Commit ac08abc6 authored by Simon Marlow's avatar Simon Marlow
Browse files

Get the InteractiveContext right when stopped at a breakpoint

we shouldn't be binding 'it' until the computation has actually finished.
parent 6d075f13
......@@ -2132,7 +2132,7 @@ data RunResult
| RunBreak ThreadId [Name] BreakInfo ResumeHandle
data Status
= Break HValue BreakInfo ThreadId (MVar ()) (MVar Status) [Name]
= Break HValue BreakInfo ThreadId
-- ^ the computation hit a breakpoint
| Complete (Either Exception [HValue])
-- ^ the computation completed with either an exception or a value
......@@ -2145,9 +2145,15 @@ data ResumeHandle
(MVar ()) -- breakMVar
(MVar Status) -- statusMVar
[Name] -- [Name] to bind on completion
InteractiveContext -- IC on completion
InteractiveContext -- IC to restore on resumption
[Name] -- [Name] to remove from the link env
-- We need to track two InteractiveContexts:
-- - the IC before runStmt, which is restored on each resume
-- - the IC binding the results of the original statement, which
-- will be the IC when runStmt returns with RunOk.
-- | Run a statement in the current interactive context. Statement
-- may bind multple values.
runStmt :: Session -> String -> IO RunResult
......@@ -2167,38 +2173,40 @@ runStmt (Session ref) expr
case maybe_stuff of
Nothing -> return RunFailed
Just (new_hsc_env, names, hval) -> do
writeIORef ref new_hsc_env
Just (new_IC, names, hval) -> do
-- set the onBreakAction to be performed when we hit a
-- breakpoint this is visible in the Byte Code
-- Interpreter, thus it is a global variable,
-- implemented with stable pointers
stablePtr <- setBreakAction breakMVar statusMVar names
stablePtr <- setBreakAction breakMVar statusMVar
let thing_to_run = unsafeCoerce# hval :: IO [HValue]
status <- sandboxIO statusMVar thing_to_run
freeStablePtr stablePtr -- be careful not to leak stable pointers!
handleRunStatus ref (hsc_IC new_hsc_env) names status
handleRunStatus ref new_IC names (hsc_IC hsc_env)
breakMVar statusMVar status
handleRunStatus ref ic names status =
handleRunStatus ref final_ic final_names resume_ic breakMVar statusMVar status =
case status of
-- did we hit a breakpoint or did we complete?
(Break apStack info tid breakMVar statusMVar final_names) -> do
(Break apStack info tid) -> do
hsc_env <- readIORef ref
(new_hsc_env, names) <- extendEnvironment hsc_env apStack
(breakInfo_vars info)
writeIORef ref new_hsc_env
let res = ResumeHandle breakMVar statusMVar final_names
ic names
final_ic resume_ic names
return (RunBreak tid names info res)
(Complete either_hvals) ->
case either_hvals of
Left e -> return (RunException e)
Right hvals -> do
Linker.extendLinkEnv (zip names hvals)
return (RunOk names)
hsc_env <- readIORef ref
writeIORef ref hsc_env{hsc_IC=final_ic}
Linker.extendLinkEnv (zip final_names hvals)
return (RunOk final_names)
-- this points to the IO action that is executed when a breakpoint is hit
foreign import ccall "&breakPointIOAction"
breakPointIOAction :: Ptr (StablePtr (BreakInfo -> HValue -> IO ()))
......@@ -2214,33 +2222,33 @@ sandboxIO statusMVar thing = do
putMVar interruptTargetThread (child:ts)
takeMVar statusMVar `finally` modifyMVar_ interruptTargetThread (return.tail)
setBreakAction breakMVar statusMVar final_names = do
setBreakAction breakMVar statusMVar = do
stablePtr <- newStablePtr onBreak
poke breakPointIOAction stablePtr
return stablePtr
where onBreak ids apStack = do
tid <- myThreadId
putMVar statusMVar (Break apStack ids tid breakMVar statusMVar
putMVar statusMVar (Break apStack ids tid)
takeMVar breakMVar
resume :: Session -> ResumeHandle -> IO RunResult
resume (Session ref) res@(ResumeHandle breakMVar statusMVar
final_names ic names)
final_names final_ic resume_ic names)
= do
-- restore the original interactive context. This is not entirely
-- satisfactory: any new bindings made since the breakpoint stopped
-- will be dropped from the interactive context, but not from the
-- linker's environment.
hsc_env <- readIORef ref
writeIORef ref hsc_env{ hsc_IC = ic }
writeIORef ref hsc_env{ hsc_IC = resume_ic }
Linker.deleteFromLinkEnv names
stablePtr <- setBreakAction breakMVar statusMVar final_names
stablePtr <- setBreakAction breakMVar statusMVar
putMVar breakMVar () -- this awakens the stopped thread...
status <- takeMVar statusMVar -- and wait for the result
freeStablePtr stablePtr -- be careful not to leak stable pointers!
handleRunStatus ref ic names status
handleRunStatus ref final_ic final_names resume_ic
breakMVar statusMVar status
-- This version of sandboxIO runs the expression in a completely new
......@@ -797,7 +797,7 @@ A naked expression returns a singleton Name [it].
hscStmt -- Compile a stmt all the way to an HValue, but don't run it
:: HscEnv
-> String -- The statement
-> IO (Maybe (HscEnv, [Name], HValue))
-> IO (Maybe (InteractiveContext, [Name], HValue))
hscStmt hsc_env stmt
= do { maybe_stmt <- hscParseStmt (hsc_dflags hsc_env) stmt
......@@ -828,7 +828,7 @@ hscStmt hsc_env stmt
; let src_span = srcLocSpan interactiveSrcLoc
; hval <- compileExpr hsc_env src_span ds_expr
; return (Just (hsc_env{ hsc_IC=new_ic }, bound_names, hval))
; return (Just (new_ic, bound_names, hval))
hscTcExpr -- Typecheck an expression (but don't run it)
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