Fix #1620: ModBreaks.modBreaks_array not initialised

After a :cd command and after setting some package flags,
GHCi unloads all loaded modules by resetting the list of targets.

This patch deletes eventually defined debugger breakpoints, before GHCi resets the target list.

The common code is factored out into the new function clearAllTargets.

5 files changed, 45 insertions, 7 deletions

diff --git a/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index ab3992ccd0..31c6db055d 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -1543,8 +1543,8 @@ changeDirectory dir = do
   graph <- GHC.getModuleGraph
   when (not (null $ GHC.mgModSummaries graph)) $
         liftIO $ putStrLn "Warning: changing directory causes all loaded modules to be unloaded,\nbecause the search path has changed."
-  GHC.setTargets []
-  _ <- GHC.load LoadAllTargets
+  -- delete targets and all eventually defined breakpoints (#1620)
+  clearAllTargets
   setContextAfterLoad False []
   GHC.workingDirectoryChanged
   dir' <- expandPath dir
@@ -1852,9 +1852,7 @@ loadModule' files = do
 
   -- unload first
   _ <- GHC.abandonAll
-  discardActiveBreakPoints
-  GHC.setTargets []
-  _ <- GHC.load LoadAllTargets
+  clearAllTargets
 
   GHC.setTargets targets
   success <- doLoadAndCollectInfo False LoadAllTargets
@@ -2916,8 +2914,8 @@ newDynFlags interactive_only minus_opts = do
           when (verbosity dflags2 > 0) $
             liftIO . putStrLn $
               "package flags have changed, resetting and loading new packages..."
-          GHC.setTargets []
-          _ <- GHC.load LoadAllTargets
+          -- delete targets and all eventually defined breakpoints. (#1620)
+          clearAllTargets
           liftIO $ linkPackages hsc_env new_pkgs
           -- package flags changed, we can't re-use any of the old context
           setContextAfterLoad False []
@@ -4128,3 +4126,9 @@ wantNameFromInterpretedModule noCanDo str and_then =
                then noCanDo n $ text "module " <> ppr modl <>
                                 text " is not interpreted"
                else and_then n
+
+clearAllTargets :: GhciMonad m => m ()
+clearAllTargets = discardActiveBreakPoints
+                >> GHC.setTargets []
+                >> GHC.load LoadAllTargets
+                >> pure ()
diff --git a/testsuite/tests/ghci.debugger/scripts/T1620.script b/testsuite/tests/ghci.debugger/scripts/T1620.script
new file mode 100644
index 0000000000..17d38d5530
--- /dev/null
+++ b/testsuite/tests/ghci.debugger/scripts/T1620.script
@@ -0,0 +1,18 @@
+-- Test 1: No hanging breakpoints after :cd
+:cd T1620
+:l T1620.hs
+:break 2
+:cd ..
+:break 2
+:show breaks
+:cd T1620
+:l T1620.hs
+:main
+:l T1620.hs
+-- Test 2: Non hanging breakpoints after :set <some-package-flag>
+:break 2
+:set -no-user-package-db
+:show breaks
+:l T1620.hs
+:main
+:l T1620.hs
diff --git a/testsuite/tests/ghci.debugger/scripts/T1620.stdout b/testsuite/tests/ghci.debugger/scripts/T1620.stdout
new file mode 100644
index 0000000000..fc453c2b60
--- /dev/null
+++ b/testsuite/tests/ghci.debugger/scripts/T1620.stdout
@@ -0,0 +1,9 @@
+Breakpoint 0 activated at T1620.hs:2:16-47
+Warning: changing directory causes all loaded modules to be unloaded,
+because the search path has changed.
+No modules are loaded with debugging support.
+No active breakpoints.
+[1,3,4,7,10]
+Breakpoint 1 activated at T1620.hs:2:16-47
+No active breakpoints.
+[1,3,4,7,10]
diff --git a/testsuite/tests/ghci.debugger/scripts/T1620/T1620.hs b/testsuite/tests/ghci.debugger/scripts/T1620/T1620.hs
new file mode 100644
index 0000000000..7c97826676
--- /dev/null
+++ b/testsuite/tests/ghci.debugger/scripts/T1620/T1620.hs
@@ -0,0 +1,5 @@
+qsort [] = []
+qsort (a:as) = qsort left ++ [a] ++ qsort right
+  where (left,right) = (filter (<=a) as, filter (>a) as)
+
+main = print $ qsort [4, 1, 7, 10, 3]
diff --git a/testsuite/tests/ghci.debugger/scripts/all.T b/testsuite/tests/ghci.debugger/scripts/all.T
index bc3d025dcd..8460fbb809 100644
--- a/testsuite/tests/ghci.debugger/scripts/all.T
+++ b/testsuite/tests/ghci.debugger/scripts/all.T
@@ -100,6 +100,8 @@ test('hist001', [extra_files(['../Test3.hs']), extra_run_opts('+RTS -I0')],
 test('hist002', [extra_files(['../Test3.hs']), extra_run_opts('+RTS -I0')],
      ghci_script, ['hist002.script'])
 
+test('T1620', extra_files(['T1620/', 'T1620/T1620.hs']),
+              ghci_script, ['T1620.script'])
 test('T2740', normal, ghci_script, ['T2740.script'])
 
 test('getargs', extra_files(['../getargs.hs']), ghci_script, ['getargs.script'])