorld -> (# State# RealWorld, a #)
unIO IO ()
action_plus) State# RealWorld
s) of (# State# RealWorld
s1, ThreadId#
tid #) -> (# State# RealWorld
s1, ThreadId# -> ThreadId
ThreadId ThreadId#
tid #)
 where
  -- We must use 'catch' rather than 'catchException' because the action
  -- could be bottom. #13330
  action_plus :: IO ()
action_plus = IO () -> (SomeException -> IO ()) -> IO ()
forall e a. Exception e => IO a -> (e -> IO a) -> IO a
catch IO ()
action SomeException -> IO ()
childHandler

-- | Like 'forkIOWithUnmask', but the child thread is pinned to the
-- given CPU, as with 'forkOn'.
--
-- @since base-4.4.0.0
forkOnWithUnmask :: Int -> ((forall a . IO a -> IO a) -> IO ()) -> IO ThreadId
forkOnWithUnmask :: Int -> ((forall a. IO a -> IO a) -> IO ()) -> IO ThreadId
forkOnWithUnmask Int
cpu (forall a. IO a -> IO a) -> IO ()
io = Int -> IO () -> IO ThreadId
forkOn Int
cpu ((forall a. IO a -> IO a) -> IO ()
io IO a -> IO a
forall a. IO a -> IO a
unsafeUnmask)

-- | the value passed to the @+RTS -N@ flag.  This is the number of
-- Haskell threads that can run truly simultaneously at any given
-- time, and is typically set to the number of physical processor cores on
-- the machine.
--
-- Strictly speaking it is better to use 'getNumCapabilities', because
-- the number of capabilities might vary at runtime.
--
numCapabilities :: Int
numCapabilities :: Int
numCapabilities = IO Int -> Int
forall a. IO a -> a
unsafePerformIO (IO Int -> Int) -> IO Int -> Int
forall a b. (a -> b) -> a -> b
$ IO Int
getNumCapabilities

{- |
Returns the number of Haskell threads that can run truly
simultaneously (on separate physical processors) at any given time.  To change
this value, use 'setNumCapabilities'.

@since base-4.4.0.0
-}
getNumCapabilities :: IO Int
getNumCapabilities :: IO Int
getNumCapabilities = do
   n <- Ptr CInt -> IO CInt
forall a. Storable a => Ptr a -> IO a
peek Ptr CInt
enabled_capabilities
   return (fromIntegral n)

{- |
Set the number of Haskell threads that can run truly simultaneously
(on separate physical processors) at any given time.  The number
passed to `forkOn` is interpreted modulo this value.  The initial
value is given by the @+RTS -N@ runtime flag.

This is also the number of threads that will participate in parallel
garbage collection.  It is strongly recommended that the number of
capabilities is not set larger than the number of physical processor
cores, and it may often be beneficial to leave one or more cores free
to avoid contention with other processes in the machine.

@since base-4.5.0.0
-}
setNumCapabilities :: Int -> IO ()
setNumCapabilities :: Int -> IO ()
setNumCapabilities Int
i
  | Int
i Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
0    = String -> IO ()
forall a. String -> IO a
failIO (String -> IO ()) -> String -> IO ()
forall a b. (a -> b) -> a -> b
$ String
"setNumCapabilities: Capability count ("String -> ShowS
forall a. [a] -> [a] -> [a]
++Int -> String
forall a. Show a => a -> String
show Int
iString -> ShowS
forall a. [a] -> [a] -> [a]
++String
") must be positive"
  | Bool
otherwise = CUInt -> IO ()
c_setNumCapabilities (Int -> CUInt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int
i)

foreign import ccall safe "setNumCapabilities"
  c_setNumCapabilities :: CUInt -> IO ()

-- | Returns the number of CPUs that the machine has
--
-- @since base-4.5.0.0
getNumProcessors :: IO Int
getNumProcessors :: IO Int
getNumProcessors = (CUInt -> Int) -> IO CUInt -> IO Int
forall a b. (a -> b) -> IO a -> IO b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap CUInt -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral IO CUInt
c_getNumberOfProcessors

foreign import ccall unsafe "getNumberOfProcessors"
  c_getNumberOfProcessors :: IO CUInt

-- | Returns the number of sparks currently in the local spark pool
numSparks :: IO Int
numSparks :: IO Int
numSparks = (State# RealWorld -> (# State# RealWorld, Int #)) -> IO Int
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, Int #)) -> IO Int)
-> (State# RealWorld -> (# State# RealWorld, Int #)) -> IO Int
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s -> case State# RealWorld -> (# State# RealWorld, Int# #)
forall d. State# d -> (# State# d, Int# #)
numSparks# State# RealWorld
s of (# State# RealWorld
s', Int#
n #) -> (# State# RealWorld
s', Int# -> Int
I# Int#
n #)

foreign import ccall "&enabled_capabilities" enabled_capabilities :: Ptr CInt

childHandler :: SomeException -> IO ()
childHandler :: SomeException -> IO ()
childHandler SomeException
err = IO () -> (SomeException -> IO ()) -> IO ()
forall e a. Exception e => IO a -> (e -> IO a) -> IO a
catch (SomeException -> IO ()
real_handler SomeException
err) SomeException -> IO ()
childHandler
  -- We must use catch here rather than catchException. If the
  -- raised exception throws an (imprecise) exception, then real_handler err
  -- will do so as well. If we use catchException here, then we could miss
  -- that exception.

real_handler :: SomeException -> IO ()
real_handler :: SomeException -> IO ()
real_handler SomeException
se
  | Just BlockedIndefinitelyOnMVar
BlockedIndefinitelyOnMVar <- SomeException -> Maybe BlockedIndefinitelyOnMVar
forall e. Exception e => SomeException -> Maybe e
fromException SomeException
se  =  () -> IO ()
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Just BlockedIndefinitelyOnSTM
BlockedIndefinitelyOnSTM  <- SomeException -> Maybe BlockedIndefinitelyOnSTM
forall e. Exception e => SomeException -> Maybe e
fromException SomeException
se  =  () -> IO ()
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Just AsyncException
ThreadKilled              <- SomeException -> Maybe AsyncException
forall e. Exception e => SomeException -> Maybe e
fromException SomeException
se  =  () -> IO ()
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Just AsyncException
StackOverflow             <- SomeException -> Maybe AsyncException
forall e. Exception e => SomeException -> Maybe e
fromException SomeException
se  =  IO ()
reportStackOverflow
  | Bool
otherwise                                           =  SomeException -> IO ()
reportError SomeException
se

{- | 'killThread' raises the 'ThreadKilled' exception in the given
thread (GHC only).

> killThread tid = throwTo tid ThreadKilled

-}
killThread :: ThreadId -> IO ()
killThread :: ThreadId -> IO ()
killThread ThreadId
tid = ThreadId -> AsyncException -> IO ()
forall e. Exception e => ThreadId -> e -> IO ()
throwTo ThreadId
tid AsyncException
ThreadKilled

{- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).

Exception delivery synchronizes between the source and target thread:
'throwTo' does not return until the exception has been raised in the
target thread. The calling thread can thus be certain that the target
thread has received the exception.  Exception delivery is also atomic
with respect to other exceptions. Atomicity is a useful property to have
when dealing with race conditions: e.g. if there are two threads that
can kill each other, it is guaranteed that only one of the threads
will get to kill the other.

Whatever work the target thread was doing when the exception was
raised is not lost: the computation is suspended until required by
another thread.

If the target thread is currently making a foreign call, then the
exception will not be raised (and hence 'throwTo' will not return)
until the call has completed.  This is the case regardless of whether
the call is inside a 'mask' or not.  However, in GHC a foreign call
can be annotated as @interruptible@, in which case a 'throwTo' will
cause the RTS to attempt to cause the call to return; see the GHC
documentation for more details.

Important note: the behaviour of 'throwTo' differs from that described in
the paper \"Asynchronous exceptions in Haskell\"
(<http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm>).
In the paper, 'throwTo' is non-blocking; but the library implementation adopts
a more synchronous design in which 'throwTo' does not return until the exception
is received by the target thread.  The trade-off is discussed in Section 9 of the paper.
Like any blocking operation, 'throwTo' is therefore interruptible (see Section 5.3 of
the paper).  Unlike other interruptible operations, however, 'throwTo'
is /always/ interruptible, even if it does not actually block.

There is no guarantee that the exception will be delivered promptly,
although the runtime will endeavour to ensure that arbitrary
delays don't occur.  In GHC, an exception can only be raised when a
thread reaches a /safe point/, where a safe point is where memory
allocation occurs.  Some loops do not perform any memory allocation
inside the loop and therefore cannot be interrupted by a 'throwTo'.

If the target of 'throwTo' is the calling thread, then the behaviour
is the same as 'GHC.Internal.Control.Exception.throwIO', except that the exception
is thrown as an asynchronous exception.  This means that if there is
an enclosing pure computation, which would be the case if the current
IO operation is inside 'unsafePerformIO' or 'unsafeInterleaveIO', that
computation is not permanently replaced by the exception, but is
suspended as if it had received an asynchronous exception.

Note that if 'throwTo' is called with the current thread as the
target, the exception will be thrown even if the thread is currently
inside 'mask' or 'uninterruptibleMask'.
  -}
throwTo :: Exception e => ThreadId -> e -> IO ()
throwTo :: forall e. Exception e => ThreadId -> e -> IO ()
throwTo (ThreadId ThreadId#
tid) e
ex = (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, () #)) -> IO ())
-> (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a b. (a -> b) -> a -> b
$ \ State# RealWorld
s ->
   case (ThreadId# -> SomeException -> State# RealWorld -> State# RealWorld
forall a. ThreadId# -> a -> State# RealWorld -> State# RealWorld
killThread# ThreadId#
tid (e -> SomeException
forall e. Exception e => e -> SomeException
toException e
ex) State# RealWorld
s) of State# RealWorld
s1 -> (# State# RealWorld
s1, () #)

-- | Returns the 'ThreadId' of the calling thread (GHC only).
myThreadId :: IO ThreadId
myThreadId :: IO ThreadId
myThreadId = (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, ThreadId #))
 -> IO ThreadId)
-> (State# RealWorld -> (# State# RealWorld, ThreadId #))
-> IO ThreadId
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
   case (State# RealWorld -> (# State# RealWorld, ThreadId# #)
myThreadId# State# RealWorld
s) of (# State# RealWorld
s1, ThreadId#
tid #) -> (# State# RealWorld
s1, ThreadId# -> ThreadId
ThreadId ThreadId#
tid #)


-- | The 'yield' action allows (forces, in a co-operative multitasking
-- implementation) a context-switch to any other currently runnable
-- threads (if any), and is occasionally useful when implementing
-- concurrency abstractions.
yield :: IO ()
yield :: IO ()
yield = (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, () #)) -> IO ())
-> (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
   case (State# RealWorld -> State# RealWorld
yield# State# RealWorld
s) of State# RealWorld
s1 -> (# State# RealWorld
s1, () #)

{- | 'labelThread' stores a string as identifier for this thread. This
identifier will be used in the debugging output to make distinction of
different threads easier (otherwise you only have the thread state object\'s
address in the heap). It also emits an event to the RTS eventlog.
-}
labelThread :: ThreadId -> String -> IO ()
labelThread :: ThreadId -> String -> IO ()
labelThread ThreadId
t String
str =
    ThreadId -> ByteArray# -> IO ()
labelThreadByteArray# ThreadId
t (String -> ByteArray#
utf8EncodeByteArray# String
str)

-- | 'labelThreadByteArray#' sets the label of a thread to the given UTF-8
--  encoded string contained in a `ByteArray#`.
--
--  @since base-4.18
labelThreadByteArray# :: ThreadId -> ByteArray# -> IO ()
labelThreadByteArray# :: ThreadId -> ByteArray# -> IO ()
labelThreadByteArray# (ThreadId ThreadId#
t) ByteArray#
str =
    (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, () #)) -> IO ())
-> (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s -> case ThreadId# -> ByteArray# -> State# RealWorld -> State# RealWorld
labelThread# ThreadId#
t ByteArray#
str State# RealWorld
s of State# RealWorld
s1 -> (# State# RealWorld
s1, () #)

--      Nota Bene: 'pseq' used to be 'seq'
--                 but 'seq' is now defined in GHC.Prim
--
-- "pseq" is defined a bit weirdly (see below)
--
-- The reason for the strange "lazy" call is that
-- it fools the compiler into thinking that pseq  and par are non-strict in
-- their second argument (even if it inlines pseq at the call site).
-- If it thinks pseq is strict in "y", then it often evaluates
-- "y" before "x", which is totally wrong.

{-# INLINE pseq  #-}
pseq :: a -> b -> b
pseq :: forall a b. a -> b -> b
pseq  a
x b
y = a
x a -> b -> b
forall a b. a -> b -> b
`seq` b -> b
forall a. a -> a
lazy b
y

{-# INLINE par  #-}
par :: a -> b -> b
par :: forall a b. a -> b -> b
par  a
x b
y = case (a -> Int#
forall a. a -> Int#
par# a
x) of { Int#
_ -> b -> b
forall a. a -> a
lazy b
y }

-- | Internal function used by the RTS to run sparks.
runSparks :: IO ()
runSparks :: IO ()
runSparks = (State# RealWorld -> (# State# RealWorld, () #)) -> IO ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO State# RealWorld -> (# State# RealWorld, () #)
forall {d}. State# d -> (# State# d, () #)
loop
  where loop :: State# d -> (# State# d, () #)
loop State# d
s = case State# d -> (# State# d, Int#, Any #)
forall d a. State# d -> (# State# d, Int#, a #)
getSpark# State# d
s of
                   (# State# d
s', Int#
n, Any
p #) ->
                      if Int# -> Bool
isTrue# (Int#
n Int# -> Int# -> Int#
==# Int#
0#)
                      then (# State# d
s', () #)
                      else Any
p Any -> (# State# d, () #) -> (# State# d, () #)
forall a b. a -> b -> b
`seq` State# d -> (# State# d, () #)
loop State# d
s'

-- | List the Haskell threads of the current process.
--
-- @since base-4.18
listThreads :: IO [ThreadId]
listThreads :: IO [ThreadId]
listThreads = (State# RealWorld -> (# State# RealWorld, [ThreadId] #))
-> IO [ThreadId]
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, [ThreadId] #))
 -> IO [ThreadId])
-> (State# RealWorld -> (# State# RealWorld, [ThreadId] #))
-> IO [ThreadId]
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
    case State# RealWorld -> (# State# RealWorld, Array# ThreadId# #)
listThreads# State# RealWorld
s of
      (# State# RealWorld
s', Array# ThreadId#
arr #) ->
        (# State# RealWorld
s', (ThreadId# -> ThreadId) -> Array# ThreadId# -> [ThreadId]
forall (a :: UnliftedType) b. (a -> b) -> Array# a -> [b]
mapListArrayUnlifted ThreadId# -> ThreadId
ThreadId Array# ThreadId#
arr #)

mapListArrayUnlifted :: forall (a :: TYPE UnliftedRep) b. (a -> b) -> Array# a -> [b]
mapListArrayUnlifted :: forall (a :: UnliftedType) b. (a -> b) -> Array# a -> [b]
mapListArrayUnlifted a -> b
f Array# a
arr = Int# -> [b]
go Int#
0#
  where
    sz :: Int#
sz = Array# a -> Int#
forall a. Array# a -> Int#
sizeofArray# Array# a
arr
    go :: Int# -> [b]
go Int#
i#
      | Int# -> Bool
isTrue# (Int#
i# Int# -> Int# -> Int#
==# Int#
sz) = []
      | Bool
otherwise = case Array# a -> Int# -> (# a #)
forall a. Array# a -> Int# -> (# a #)
indexArray# Array# a
arr Int#
i# of
                      (# a
x #) -> a -> b
f a
x b -> [b] -> [b]
forall a. a -> [a] -> [a]
: Int# -> [b]
go (Int#
i# Int# -> Int# -> Int#
+# Int#
1#)
{-# NOINLINE mapListArrayUnlifted #-}

data BlockReason
  = BlockedOnMVar
        -- ^blocked on 'MVar'
  {- possibly (see 'threadstatus' below):
  | BlockedOnMVarRead
        -- ^blocked on reading an empty 'MVar'
  -}
  | BlockedOnBlackHole
        -- ^blocked on a computation in progress by another thread
  | BlockedOnException
        -- ^blocked in 'throwTo'
  | BlockedOnSTM
        -- ^blocked in 'retry' in an STM transaction
  | BlockedOnForeignCall
        -- ^currently in a foreign call
  | BlockedOnOther
        -- ^blocked on some other resource.  Without @-threaded@,
        -- I\/O and 'Control.Concurrent.threadDelay' show up as
        -- 'BlockedOnOther', with @-threaded@ they show up as 'BlockedOnMVar'.
  deriving ( BlockReason -> BlockReason -> Bool
(BlockReason -> BlockReason -> Bool)
-> (BlockReason -> BlockReason -> Bool) -> Eq BlockReason
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: BlockReason -> BlockReason -> Bool
== :: BlockReason -> BlockReason -> Bool
$c/= :: BlockReason -> BlockReason -> Bool
/= :: BlockReason -> BlockReason -> Bool
Eq   -- ^ @since base-4.3.0.0
           , Eq BlockReason
Eq BlockReason =>
(BlockReason -> BlockReason -> Ordering)
-> (BlockReason -> BlockReason -> Bool)
-> (BlockReason -> BlockReason -> Bool)
-> (BlockReason -> BlockReason -> Bool)
-> (BlockReason -> BlockReason -> Bool)
-> (BlockReason -> BlockReason -> BlockReason)
-> (BlockReason -> BlockReason -> BlockReason)
-> Ord BlockReason
BlockReason -> BlockReason -> Bool
BlockReason -> BlockReason -> Ordering
BlockReason -> BlockReason -> BlockReason
forall a.
Eq a =>
(a -> a -> Ordering)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> a)
-> (a -> a -> a)
-> Ord a
$ccompare :: BlockReason -> BlockReason -> Ordering
compare :: BlockReason -> BlockReason -> Ordering
$c< :: BlockReason -> BlockReason -> Bool
< :: BlockReason -> BlockReason -> Bool
$c<= :: BlockReason -> BlockReason -> Bool
<= :: BlockReason -> BlockReason -> Bool
$c> :: BlockReason -> BlockReason -> Bool
> :: BlockReason -> BlockReason -> Bool
$c>= :: BlockReason -> BlockReason -> Bool
>= :: BlockReason -> BlockReason -> Bool
$cmax :: BlockReason -> BlockReason -> BlockReason
max :: BlockReason -> BlockReason -> BlockReason
$cmin :: BlockReason -> BlockReason -> BlockReason
min :: BlockReason -> BlockReason -> BlockReason
Ord  -- ^ @since base-4.3.0.0
           , Int -> BlockReason -> ShowS
[BlockReason] -> ShowS
BlockReason -> String
(Int -> BlockReason -> ShowS)
-> (BlockReason -> String)
-> ([BlockReason] -> ShowS)
-> Show BlockReason
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> BlockReason -> ShowS
showsPrec :: Int -> BlockReason -> ShowS
$cshow :: BlockReason -> String
show :: BlockReason -> String
$cshowList :: [BlockReason] -> ShowS
showList :: [BlockReason] -> ShowS
Show -- ^ @since base-4.3.0.0
           )

-- | The current status of a thread
data ThreadStatus
  = ThreadRunning
        -- ^the thread is currently runnable or running
  | ThreadFinished
        -- ^the thread has finished
  | ThreadBlocked  BlockReason
        -- ^the thread is blocked on some resource
  | ThreadDied
        -- ^the thread received an uncaught exception
  deriving ( ThreadStatus -> ThreadStatus -> Bool
(ThreadStatus -> ThreadStatus -> Bool)
-> (ThreadStatus -> ThreadStatus -> Bool) -> Eq ThreadStatus
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: ThreadStatus -> ThreadStatus -> Bool
== :: ThreadStatus -> ThreadStatus -> Bool
$c/= :: ThreadStatus -> ThreadStatus -> Bool
/= :: ThreadStatus -> ThreadStatus -> Bool
Eq   -- ^ @since base-4.3.0.0
           , Eq ThreadStatus
Eq ThreadStatus =>
(ThreadStatus -> ThreadStatus -> Ordering)
-> (ThreadStatus -> ThreadStatus -> Bool)
-> (ThreadStatus -> ThreadStatus -> Bool)
-> (ThreadStatus -> ThreadStatus -> Bool)
-> (ThreadStatus -> ThreadStatus -> Bool)
-> (ThreadStatus -> ThreadStatus -> ThreadStatus)
-> (ThreadStatus -> ThreadStatus -> ThreadStatus)
-> Ord ThreadStatus
ThreadStatus -> ThreadStatus -> Bool
ThreadStatus -> ThreadStatus -> Ordering
ThreadStatus -> ThreadStatus -> ThreadStatus
forall a.
Eq a =>
(a -> a -> Ordering)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> a)
-> (a -> a -> a)
-> Ord a
$ccompare :: ThreadStatus -> ThreadStatus -> Ordering
compare :: ThreadStatus -> ThreadStatus -> Ordering
$c< :: ThreadStatus -> ThreadStatus -> Bool
< :: ThreadStatus -> ThreadStatus -> Bool
$c<= :: ThreadStatus -> ThreadStatus -> Bool
<= :: ThreadStatus -> ThreadStatus -> Bool
$c> :: ThreadStatus -> ThreadStatus -> Bool
> :: ThreadStatus -> ThreadStatus -> Bool
$c>= :: ThreadStatus -> ThreadStatus -> Bool
>= :: ThreadStatus -> ThreadStatus -> Bool
$cmax :: ThreadStatus -> ThreadStatus -> ThreadStatus
max :: ThreadStatus -> ThreadStatus -> ThreadStatus
$cmin :: ThreadStatus -> ThreadStatus -> ThreadStatus
min :: ThreadStatus -> ThreadStatus -> ThreadStatus
Ord  -- ^ @since base-4.3.0.0
           , Int -> ThreadStatus -> ShowS
[ThreadStatus] -> ShowS
ThreadStatus -> String
(Int -> ThreadStatus -> ShowS)
-> (ThreadStatus -> String)
-> ([ThreadStatus] -> ShowS)
-> Show ThreadStatus
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> ThreadStatus -> ShowS
showsPrec :: Int -> ThreadStatus -> ShowS
$cshow :: ThreadStatus -> String
show :: ThreadStatus -> String
$cshowList :: [ThreadStatus] -> ShowS
showList :: [ThreadStatus] -> ShowS
Show -- ^ @since base-4.3.0.0
           )

-- | Query the current execution status of a thread.
threadStatus :: ThreadId -> IO ThreadStatus
threadStatus :: ThreadId -> IO ThreadStatus
threadStatus (ThreadId ThreadId#
t) = (State# RealWorld -> (# State# RealWorld, ThreadStatus #))
-> IO ThreadStatus
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, ThreadStatus #))
 -> IO ThreadStatus)
-> (State# RealWorld -> (# State# RealWorld, ThreadStatus #))
-> IO ThreadStatus
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
   case ThreadId#
-> State# RealWorld -> (# State# RealWorld, Int#, Int#, Int# #)
threadStatus# ThreadId#
t State# RealWorld
s of
    (# State# RealWorld
s', Int#
stat, Int#
_cap, Int#
_locked #) -> (# State# RealWorld
s', Int -> ThreadStatus
forall {a}. (Eq a, Num a) => a -> ThreadStatus
mk_stat (Int# -> Int
I# Int#
stat) #)
   where
        -- NB. keep these in sync with rts/include/rts/Constants.h
     mk_stat :: a -> ThreadStatus
mk_stat a
0  = ThreadStatus
ThreadRunning
     mk_stat a
1  = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnMVar
     mk_stat a
2  = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnBlackHole
     mk_stat a
6  = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnSTM
     mk_stat a
10 = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnForeignCall
     mk_stat a
11 = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnForeignCall
     mk_stat a
12 = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnException
     mk_stat a
14 = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnMVar -- possibly: BlockedOnMVarRead
     -- NB. these are hardcoded in rts/PrimOps.cmm
     mk_stat a
16 = ThreadStatus
ThreadFinished
     mk_stat a
17 = ThreadStatus
ThreadDied
     mk_stat a
_  = BlockReason -> ThreadStatus
ThreadBlocked BlockReason
BlockedOnOther

-- | Returns the number of the capability on which the thread is currently
-- running, and a boolean indicating whether the thread is locked to
-- that capability or not.  A thread is locked to a capability if it
-- was created with @forkOn@.
--
-- @since base-4.4.0.0
threadCapability :: ThreadId -> IO (Int, Bool)
threadCapability :: ThreadId -> IO (Int, Bool)
threadCapability (ThreadId ThreadId#
t) = (State# RealWorld -> (# State# RealWorld, (Int, Bool) #))
-> IO (Int, Bool)
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, (Int, Bool) #))
 -> IO (Int, Bool))
-> (State# RealWorld -> (# State# RealWorld, (Int, Bool) #))
-> IO (Int, Bool)
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
   case ThreadId#
-> State# RealWorld -> (# State# RealWorld, Int#, Int#, Int# #)
threadStatus# ThreadId#
t State# RealWorld
s of
     (# State# RealWorld
s', Int#
_, Int#
cap#, Int#
locked# #) -> (# State# RealWorld
s', (Int# -> Int
I# Int#
cap#, Int# -> Bool
isTrue# (Int#
locked# Int# -> Int# -> Int#
/=# Int#
0#)) #)

-- | Query the label of thread, returning 'Nothing' if the
-- thread's label has not been set.
--
-- @since base-4.18
threadLabel :: ThreadId -> IO (Maybe String)
threadLabel :: ThreadId -> IO (Maybe String)
threadLabel (ThreadId ThreadId#
t) = (State# RealWorld -> (# State# RealWorld, Maybe String #))
-> IO (Maybe String)
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, Maybe String #))
 -> IO (Maybe String))
-> (State# RealWorld -> (# State# RealWorld, Maybe String #))
-> IO (Maybe String)
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
    case ThreadId#
-> State# RealWorld -> (# State# RealWorld, Int#, ByteArray# #)
threadLabel# ThreadId#
t State# RealWorld
s of
      (# State# RealWorld
s', Int#
1#, ByteArray#
lbl #) ->
          let lbl' :: String
lbl' = ByteArray# -> String
utf8DecodeByteArray# ByteArray#
lbl
          in (# State# RealWorld
s', String -> Maybe String
forall a. a -> Maybe a
Just String
lbl' #)
      (# State# RealWorld
s', Int#
0#, ByteArray#
_ #) -> (# State# RealWorld
s', Maybe String
forall a. Maybe a
Nothing #)
      (# State# RealWorld, Int#, ByteArray# #)
_ -> String -> (# State# RealWorld, Maybe String #)
forall a. HasCallStack => String -> a
error String
"threadLabel: impossible"

-- | Make a weak pointer to a 'ThreadId'.  It can be important to do
-- this if you want to hold a reference to a 'ThreadId' while still
-- allowing the thread to receive the @BlockedIndefinitely@ family of
-- exceptions (e.g. 'BlockedIndefinitelyOnMVar').  Holding a normal
-- 'ThreadId' reference will prevent the delivery of
-- @BlockedIndefinitely@ exceptions because the reference could be
-- used as the target of 'throwTo' at any time, which would unblock
-- the thread.
--
-- Holding a @Weak ThreadId@, on the other hand, will not prevent the
-- thread from receiving @BlockedIndefinitely@ exceptions.  It is
-- still possible to throw an exception to a @Weak ThreadId@, but the
-- caller must use @deRefWeak@ first to determine whether the thread
-- still exists.
--
-- @since base-4.6.0.0
mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
mkWeakThreadId t :: ThreadId
t@(ThreadId ThreadId#
t#) = (State# RealWorld -> (# State# RealWorld, Weak ThreadId #))
-> IO (Weak ThreadId)
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, Weak ThreadId #))
 -> IO (Weak ThreadId))
-> (State# RealWorld -> (# State# RealWorld, Weak ThreadId #))
-> IO (Weak ThreadId)
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s ->
   case ThreadId#
-> ThreadId
-> State# RealWorld
-> (# State# RealWorld, Weak# ThreadId #)
forall a b.
a -> b -> State# RealWorld -> (# State# RealWorld, Weak# b #)
mkWeakNoFinalizer# ThreadId#
t# ThreadId
t State# RealWorld
s of
      (# State# RealWorld
s1, Weak# ThreadId
w #) -> (# State# RealWorld
s1, Weak# ThreadId -> Weak ThreadId
forall v. Weak# v -> Weak v
Weak Weak# ThreadId
w #)


-----------------------------------------------------------------------------
-- Transactional heap operations
-----------------------------------------------------------------------------

-- TVars are shared memory locations which support atomic memory
-- transactions.

-- |A monad supporting atomic memory transactions.
newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))

unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
unSTM :: forall a. STM a -> State# RealWorld -> (# State# RealWorld, a #)
unSTM (STM State# RealWorld -> (# State# RealWorld, a #)
a) = State# RealWorld -> (# State# RealWorld, a #)
a

-- | @since base-4.3.0.0
instance  Functor STM where
   fmap :: forall a b. (a -> b) -> STM a -> STM b
fmap a -> b
f STM a
x = STM a
x STM a -> (a -> STM b) -> STM b
forall a b. STM a -> (a -> STM b) -> STM b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= (b -> STM b
forall a. a -> STM a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (b -> STM b) -> (a -> b) -> a -> STM b
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> b
f)

-- | @since base-4.8.0.0
instance Applicative STM where
  {-# INLINE pure #-}
  {-# INLINE (*>) #-}
  {-# INLINE liftA2 #-}
  pure :: forall a. a -> STM a
pure a
x = a -> STM a
forall a. a -> STM a
returnSTM a
x
  <*> :: forall a b. STM (a -> b) -> STM a -> STM b
(<*>) = STM (a -> b) -> STM a -> STM b
forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
ap
  liftA2 :: forall a b c. (a -> b -> c) -> STM a -> STM b -> STM c
liftA2 = (a -> b -> c) -> STM a -> STM b -> STM c
forall (m :: * -> *) a1 a2 r.
Monad m =>
(a1 -> a2 -> r) -> m a1 -> m a2 -> m r
liftM2
  STM a
m *> :: forall a b. STM a -> STM b -> STM b
*> STM b
k = STM a -> STM b -> STM b
forall a b. STM a -> STM b -> STM b
thenSTM STM a
m STM b
k

-- | @since base-4.3.0.0
instance  Monad STM  where
    {-# INLINE (>>=)  #-}
    STM a
m >>= :: forall a b. STM a -> (a -> STM b) -> STM b
>>= a -> STM b
k     = STM a -> (a -> STM b) -> STM b
forall a b. STM a -> (a -> STM b) -> STM b
bindSTM STM a
m a -> STM b
k
    >> :: forall a b. STM a -> STM b -> STM b
(>>) = STM a -> STM b -> STM b
forall a b. STM a -> STM b -> STM b
forall (f :: * -> *) a b. Applicative f => f a -> f b -> f b
(*>)

-- | @since base-4.17.0.0
instance Semigroup a => Semigroup (STM a) where
    <> :: STM a -> STM a -> STM a
(<>) = (a -> a -> a) -> STM a -> STM a -> STM a
forall a b c. (a -> b -> c) -> STM a -> STM b -> STM c
forall (f :: * -> *) a b c.
Applicative f =>
(a -> b -> c) -> f a -> f b -> f c
liftA2 a -> a -> a
forall a. Semigroup a => a -> a -> a
(<>)

-- | @since base-4.17.0.0
instance Monoid a => Monoid (STM a) where
    mempty :: STM a
mempty = a -> STM a
forall a. a -> STM a
forall (f :: * -> *) a. Applicative f => a -> f a
pure a
forall a. Monoid a => a
mempty

bindSTM :: STM a -> (a -> STM b) -> STM b
bindSTM :: forall a b. STM a -> (a -> STM b) -> STM b
bindSTM (STM State# RealWorld -> (# State# RealWorld, a #)
m) a -> STM b
k = (State# RealWorld -> (# State# RealWorld, b #)) -> STM b
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ( \State# RealWorld
s ->
  case State# RealWorld -> (# State# RealWorld, a #)
m State# RealWorld
s of
    (# State# RealWorld
new_s, a
a #) -> STM b -> State# RealWorld -> (# State# RealWorld, b #)
forall a. STM a -> State# RealWorld -> (# State# RealWorld, a #)
unSTM (a -> STM b
k a
a) State# RealWorld
new_s
  )

thenSTM :: STM a -> STM b -> STM b
thenSTM :: forall a b. STM a -> STM b -> STM b
thenSTM (STM State# RealWorld -> (# State# RealWorld, a #)
m) STM b
k = (State# RealWorld -> (# State# RealWorld, b #)) -> STM b
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ( \State# RealWorld
s ->
  case State# RealWorld -> (# State# RealWorld, a #)
m State# RealWorld
s of
    (# State# RealWorld
new_s, a
_ #) -> STM b -> State# RealWorld -> (# State# RealWorld, b #)
forall a. STM a -> State# RealWorld -> (# State# RealWorld, a #)
unSTM STM b
k State# RealWorld
new_s
  )

returnSTM :: a -> STM a
returnSTM :: forall a. a -> STM a
returnSTM a
x = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM (\State# RealWorld
s -> (# State# RealWorld
s, a
x #))

-- | Takes the first non-'retry'ing 'STM' action.
--
-- @since base-4.8.0.0
instance Alternative STM where
  empty :: forall a. STM a
empty = STM a
forall a. STM a
retry
  <|> :: forall a. STM a -> STM a -> STM a
(<|>) = STM a -> STM a -> STM a
forall a. STM a -> STM a -> STM a
orElse

-- | Takes the first non-'retry'ing 'STM' action.
--
-- @since base-4.3.0.0
instance MonadPlus STM

-- | Unsafely performs IO in the STM monad.  Beware: this is a highly
-- dangerous thing to do.
--
--   * The STM implementation will often run transactions multiple
--     times, so you need to be prepared for this if your IO has any
--     side effects.
--
--   * The STM implementation will abort transactions that are known to
--     be invalid and need to be restarted.  This may happen in the middle
--     of `unsafeIOToSTM`, so make sure you don't acquire any resources
--     that need releasing (exception handlers are ignored when aborting
--     the transaction).  That includes doing any IO using Handles, for
--     example.  Getting this wrong will probably lead to random deadlocks.
--
--   * The transaction may have seen an inconsistent view of memory when
--     the IO runs.  Invariants that you expect to be true throughout
--     your program may not be true inside a transaction, due to the
--     way transactions are implemented.  Normally this wouldn't be visible
--     to the programmer, but using `unsafeIOToSTM` can expose it.
--
unsafeIOToSTM :: IO a -> STM a
unsafeIOToSTM :: forall a. IO a -> STM a
unsafeIOToSTM (IO State# RealWorld -> (# State# RealWorld, a #)
m) = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM State# RealWorld -> (# State# RealWorld, a #)
m

-- | Perform a series of STM actions atomically.
--
-- Using 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'
-- subverts some of guarantees that STM provides. It makes it possible to
-- run a transaction inside of another transaction, depending on when the
-- thunk is evaluated. If a nested transaction is attempted, an exception
-- is thrown by the runtime. It is possible to safely use 'atomically' inside
-- 'unsafePerformIO' or 'unsafeInterleaveIO', but the typechecker does not
-- rule out programs that may attempt nested transactions, meaning that
-- the programmer must take special care to prevent these.
--
-- However, there are functions for creating transactional variables that
-- can always be safely called in 'unsafePerformIO'. See: 'newTVarIO',
-- 'Control.Concurrent.STM.TChan.newTChanIO',
-- 'Control.Concurrent.STM.TChan.newBroadcastTChanIO',
-- 'Control.Concurrent.STM.TQueue.newTQueueIO',
-- 'Control.Concurrent.STM.TBQueue.newTBQueueIO', and
-- 'Control.Concurrent.STM.TMVar.newTMVarIO'.
--
-- Using 'unsafePerformIO' inside of 'atomically' is also dangerous but for
-- different reasons. See 'unsafeIOToSTM' for more on this.

atomically :: STM a -> IO a
atomically :: forall a. STM a -> IO a
atomically (STM State# RealWorld -> (# State# RealWorld, a #)
m) = (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO (\State# RealWorld
s -> ((State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld -> (# State# RealWorld, a #)
forall a.
(State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld -> (# State# RealWorld, a #)
atomically# State# RealWorld -> (# State# RealWorld, a #)
m) State# RealWorld
s )

-- | Retry execution of the current memory transaction because it has seen
-- values in 'TVar's which mean that it should not continue (e.g. the 'TVar's
-- represent a shared buffer that is now empty).  The implementation may
-- block the thread until one of the 'TVar's that it has read from has been
-- updated. (GHC only)
retry :: STM a
retry :: forall a. STM a
retry = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, a #)) -> STM a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s# -> State# RealWorld -> (# State# RealWorld, a #)
forall a. State# RealWorld -> (# State# RealWorld, a #)
retry# State# RealWorld
s#

-- | Compose two alternative STM actions (GHC only).
--
-- If the first action completes without retrying then it forms the result of
-- the 'orElse'. Otherwise, if the first action retries, then the second action
-- is tried in its place. If both actions retry then the 'orElse' as a whole
-- retries.
orElse :: STM a -> STM a -> STM a
orElse :: forall a. STM a -> STM a -> STM a
orElse (STM State# RealWorld -> (# State# RealWorld, a #)
m) STM a
e = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, a #)) -> STM a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s -> (State# RealWorld -> (# State# RealWorld, a #))
-> (State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld
-> (# State# RealWorld, a #)
forall a.
(State# RealWorld -> (# State# RealWorld, a #))
-> (State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld
-> (# State# RealWorld, a #)
catchRetry# State# RealWorld -> (# State# RealWorld, a #)
m (STM a -> State# RealWorld -> (# State# RealWorld, a #)
forall a. STM a -> State# RealWorld -> (# State# RealWorld, a #)
unSTM STM a
e) State# RealWorld
s

-- | A variant of 'throw' that can only be used within the 'STM' monad.
--
-- Throwing an exception in @STM@ aborts the transaction and propagates the
-- exception. If the exception is caught via 'catchSTM', only the changes
-- enclosed by the catch are rolled back; changes made outside of 'catchSTM'
-- persist.
--
-- If the exception is not caught inside of the 'STM', it is re-thrown by
-- 'atomically', and the entire 'STM' is rolled back.
--
-- Although 'throwSTM' has a type that is an instance of the type of 'throw', the
-- two functions are subtly different:
--
-- > throw e    `seq` x  ===> throw e
-- > throwSTM e `seq` x  ===> x
--
-- The first example will cause the exception @e@ to be raised,
-- whereas the second one won\'t.  In fact, 'throwSTM' will only cause
-- an exception to be raised when it is used within the 'STM' monad.
-- The 'throwSTM' variant should be used in preference to 'throw' to
-- raise an exception within the 'STM' monad because it guarantees
-- ordering with respect to other 'STM' operations, whereas 'throw'
-- does not.
throwSTM :: Exception e => e -> STM a
throwSTM :: forall e a. Exception e => e -> STM a
throwSTM e
e = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, a #)) -> STM a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a b. (a -> b) -> a -> b
$ SomeException -> State# RealWorld -> (# State# RealWorld, a #)
forall a b. a -> State# RealWorld -> (# State# RealWorld, b #)
raiseIO# (e -> SomeException
forall e. Exception e => e -> SomeException
toException e
e)

-- | Exception handling within STM actions.
--
-- @'catchSTM' m f@ catches any exception thrown by @m@ using 'throwSTM',
-- using the function @f@ to handle the exception. If an exception is
-- thrown, any changes made by @m@ are rolled back, but changes prior to
-- @m@ persist.
catchSTM :: Exception e => STM a -> (e -> STM a) -> STM a
catchSTM :: forall e a. Exception e => STM a -> (e -> STM a) -> STM a
catchSTM (STM State# RealWorld -> (# State# RealWorld, a #)
m) e -> STM a
handler = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, a #)) -> STM a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a b. (a -> b) -> a -> b
$ (State# RealWorld -> (# State# RealWorld, a #))
-> (SomeException -> State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld
-> (# State# RealWorld, a #)
forall a b.
(State# RealWorld -> (# State# RealWorld, a #))
-> (b -> State# RealWorld -> (# State# RealWorld, a #))
-> State# RealWorld
-> (# State# RealWorld, a #)
catchSTM# State# RealWorld -> (# State# RealWorld, a #)
m SomeException -> State# RealWorld -> (# State# RealWorld, a #)
handler'
    where
      handler' :: SomeException -> State# RealWorld -> (# State# RealWorld, a #)
handler' SomeException
e = case SomeException -> Maybe e
forall e. Exception e => SomeException -> Maybe e
fromException SomeException
e of
                     Just e
e' -> STM a -> State# RealWorld -> (# State# RealWorld, a #)
forall a. STM a -> State# RealWorld -> (# State# RealWorld, a #)
unSTM (e -> STM a
handler e
e')
                     Maybe e
Nothing -> SomeException -> State# RealWorld -> (# State# RealWorld, a #)
forall a b. a -> State# RealWorld -> (# State# RealWorld, b #)
raiseIO# SomeException
e

-- |Shared memory locations that support atomic memory transactions.
data TVar a = TVar (TVar# RealWorld a)

-- | @since base-4.8.0.0
instance Eq (TVar a) where
        (TVar TVar# RealWorld a
tvar1#) == :: TVar a -> TVar a -> Bool
== (TVar TVar# RealWorld a
tvar2#) = Int# -> Bool
isTrue# (TVar# RealWorld a -> TVar# RealWorld a -> Int#
forall s a. TVar# s a -> TVar# s a -> Int#
sameTVar# TVar# RealWorld a
tvar1# TVar# RealWorld a
tvar2#)

-- | Create a new 'TVar' holding a value supplied
newTVar :: a -> STM (TVar a)
newTVar :: forall a. a -> STM (TVar a)
newTVar a
val = (State# RealWorld -> (# State# RealWorld, TVar a #))
-> STM (TVar a)
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, TVar a #))
 -> STM (TVar a))
-> (State# RealWorld -> (# State# RealWorld, TVar a #))
-> STM (TVar a)
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s1# ->
    case a -> State# RealWorld -> (# State# RealWorld, TVar# RealWorld a #)
forall a d. a -> State# d -> (# State# d, TVar# d a #)
newTVar# a
val State# RealWorld
s1# of
         (# State# RealWorld
s2#, TVar# RealWorld a
tvar# #) -> (# State# RealWorld
s2#, TVar# RealWorld a -> TVar a
forall a. TVar# RealWorld a -> TVar a
TVar TVar# RealWorld a
tvar# #)

-- | @IO@ version of 'newTVar'.  This is useful for creating top-level
-- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
-- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
-- possible.
newTVarIO :: a -> IO (TVar a)
newTVarIO :: forall a. a -> IO (TVar a)
newTVarIO a
val = (State# RealWorld -> (# State# RealWorld, TVar a #)) -> IO (TVar a)
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, TVar a #))
 -> IO (TVar a))
-> (State# RealWorld -> (# State# RealWorld, TVar a #))
-> IO (TVar a)
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s1# ->
    case a -> State# RealWorld -> (# State# RealWorld, TVar# RealWorld a #)
forall a d. a -> State# d -> (# State# d, TVar# d a #)
newTVar# a
val State# RealWorld
s1# of
         (# State# RealWorld
s2#, TVar# RealWorld a
tvar# #) -> (# State# RealWorld
s2#, TVar# RealWorld a -> TVar a
forall a. TVar# RealWorld a -> TVar a
TVar TVar# RealWorld a
tvar# #)

-- | Return the current value stored in a 'TVar'.
-- This is equivalent to
--
-- >  readTVarIO = atomically . readTVar
--
-- but works much faster, because it doesn't perform a complete
-- transaction, it just reads the current value of the 'TVar'.
readTVarIO :: TVar a -> IO a
readTVarIO :: forall a. TVar a -> IO a
readTVarIO (TVar TVar# RealWorld a
tvar#) = (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
IO ((State# RealWorld -> (# State# RealWorld, a #)) -> IO a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> IO a
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s# -> TVar# RealWorld a -> State# RealWorld -> (# State# RealWorld, a #)
forall d a. TVar# d a -> State# d -> (# State# d, a #)
readTVarIO# TVar# RealWorld a
tvar# State# RealWorld
s#

-- |Return the current value stored in a 'TVar'.
readTVar :: TVar a -> STM a
readTVar :: forall a. TVar a -> STM a
readTVar (TVar TVar# RealWorld a
tvar#) = (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, a #)) -> STM a)
-> (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s# -> TVar# RealWorld a -> State# RealWorld -> (# State# RealWorld, a #)
forall d a. TVar# d a -> State# d -> (# State# d, a #)
readTVar# TVar# RealWorld a
tvar# State# RealWorld
s#

-- |Write the supplied value into a 'TVar'.
writeTVar :: TVar a -> a -> STM ()
writeTVar :: forall a. TVar a -> a -> STM ()
writeTVar (TVar TVar# RealWorld a
tvar#) a
val = (State# RealWorld -> (# State# RealWorld, () #)) -> STM ()
forall a. (State# RealWorld -> (# State# RealWorld, a #)) -> STM a
STM ((State# RealWorld -> (# State# RealWorld, () #)) -> STM ())
-> (State# RealWorld -> (# State# RealWorld, () #)) -> STM ()
forall a b. (a -> b) -> a -> b
$ \State# RealWorld
s1# ->
    case TVar# RealWorld a -> a -> State# RealWorld -> State# RealWorld
forall d a. TVar# d a -> a -> State# d -> State# d
writeTVar# TVar# RealWorld a
tvar# a
val State# RealWorld
s1# of
         State# RealWorld
s2# -> (# State# RealWorld
s2#, () #)

-----------------------------------------------------------------------------
-- MVar utilities
-----------------------------------------------------------------------------

-- | Provide an 'IO' action with the current value of an 'MVar'. The 'MVar'
-- will be empty for the duration that the action is running.
withMVar :: MVar a -> (a -> IO b) -> IO b
withMVar :: forall a b. MVar a -> (a -> IO b) -> IO b
withMVar MVar a
m a -> IO b
io =
  ((forall a. IO a -> IO a) -> IO b) -> IO b
forall b. ((forall a. IO a -> IO a) -> IO b) -> IO b
mask (((forall a. IO a -> IO a) -> IO b) -> IO b)
-> ((forall a. IO a -> IO a) -> IO b) -> IO b
forall a b. (a -> b) -> a -> b
$ \forall a. IO a -> IO a
restore -> do
    a <- MVar a -> IO a
forall a. MVar a -> IO a
takeMVar MVar a
m
    b <- catchAny (restore (io a))
            (\e
e -> do MVar a -> a -> IO ()
forall a. MVar a -> a -> IO ()
putMVar MVar a
m a
a; e -> IO b
forall a e. (HasCallStack, Exception e) => e -> a
throw e
e)
    putMVar m a
    return b

-- | Modify the value of an 'MVar'.
modifyMVar_ :: MVar a -> (a -> IO a) -> IO ()
modifyMVar_ :: forall a. MVar a -> (a -> IO a) -> IO ()
modifyMVar_ MVar a
m a -> IO a
io =
  ((forall a. IO a -> IO a) -> IO ()) -> IO ()
forall b. ((forall a. IO a -> IO a) -> IO b) -> IO b
mask (((forall a. IO a -> IO a) -> IO ()) -> IO ())
-> ((forall a. IO a -> IO a) -> IO ()) -> IO ()
forall a b. (a -> b) -> a -> b
$ \forall a. IO a -> IO a
restore -> do
    a <- MVar a -> IO a
forall a. MVar a -> IO a
takeMVar MVar a
m
    a' <- catchAny (restore (io a))
            (\e
e -> do MVar a -> a -> IO ()
forall a. MVar a -> a -> IO ()
putMVar MVar a
m a
a; e -> IO a
forall a e. (HasCallStack, Exception e) => e -> a
throw e
e)
    putMVar m a'
    return ()

-----------------------------------------------------------------------------
-- Thread waiting
-----------------------------------------------------------------------------

-- Machinery needed to ensure that we only have one copy of certain
-- CAFs in this module even when the base package is present twice, as
-- it is when base is dynamically loaded into GHCi.  The RTS keeps
-- track of the single true value of the CAF, so even when the CAFs in
-- the dynamically-loaded base package are reverted, nothing bad
-- happens.
--
sharedCAF :: a -> (Ptr a -> IO (Ptr a)) -> IO a
sharedCAF :: forall a. a -> (Ptr a -> IO (Ptr a)) -> IO a
sharedCAF a
a Ptr a -> IO (Ptr a)
get_or_set =
   IO a -> IO a
forall a. IO a -> IO a
mask_ (IO a -> IO a) -> IO a -> IO a
forall a b. (a -> b) -> a -> b
$ do
     stable_ref <- a -> IO (StablePtr a)
forall a. a -> IO (StablePtr a)
newStablePtr a
a
     let ref = Ptr () -> Ptr b
forall a b. Ptr a -> Ptr b
castPtr (StablePtr a -> Ptr ()
forall a. StablePtr a -> Ptr ()
castStablePtrToPtr StablePtr a
stable_ref)
     ref2 <- get_or_set ref
     if ref==ref2
        then return a
        else do freeStablePtr stable_ref
                deRefStablePtr (castPtrToStablePtr (castPtr ref2))

reportStackOverflow :: IO ()
reportStackOverflow :: IO ()
reportStackOverflow = do
     ThreadId tid <- IO ThreadId
myThreadId
     c_reportStackOverflow tid

reportError :: SomeException -> IO ()
reportError :: SomeException -> IO ()
reportError SomeException
ex = do
   handler <- IO (SomeException -> IO ())
getUncaughtExceptionHandler
   handler ex

-- SUP: Are the hooks allowed to re-enter Haskell land?  If so, remove
-- the unsafe below.
foreign import ccall unsafe "reportStackOverflow"
        c_reportStackOverflow :: ThreadId# -> IO ()

foreign import ccall unsafe "reportHeapOverflow"
        reportHeapOverflow :: IO ()

{-# NOINLINE uncaughtExceptionHandler #-}
uncaughtExceptionHandler :: IORef (SomeException -> IO ())
uncaughtExceptionHandler :: IORef (SomeException -> IO ())
uncaughtExceptionHandler = IO (IORef (SomeException -> IO ()))
-> IORef (SomeException -> IO ())
forall a. IO a -> a
unsafePerformIO ((SomeException -> IO ()) -> IO (IORef (SomeException -> IO ()))
forall a. a -> IO (IORef a)
newIORef SomeException -> IO ()
defaultHandler)
   where
      defaultHandler :: SomeException -> IO ()
      defaultHandler :: SomeException -> IO ()
defaultHandler SomeException
se = do
         (Handle -> IO ()
hFlush Handle
stdout) IO () -> (forall e. Exception e => e -> IO ()) -> IO ()
forall a. IO a -> (forall e. Exception e => e -> IO a) -> IO a
`catchAny` (\ e
_ -> () -> IO ()
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ())
         let msg :: String
msg = SomeException -> String
forall e. Exception e => e -> String
displayException SomeException
se
         String -> (CString -> IO ()) -> IO ()
forall a. String -> (CString -> IO a) -> IO a
withCString String
"%s" ((CString -> IO ()) -> IO ()) -> (CString -> IO ()) -> IO ()
forall a b. (a -> b) -> a -> b
$ \CString
cfmt ->
          String -> (CString -> IO ()) -> IO ()
forall a. String -> (CString -> IO a) -> IO a
withCString String
msg ((CString -> IO ()) -> IO ()) -> (CString -> IO ()) -> IO ()
forall a b. (a -> b) -> a -> b
$ \CString
cmsg ->
            CString -> CString -> IO ()
errorBelch CString
cfmt CString
cmsg

-- don't use errorBelch() directly, because we cannot call varargs functions
-- using the FFI.
foreign import ccall unsafe "HsBase.h errorBelch2"
   errorBelch :: CString -> CString -> IO ()

setUncaughtExceptionHandler :: (SomeException -> IO ()) -> IO ()
setUncaughtExceptionHandler :: (SomeException -> IO ()) -> IO ()
setUncaughtExceptionHandler = IORef (SomeException -> IO ()) -> (SomeException -> IO ()) -> IO ()
forall a. IORef a -> a -> IO ()
writeIORef IORef (SomeException -> IO ())
uncaughtExceptionHandler

getUncaughtExceptionHandler :: IO (SomeException -> IO ())
getUncaughtExceptionHandler :: IO (SomeException -> IO ())
getUncaughtExceptionHandler = IORef (SomeException -> IO ()) -> IO (SomeException -> IO ())
forall a. IORef a -> IO a
readIORef IORef (SomeException -> IO ())
uncaughtExceptionHandler