Handle breakpoint jumps while splicing TH functions in ghci

The dynamic linker has been modified so that it won't panic if one of the breakpointJump functions fails to resolve.
Now, if the dynamic linker fails to find a HValue for a Name, before looking for a static symbol it will ask to

Breakpoints.lookupBogusBreakpointVal :: Name -> Maybe HValue

which returns an identity function for the Jump names or Nothing else.

A TH function might contain a call to a breakpoint function. So if it is compiled to bytecodes, the breakpoints will be desugared to 'jumps'. Whenever this code is spliced, the linker will fail to find the jumpfunctions unless there is a default.

compiler/ghci/ByteCodeLink.lhs

@@ -27,6 +27,7 @@ import Module
 import PackageConfig
 import FastString
 import Panic
+import Breakpoints
 
 #ifdef DEBUG
 import Outputable
@@ -211,6 +212,8 @@ lookupName :: ClosureEnv -> Name -> IO HValue
 lookupName ce nm
    = case lookupNameEnv ce nm of
         Just (_,aa) -> return aa
+        Nothing | Just bk <- lookupBogusBreakpointVal nm
+           -> return bk
         Nothing 
            -> ASSERT2(isExternalName nm, ppr nm)
 	      do let sym_to_find = nameToCLabel nm "closure"

compiler/main/Breakpoints.hs

@@ -9,7 +9,16 @@
 
 module Breakpoints where
 
+#ifdef GHCI
+import {-#SOURCE#-} ByteCodeLink ( HValue ) 
+#endif
+
 import {-#SOURCE#-} HscTypes     ( Session )
+import Name
+import Var                       ( Id )
+import PrelNames
+
+import GHC.Exts                  ( unsafeCoerce# )
 
 data BkptHandler a = BkptHandler {
      handleBreakpoint  :: forall b. Session -> [(Id,HValue)] -> BkptLocation a ->  String -> b -> IO b
@@ -29,3 +38,16 @@ type Coord        = (Int, Int)
 
 noDbgSites :: SiteMap
 noDbgSites = []
+
+-- | Returns the 'identity' jumps
+--   Used to deal with spliced code, where we don't want breakpoints
+#ifdef GHCI
+lookupBogusBreakpointVal :: Name -> Maybe HValue
+lookupBogusBreakpointVal name 
+  | name == breakpointJumpName     = Just$ unsafeCoerce# (\_ _ _ _ a->a)
+  | name == breakpointAutoJumpName = Just$ unsafeCoerce# (\_ _ _ _ a->a)
+  | name == breakpointCondJumpName = Just$ unsafeCoerce# (\_ _ _ _ _ a->a)
+  | otherwise = Nothing
+#else 
+lookupBogusBreakpointVal _ = Nothing
+#endif //GHCI