X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FIOBase.lhs;h=32c79410804f8804af2a43bb268bc9b2fb8e2dae;hb=26d2805a6e58822d246cf9601fb226b0861e7f65;hp=07273f925944ae61f04e27f2c8828e37f3ccf3ae;hpb=19de173b1bd4fa8cf1854cfefa619565910137f3;p=haskell-directory.git diff --git a/GHC/IOBase.lhs b/GHC/IOBase.lhs index 07273f9..32c7941 100644 --- a/GHC/IOBase.lhs +++ b/GHC/IOBase.lhs @@ -1,5 +1,5 @@ \begin{code} -{-# OPTIONS -fno-implicit-prelude #-} +{-# OPTIONS_GHC -fno-implicit-prelude #-} ----------------------------------------------------------------------------- -- | -- Module : GHC.IOBase @@ -14,21 +14,52 @@ -- ----------------------------------------------------------------------------- -module GHC.IOBase where - +-- #hide +module GHC.IOBase( + IO(..), unIO, failIO, liftIO, bindIO, thenIO, returnIO, + unsafePerformIO, unsafeInterleaveIO, + unsafeDupablePerformIO, unsafeDupableInterleaveIO, + noDuplicate, + + -- To and from from ST + stToIO, ioToST, unsafeIOToST, unsafeSTToIO, + + -- References + IORef(..), newIORef, readIORef, writeIORef, + IOArray(..), newIOArray, readIOArray, writeIOArray, unsafeReadIOArray, unsafeWriteIOArray, + MVar(..), + + -- Handles, file descriptors, + FilePath, + Handle(..), Handle__(..), HandleType(..), IOMode(..), FD, + isReadableHandleType, isWritableHandleType, isReadWriteHandleType, showHandle, + + -- Buffers + Buffer(..), RawBuffer, BufferState(..), BufferList(..), BufferMode(..), + bufferIsWritable, bufferEmpty, bufferFull, + + -- Exceptions + Exception(..), ArithException(..), AsyncException(..), ArrayException(..), + stackOverflow, heapOverflow, throw, throwIO, ioException, + IOError, IOException(..), IOErrorType(..), ioError, userError, + ExitCode(..) + ) where + import GHC.ST import GHC.Arr -- to derive Ix class import GHC.Enum -- to derive Enum class import GHC.STRef import GHC.Base -import GHC.Num -- To get fromInteger etc, needed because of -fno-implicit-prelude +-- import GHC.Num -- To get fromInteger etc, needed because of -fno-implicit-prelude import Data.Maybe ( Maybe(..) ) import GHC.Show import GHC.List import GHC.Read +import Foreign.C.Types (CInt) #ifndef __HADDOCK__ -import {-# SOURCE #-} Data.Dynamic +import {-# SOURCE #-} Data.Typeable ( showsTypeRep ) +import {-# SOURCE #-} Data.Dynamic ( Dynamic, dynTypeRep ) #endif -- --------------------------------------------------------------------------- @@ -128,6 +159,9 @@ ioToST (IO m) = (ST m) unsafeIOToST :: IO a -> ST s a unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s +unsafeSTToIO :: ST s a -> IO a +unsafeSTToIO (ST m) = IO (unsafeCoerce# m) + -- --------------------------------------------------------------------------- -- Unsafe IO operations @@ -183,16 +217,42 @@ once you use 'unsafePerformIO'. Indeed, it is possible to write @coerce :: a -> b@ with the help of 'unsafePerformIO'. So be careful! -} -{-# NOINLINE unsafePerformIO #-} unsafePerformIO :: IO a -> a -unsafePerformIO (IO m) = case m realWorld# of (# _, r #) -> r +unsafePerformIO m = unsafeDupablePerformIO (noDuplicate >> m) + +{-| +This version of 'unsafePerformIO' is slightly more efficient, +because it omits the check that the IO is only being performed by a +single thread. Hence, when you write 'unsafeDupablePerformIO', +there is a possibility that the IO action may be performed multiple +times (on a multiprocessor), and you should therefore ensure that +it gives the same results each time. +-} +{-# NOINLINE unsafeDupablePerformIO #-} +unsafeDupablePerformIO :: IO a -> a +unsafeDupablePerformIO (IO m) = lazy (case m realWorld# of (# _, r #) -> r) --- Why do we NOINLINE unsafePerformIO? See the comment with +-- Why do we NOINLINE unsafeDupablePerformIO? See the comment with -- GHC.ST.runST. Essentially the issue is that the IO computation -- inside unsafePerformIO must be atomic: it must either all run, or -- not at all. If we let the compiler see the application of the IO -- to realWorld#, it might float out part of the IO. +-- Why is there a call to 'lazy' in unsafeDupablePerformIO? +-- If we don't have it, the demand analyser discovers the following strictness +-- for unsafeDupablePerformIO: C(U(AV)) +-- But then consider +-- unsafeDupablePerformIO (\s -> let r = f x in +-- case writeIORef v r s of (# s1, _ #) -> +-- (# s1, r #) +-- The strictness analyser will find that the binding for r is strict, +-- (becuase of uPIO's strictness sig), and so it'll evaluate it before +-- doing the writeIORef. This actually makes tests/lib/should_run/memo002 +-- get a deadlock! +-- +-- Solution: don't expose the strictness of unsafeDupablePerformIO, +-- by hiding it with 'lazy' + {-| 'unsafeInterleaveIO' allows 'IO' computation to be deferred lazily. When passed a value of type @IO a@, the 'IO' will only be performed @@ -201,15 +261,32 @@ file reading, see 'System.IO.hGetContents'. -} {-# INLINE unsafeInterleaveIO #-} unsafeInterleaveIO :: IO a -> IO a -unsafeInterleaveIO (IO m) +unsafeInterleaveIO m = unsafeDupableInterleaveIO (noDuplicate >> m) + +-- We believe that INLINE on unsafeInterleaveIO is safe, because the +-- state from this IO thread is passed explicitly to the interleaved +-- IO, so it cannot be floated out and shared. + +{-# INLINE unsafeDupableInterleaveIO #-} +unsafeDupableInterleaveIO :: IO a -> IO a +unsafeDupableInterleaveIO (IO m) = IO ( \ s -> let r = case m s of (# _, res #) -> res in (# s, r #)) --- We believe that INLINE on unsafeInterleaveIO is safe, because the --- state from this IO thread is passed explicitly to the interleaved --- IO, so it cannot be floated out and shared. +{-| +Ensures that the suspensions under evaluation by the current thread +are unique; that is, the current thread is not evaluating anything +that is also under evaluation by another thread that has also executed +'noDuplicate'. + +This operation is used in the definition of 'unsafePerformIO' to +prevent the IO action from being executed multiple times, which is usually +undesirable. +-} +noDuplicate :: IO () +noDuplicate = IO $ \s -> case noDuplicate# s of s' -> (# s', () #) -- --------------------------------------------------------------------------- -- Handle type @@ -266,6 +343,15 @@ instance Eq (MVar a) where -- enough information to identify the handle for debugging. A handle is -- equal according to '==' only to itself; no attempt -- is made to compare the internal state of different handles for equality. +-- +-- GHC note: a 'Handle' will be automatically closed when the garbage +-- collector detects that it has become unreferenced by the program. +-- However, relying on this behaviour is not generally recommended: +-- the garbage collector is unpredictable. If possible, use explicit +-- an explicit 'hClose' to close 'Handle's when they are no longer +-- required. GHC does not currently attempt to free up file +-- descriptors when they have run out, it is your responsibility to +-- ensure that this doesn't happen. data Handle = FileHandle -- A normal handle to a file @@ -287,7 +373,7 @@ instance Eq Handle where (DuplexHandle _ h1 _) == (DuplexHandle _ h2 _) = h1 == h2 _ == _ = False -type FD = Int -- XXX ToDo: should be CInt +type FD = CInt data Handle__ = Handle__ { @@ -387,6 +473,9 @@ isWritableHandleType WriteHandle = True isWritableHandleType ReadWriteHandle = True isWritableHandleType _ = False +isReadWriteHandleType ReadWriteHandle{} = True +isReadWriteHandleType _ = False + -- | File and directory names are values of type 'String', whose precise -- meaning is operating system dependent. Files can be opened, yielding a -- handle which can then be used to operate on the contents of that file. @@ -559,6 +648,14 @@ data Exception -- ^The current thread was executing a call to -- 'Control.Concurrent.MVar.takeMVar' that could never return, -- because there are no other references to this 'MVar'. + | BlockedIndefinitely + -- ^The current thread was waiting to retry an atomic memory transaction + -- that could never become possible to complete because there are no other + -- threads referring to any of teh TVars involved. + | NestedAtomically + -- ^The runtime detected an attempt to nest one STM transaction + -- inside another one, presumably due to the use of + -- 'unsafePeformIO' with 'atomically'. | Deadlock -- ^There are no runnable threads, so the program is -- deadlocked. The 'Deadlock' exception is @@ -693,9 +790,11 @@ instance Show Exception where showsPrec _ (RecConError err) = showString err showsPrec _ (RecUpdError err) = showString err showsPrec _ (AssertionFailed err) = showString err - showsPrec _ (DynException _err) = showString "unknown exception" + showsPrec _ (DynException err) = showString "exception :: " . showsTypeRep (dynTypeRep err) showsPrec _ (AsyncException e) = shows e showsPrec _ (BlockedOnDeadMVar) = showString "thread blocked indefinitely" + showsPrec _ (BlockedIndefinitely) = showString "thread blocked indefinitely" + showsPrec _ (NestedAtomically) = showString "Control.Concurrent.STM.atomically was nested" showsPrec _ (NonTermination) = showString "<>" showsPrec _ (Deadlock) = showString "<>" @@ -715,6 +814,7 @@ instance Eq Exception where AsyncException e1 == AsyncException e2 = e1 == e2 BlockedOnDeadMVar == BlockedOnDeadMVar = True NonTermination == NonTermination = True + NestedAtomically == NestedAtomically = True Deadlock == Deadlock = True _ == _ = False @@ -746,8 +846,8 @@ throw exception = raise# exception -- Although 'throwIO' has a type that is an instance of the type of 'throw', the -- two functions are subtly different: -- --- > throw e `seq` return () ===> throw e --- > throwIO e `seq` return () ===> return () +-- > throw e `seq` x ===> throw e +-- > throwIO e `seq` x ===> x -- -- The first example will cause the exception @e@ to be raised, -- whereas the second one won\'t. In fact, 'throwIO' will only cause