GHCi.hs 18.2 KB
Newer Older
1 2 3 4 5 6 7 8
{-# LANGUAGE RecordWildCards, ScopedTypeVariables, BangPatterns, CPP #-}

--
-- | Interacting with the interpreter, whether it is running on an
-- external process or in the current process.
--
module GHCi
  ( -- * High-level interface to the interpreter
9
    evalStmt, EvalStatus_(..), EvalStatus, EvalResult(..), EvalExpr(..)
10 11 12 13 14 15
  , resumeStmt
  , abandonStmt
  , evalIO
  , evalString
  , evalStringToIOString
  , mallocData
16 17
  , mkCostCentre
  , costCentreStackInfo
18 19 20
  , newBreakArray
  , enableBreakpoint
  , breakpointStatus
21
  , getBreakpointVar
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

  -- * The object-code linker
  , initObjLinker
  , lookupSymbol
  , lookupClosure
  , loadDLL
  , loadArchive
  , loadObj
  , unloadObj
  , addLibrarySearchPath
  , removeLibrarySearchPath
  , resolveObjs
  , findSystemLibrary

  -- * Lower-level API using messages
  , iservCmd, Message(..), withIServ, stopIServ
  , iservCall, readIServ, writeIServ
  , purgeLookupSymbolCache
  , freeHValueRefs
  , mkFinalizedHValue
  , wormhole, wormholeRef
  , mkEvalOpts
  , fromEvalResult
  ) where

import GHCi.Message
import GHCi.Run
import GHCi.RemoteTypes
50
import GHCi.BreakArray (BreakArray)
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69
import HscTypes
import UniqFM
import Panic
import DynFlags
#ifndef mingw32_HOST_OS
import ErrUtils
import Outputable
#endif
import Exception
import BasicTypes
import FastString

import Control.Concurrent
import Control.Monad
import Control.Monad.IO.Class
import Data.Binary
import Data.ByteString (ByteString)
import Data.IORef
import Foreign
70 71
import Foreign.C
import GHC.Stack.CCS (CostCentre,CostCentreStack)
72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187
import System.Exit
#ifndef mingw32_HOST_OS
import Data.Maybe
import System.Posix as Posix
#endif
import System.Process

{- Note [Remote GHCi]

When the flag -fexternal-interpreter is given to GHC, interpreted code
is run in a separate process called iserv, and we communicate with the
external process over a pipe using Binary-encoded messages.

Motivation
~~~~~~~~~~

When the interpreted code is running in a separate process, it can
use a different "way", e.g. profiled or dynamic.  This means

- compiling Template Haskell code with -prof does not require
  building the code without -prof first

- when GHC itself is profiled, it can interpret unprofiled code,
  and the same applies to dynamic linking.

- An unprofiled GHCi can load and run profiled code, which means it
  can use the stack-trace functionality provided by profiling without
  taking the performance hit on the compiler that profiling would
  entail.

For other reasons see RemoteGHCi on the wiki.

Implementation Overview
~~~~~~~~~~~~~~~~~~~~~~~

The main pieces are:

- libraries/ghci, containing:
  - types for talking about remote values (GHCi.RemoteTypes)
  - the message protocol (GHCi.Message),
  - implementation of the messages (GHCi.Run)
  - implementation of Template Haskell (GHCi.TH)
  - a few other things needed to run interpreted code

- top-level iserv directory, containing the codefor the external
  server.  This is a fairly simple wrapper, most of the functionality
  is provided by modules in libraries/ghci.

- This module (GHCi) which provides the interface to the server used
  by the rest of GHC.

GHC works with and without -fexternal-interpreter.  With the flag, all
interpreted code is run by the iserv binary.  Without the flag,
interpreted code is run in the same process as GHC.

Things that do not work with -fexternal-interpreter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

dynCompileExpr cannot work, because we have no way to run code of an
unknown type in the remote process.  This API fails with an error
message if it is used with -fexternal-interpreter.
-}

-- | Run a command in the interpreter's context.  With
-- @-fexternal-interpreter@, the command is serialized and sent to an
-- external iserv process, and the response is deserialized (hence the
-- @Binary@ constraint).  With @-fno-external-interpreter@ we execute
-- the command directly here.
iservCmd :: Binary a => HscEnv -> Message a -> IO a
iservCmd hsc_env@HscEnv{..} msg
 | gopt Opt_ExternalInterpreter hsc_dflags =
     withIServ hsc_env $ \iserv ->
       uninterruptibleMask_ $ do -- Note [uninterruptibleMask_]
         iservCall iserv msg
 | otherwise = -- Just run it directly
   run msg


-- Note [uninterruptibleMask_ and iservCmd]
--
-- If we receive an async exception, such as ^C, while communicating
-- with the iserv process then we will be out-of-sync and not be able
-- to recoever.  Thus we use uninterruptibleMask_ during
-- communication.  A ^C will be delivered to the iserv process (because
-- signals get sent to the whole process group) which will interrupt
-- the running computation and return an EvalException result.

-- | Grab a lock on the 'IServ' and do something with it.
-- Overloaded because this is used from TcM as well as IO.
withIServ
  :: (MonadIO m, ExceptionMonad m)
  => HscEnv -> (IServ -> m a) -> m a
withIServ HscEnv{..} action =
  gmask $ \restore -> do
    m <- liftIO $ takeMVar hsc_iserv
      -- start the iserv process if we haven't done so yet
    iserv <- maybe (liftIO $ startIServ hsc_dflags) return m
               `gonException` (liftIO $ putMVar hsc_iserv Nothing)
      -- free any ForeignHValues that have been garbage collected.
    let iserv' = iserv{ iservPendingFrees = [] }
    a <- (do
      liftIO $ when (not (null (iservPendingFrees iserv))) $
        iservCall iserv (FreeHValueRefs (iservPendingFrees iserv))
        -- run the inner action
      restore $ action iserv)
          `gonException` (liftIO $ putMVar hsc_iserv (Just iserv'))
    liftIO $ putMVar hsc_iserv (Just iserv')
    return a


-- -----------------------------------------------------------------------------
-- Wrappers around messages

-- | Execute an action of type @IO [a]@, returning 'ForeignHValue's for
-- each of the results.
evalStmt
188 189
  :: HscEnv -> Bool -> EvalExpr ForeignHValue
  -> IO (EvalStatus_ [ForeignHValue] [HValueRef])
190 191 192 193 194 195 196 197
evalStmt hsc_env step foreign_expr = do
  let dflags = hsc_dflags hsc_env
  status <- withExpr foreign_expr $ \expr ->
    iservCmd hsc_env (EvalStmt (mkEvalOpts dflags step) expr)
  handleEvalStatus hsc_env status
 where
  withExpr :: EvalExpr ForeignHValue -> (EvalExpr HValueRef -> IO a) -> IO a
  withExpr (EvalThis fhv) cont =
198
    withForeignRef fhv $ \hvref -> cont (EvalThis hvref)
199 200 201 202 203
  withExpr (EvalApp fl fr) cont =
    withExpr fl $ \fl' ->
    withExpr fr $ \fr' ->
    cont (EvalApp fl' fr')

204 205 206
resumeStmt
  :: HscEnv -> Bool -> ForeignRef (ResumeContext [HValueRef])
  -> IO (EvalStatus_ [ForeignHValue] [HValueRef])
207 208
resumeStmt hsc_env step resume_ctxt = do
  let dflags = hsc_dflags hsc_env
209
  status <- withForeignRef resume_ctxt $ \rhv ->
210 211 212
    iservCmd hsc_env (ResumeStmt (mkEvalOpts dflags step) rhv)
  handleEvalStatus hsc_env status

213
abandonStmt :: HscEnv -> ForeignRef (ResumeContext [HValueRef]) -> IO ()
214
abandonStmt hsc_env resume_ctxt = do
215
  withForeignRef resume_ctxt $ \rhv ->
216 217 218
    iservCmd hsc_env (AbandonStmt rhv)

handleEvalStatus
219 220
  :: HscEnv -> EvalStatus [HValueRef]
  -> IO (EvalStatus_ [ForeignHValue] [HValueRef])
221 222
handleEvalStatus hsc_env status =
  case status of
223
    EvalBreak a b c d e f -> return (EvalBreak a b c d e f)
224 225 226 227 228 229 230 231 232 233
    EvalComplete alloc res ->
      EvalComplete alloc <$> addFinalizer res
 where
  addFinalizer (EvalException e) = return (EvalException e)
  addFinalizer (EvalSuccess rs) = do
    EvalSuccess <$> mapM (mkFinalizedHValue hsc_env) rs

-- | Execute an action of type @IO ()@
evalIO :: HscEnv -> ForeignHValue -> IO ()
evalIO hsc_env fhv = do
234
  liftIO $ withForeignRef fhv $ \fhv ->
235 236 237 238 239
    iservCmd hsc_env (EvalIO fhv) >>= fromEvalResult

-- | Execute an action of type @IO String@
evalString :: HscEnv -> ForeignHValue -> IO String
evalString hsc_env fhv = do
240
  liftIO $ withForeignRef fhv $ \fhv ->
241 242 243 244 245
    iservCmd hsc_env (EvalString fhv) >>= fromEvalResult

-- | Execute an action of type @String -> IO String@
evalStringToIOString :: HscEnv -> ForeignHValue -> String -> IO String
evalStringToIOString hsc_env fhv str = do
246
  liftIO $ withForeignRef fhv $ \fhv ->
247 248 249 250 251
    iservCmd hsc_env (EvalStringToString fhv str) >>= fromEvalResult


-- | Allocate and store the given bytes in memory, returning a pointer
-- to the memory in the remote process.
252 253
mallocData :: HscEnv -> ByteString -> IO (RemotePtr ())
mallocData hsc_env bs = iservCmd hsc_env (MallocData bs)
254

255
mkCostCentre
256
  :: HscEnv -> RemotePtr CChar -> String -> String -> IO (RemotePtr CostCentre)
257 258 259 260
mkCostCentre hsc_env c_module name src =
  iservCmd hsc_env (MkCostCentre c_module name src)


261
costCentreStackInfo :: HscEnv -> RemotePtr CostCentreStack -> IO [String]
262 263
costCentreStackInfo hsc_env ccs =
  iservCmd hsc_env (CostCentreStackInfo ccs)
264

265 266 267 268 269 270 271 272 273 274 275 276 277 278 279
newBreakArray :: HscEnv -> Int -> IO (ForeignRef BreakArray)
newBreakArray hsc_env size = do
  breakArray <- iservCmd hsc_env (NewBreakArray size)
  mkFinalizedHValue hsc_env breakArray

enableBreakpoint :: HscEnv -> ForeignRef BreakArray -> Int -> Bool -> IO ()
enableBreakpoint hsc_env ref ix b = do
  withForeignRef ref $ \breakarray ->
    iservCmd hsc_env (EnableBreakpoint breakarray ix b)

breakpointStatus :: HscEnv -> ForeignRef BreakArray -> Int -> IO Bool
breakpointStatus hsc_env ref ix = do
  withForeignRef ref $ \breakarray ->
    iservCmd hsc_env (BreakpointStatus breakarray ix)

280 281 282 283 284
getBreakpointVar :: HscEnv -> ForeignHValue -> Int -> IO (Maybe ForeignHValue)
getBreakpointVar hsc_env ref ix =
  withForeignRef ref $ \apStack -> do
    mb <- iservCmd hsc_env (GetBreakpointVar apStack ix)
    mapM (mkFinalizedHValue hsc_env) mb
285

286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462
-- -----------------------------------------------------------------------------
-- Interface to the object-code linker

initObjLinker :: HscEnv -> IO ()
initObjLinker hsc_env = iservCmd hsc_env InitLinker

lookupSymbol :: HscEnv -> FastString -> IO (Maybe (Ptr ()))
lookupSymbol hsc_env@HscEnv{..} str
 | gopt Opt_ExternalInterpreter hsc_dflags =
     -- Profiling of GHCi showed a lot of time and allocation spent
     -- making cross-process LookupSymbol calls, so I added a GHC-side
     -- cache which sped things up quite a lot.  We have to be careful
     -- to purge this cache when unloading code though.
     withIServ hsc_env $ \iserv@IServ{..} -> do
       cache <- readIORef iservLookupSymbolCache
       case lookupUFM cache str of
         Just p -> return (Just p)
         Nothing -> do
           m <- uninterruptibleMask_ $
                    iservCall iserv (LookupSymbol (unpackFS str))
           case m of
             Nothing -> return Nothing
             Just r -> do
               let p = fromRemotePtr r
               writeIORef iservLookupSymbolCache $! addToUFM cache str p
               return (Just p)
 | otherwise =
   fmap fromRemotePtr <$> run (LookupSymbol (unpackFS str))

lookupClosure :: HscEnv -> String -> IO (Maybe HValueRef)
lookupClosure hsc_env str =
  iservCmd hsc_env (LookupClosure str)

purgeLookupSymbolCache :: HscEnv -> IO ()
purgeLookupSymbolCache hsc_env@HscEnv{..} =
 when (gopt Opt_ExternalInterpreter hsc_dflags) $
   withIServ hsc_env $ \IServ{..} ->
     writeIORef iservLookupSymbolCache emptyUFM


-- | loadDLL loads a dynamic library using the OS's native linker
-- (i.e. dlopen() on Unix, LoadLibrary() on Windows).  It takes either
-- an absolute pathname to the file, or a relative filename
-- (e.g. "libfoo.so" or "foo.dll").  In the latter case, loadDLL
-- searches the standard locations for the appropriate library.
--
-- Returns:
--
-- Nothing      => success
-- Just err_msg => failure
loadDLL :: HscEnv -> String -> IO (Maybe String)
loadDLL hsc_env str = iservCmd hsc_env (LoadDLL str)

loadArchive :: HscEnv -> String -> IO ()
loadArchive hsc_env str = iservCmd hsc_env (LoadArchive str)

loadObj :: HscEnv -> String -> IO ()
loadObj hsc_env str = iservCmd hsc_env (LoadObj str)

unloadObj :: HscEnv -> String -> IO ()
unloadObj hsc_env str = iservCmd hsc_env (UnloadObj str)

addLibrarySearchPath :: HscEnv -> String -> IO (Ptr ())
addLibrarySearchPath hsc_env str =
  fromRemotePtr <$> iservCmd hsc_env (AddLibrarySearchPath str)

removeLibrarySearchPath :: HscEnv -> Ptr () -> IO Bool
removeLibrarySearchPath hsc_env p =
  iservCmd hsc_env (RemoveLibrarySearchPath (toRemotePtr p))

resolveObjs :: HscEnv -> IO SuccessFlag
resolveObjs hsc_env = successIf <$> iservCmd hsc_env ResolveObjs

findSystemLibrary :: HscEnv -> String -> IO (Maybe String)
findSystemLibrary hsc_env str = iservCmd hsc_env (FindSystemLibrary str)


-- -----------------------------------------------------------------------------
-- Raw calls and messages

-- | Send a 'Message' and receive the response from the iserv process
iservCall :: Binary a => IServ -> Message a -> IO a
iservCall iserv@IServ{..} msg =
  remoteCall iservPipe msg
    `catch` \(e :: SomeException) -> handleIServFailure iserv e

-- | Read a value from the iserv process
readIServ :: IServ -> Get a -> IO a
readIServ iserv@IServ{..} get =
  readPipe iservPipe get
    `catch` \(e :: SomeException) -> handleIServFailure iserv e

-- | Send a value to the iserv process
writeIServ :: IServ -> Put -> IO ()
writeIServ iserv@IServ{..} put =
  writePipe iservPipe put
    `catch` \(e :: SomeException) -> handleIServFailure iserv e

handleIServFailure :: IServ -> SomeException -> IO a
handleIServFailure IServ{..} e = do
  ex <- getProcessExitCode iservProcess
  case ex of
    Just (ExitFailure n) ->
      throw (InstallationError ("ghc-iserv terminated (" ++ show n ++ ")"))
    _ -> do
      terminateProcess iservProcess
      _ <- waitForProcess iservProcess
      throw e

-- -----------------------------------------------------------------------------
-- Starting and stopping the iserv process

startIServ :: DynFlags -> IO IServ
#ifdef mingw32_HOST_OS
startIServ _ = panic "startIServ"
  -- should not be called, because we disable -fexternal-interpreter on Windows.
  -- (see DynFlags.makeDynFlagsConsistent)
#else
startIServ dflags = do
  let flavour
        | WayProf `elem` ways dflags = "-prof"
        | WayDyn `elem` ways dflags = "-dyn"
        | otherwise = ""
      prog = pgm_i dflags ++ flavour
      opts = getOpts dflags opt_i
  debugTraceMsg dflags 3 $ text "Starting " <> text prog
  (rfd1, wfd1) <- Posix.createPipe -- we read on rfd1
  (rfd2, wfd2) <- Posix.createPipe -- we write on wfd2
  setFdOption rfd1 CloseOnExec True
  setFdOption wfd2 CloseOnExec True
  let args = show wfd1 : show rfd2 : opts
  (_, _, _, ph) <- createProcess (proc prog args)
  closeFd wfd1
  closeFd rfd2
  rh <- fdToHandle rfd1
  wh <- fdToHandle wfd2
  lo_ref <- newIORef Nothing
  cache_ref <- newIORef emptyUFM
  return $ IServ
    { iservPipe = Pipe { pipeRead = rh
                       , pipeWrite = wh
                       , pipeLeftovers = lo_ref }
    , iservProcess = ph
    , iservLookupSymbolCache = cache_ref
    , iservPendingFrees = []
    }
#endif

stopIServ :: HscEnv -> IO ()
#ifdef mingw32_HOST_OS
stopIServ _ = return ()
#else
stopIServ HscEnv{..} =
  gmask $ \_restore -> do
    m <- takeMVar hsc_iserv
    maybe (return ()) stop m
    putMVar hsc_iserv Nothing
 where
  stop iserv = do
    ex <- getProcessExitCode (iservProcess iserv)
    if isJust ex
       then return ()
       else iservCall iserv Shutdown
#endif

-- -----------------------------------------------------------------------------
{- Note [External GHCi pointers]

We have the following ways to reference things in GHCi:

HValue
------

HValue is a direct reference to an value in the local heap.  Obviously
we cannot use this to refer to things in the external process.


463
RemoteRef
464 465
---------

466
RemoteRef is a StablePtr to a heap-resident value.  When
467
-fexternal-interpreter is used, this value resides in the external
468
process's heap.  RemoteRefs are mostly used to send pointers in
469 470
messages between GHC and iserv.

471
A RemoteRef must be explicitly freed when no longer required, using
472 473
freeHValueRefs, or by attaching a finalizer with mkForeignHValue.

474
To get from a RemoteRef to an HValue you can use 'wormholeRef', which
475 476
fails with an error message if -fexternal-interpreter is in use.

477 478
ForeignRef
----------
479

480 481
A ForeignRef is a RemoteRef with a finalizer that will free the
'RemoteRef' when it is gargabe collected.  We mostly use ForeignHValue
482 483
on the GHC side.

484 485
The finalizer adds the RemoteRef to the iservPendingFrees list in the
IServ record.  The next call to iservCmd will free any RemoteRefs in
486 487 488 489 490
the list.  It was done this way rather than calling iservCmd directly,
because I didn't want to have arbitrary threads calling iservCmd.  In
principle it would probably be ok, but it seems less hairy this way.
-}

491 492
-- | Creates a 'ForeignRef' that will automatically release the
-- 'RemoteRef' when it is no longer referenced.
493 494
mkFinalizedHValue :: HscEnv -> RemoteRef a -> IO (ForeignRef a)
mkFinalizedHValue HscEnv{..} rref = mkForeignRef rref free
495 496
 where
  !external = gopt Opt_ExternalInterpreter hsc_dflags
497
  hvref = toHValueRef rref
498 499 500

  free :: IO ()
  free
501
    | not external = freeRemoteRef hvref
502 503 504 505 506 507 508 509 510 511 512
    | otherwise =
      modifyMVar_ hsc_iserv $ \mb_iserv ->
        case mb_iserv of
          Nothing -> return Nothing -- already shut down
          Just iserv@IServ{..} ->
            return (Just iserv{iservPendingFrees = hvref : iservPendingFrees})

freeHValueRefs :: HscEnv -> [HValueRef] -> IO ()
freeHValueRefs _ [] = return ()
freeHValueRefs hsc_env refs = iservCmd hsc_env (FreeHValueRefs refs)

513 514 515
-- | Convert a 'ForeignRef' to the value it references directly.  This
-- only works when the interpreter is running in the same process as
-- the compiler, so it fails when @-fexternal-interpreter@ is on.
516 517
wormhole :: DynFlags -> ForeignRef a -> IO a
wormhole dflags r = wormholeRef dflags (unsafeForeignRefToRemoteRef r)
518

519 520 521
-- | Convert an 'RemoteRef' to the value it references directly.  This
-- only works when the interpreter is running in the same process as
-- the compiler, so it fails when @-fexternal-interpreter@ is on.
522
wormholeRef :: DynFlags -> RemoteRef a -> IO a
523 524 525 526 527
wormholeRef dflags r
  | gopt Opt_ExternalInterpreter dflags
  = throwIO (InstallationError
      "this operation requires -fno-external-interpreter")
  | otherwise
528
  = localRef r
529 530 531 532 533 534 535 536 537 538 539 540 541 542 543

-- -----------------------------------------------------------------------------
-- Misc utils

mkEvalOpts :: DynFlags -> Bool -> EvalOpts
mkEvalOpts dflags step =
  EvalOpts
    { useSandboxThread = gopt Opt_GhciSandbox dflags
    , singleStep = step
    , breakOnException = gopt Opt_BreakOnException dflags
    , breakOnError = gopt Opt_BreakOnError dflags }

fromEvalResult :: EvalResult a -> IO a
fromEvalResult (EvalException e) = throwIO (fromSerializableException e)
fromEvalResult (EvalSuccess a) = return a