Fix a crash when a stop hook deletes itself in its callback.

lldb/source/Commands/CommandObjectTarget.cpp

@@ -5121,6 +5121,15 @@ class CommandObjectTargetStopHookDelete : public CommandObjectParsed {
       : CommandObjectParsed(interpreter, "target stop-hook delete",
                             "Delete a stop-hook.",
                             "target stop-hook delete [<idx>]") {
+    SetHelpLong(
+        R"(
+Deletes the stop hook by index.
+
+At any given stop, all enabled stop hooks that pass the stop filter will
+get a chance to run.  That means if one stop-hook deletes another stop hook 
+while executing, the deleted stop hook will still fire for the stop at which 
+it was deleted.
+        )");
     AddSimpleArgumentList(eArgTypeStopHookID, eArgRepeatStar);
   }
 

lldb/source/Target/Target.cpp

@@ -3207,6 +3207,11 @@ bool Target::RunStopHooks(bool at_initial_stop) {
   bool should_stop = false;
   bool requested_continue = false;
 
+  // A stop hook might get deleted while running stop hooks.
+  // We have to decide what that means.  We will follow the rule that deleting
+  // a stop hook while processing these stop hooks will delete it for FUTURE
+  // stops but not this stop.  Fortunately, copying the m_stop_hooks to the
+  // active_hooks list before iterating over the hooks has this effect.
   for (auto cur_hook_sp : active_hooks) {
     bool any_thread_matched = false;
     for (auto exc_ctx : exc_ctx_with_reasons) {

lldb/test/API/commands/target/stop-hooks/TestStopHookScripted.py

@@ -48,6 +48,39 @@ def test_bad_handler(self):
             "Got the right error",
         )
 
+    def test_self_deleting(self):
+        """Test that we can handle a stop hook that deletes itself"""
+        self.script_setup()
+        # Run to the first breakpoint before setting the stop hook
+        # so we don't have to figure out where it showed up in the new
+        # target.
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+            self, "Stop here first", self.main_source_file
+        )
+
+        # Now add our stop hook and register it:
+        result = lldb.SBCommandReturnObject()
+        command = "target stop-hook add -P stop_hook.self_deleting_stop"
+        self.interp.HandleCommand(command, result)
+        self.assertCommandReturn(result, f"Added my stop hook: {result.GetError()}")
+
+        result_str = result.GetOutput()
+        p = re.compile("Stop hook #([0-9]+) added.")
+        m = p.match(result_str)
+        current_stop_hook_id = m.group(1)
+        command = "command script add -o -f stop_hook.handle_stop_hook_id handle_id"
+        self.interp.HandleCommand(command, result)
+        self.assertCommandReturn(result, "Added my command")
+
+        command = f"handle_id {current_stop_hook_id}"
+        self.interp.HandleCommand(command, result)
+        self.assertCommandReturn(result, "Registered my stop ID")
+
+        # Now step the process and make sure the stop hook was deleted.
+        thread.StepOver()
+        self.interp.HandleCommand("target stop-hook list", result)
+        self.assertEqual(result.GetOutput().rstrip(), "No stop hooks.", "Deleted hook")
+
     def test_stop_hooks_scripted(self):
         """Test that a scripted stop hook works with no specifiers"""
         self.stop_hooks_scripted(5, "-I false")

lldb/test/API/commands/target/stop-hooks/stop_hook.py

@@ -48,3 +48,28 @@ def handle_stop(self):
 class no_handle_stop:
     def __init__(self, target, extra_args, dict):
         print("I am okay")
+
+
+class self_deleting_stop:
+    def __init__(self, target, extra_args, dict):
+        self.target = target
+
+    def handle_stop(self, exe_ctx, stream):
+        interp = exe_ctx.target.debugger.GetCommandInterpreter()
+        result = lldb.SBCommandReturnObject()
+        interp.HandleCommand("handle_id", result)
+        id_str = result.GetOutput().rstrip()
+
+        command = f"target stop-hook delete {id_str}"
+        interp.HandleCommand(command, result)
+
+
+stop_hook_id = 0
+
+
+def handle_stop_hook_id(debugger, command, exe_ctx, result, extra_args):
+    global stop_hook_id
+    if command == "":
+        result.AppendMessage(str(stop_hook_id))
+    else:
+        stop_hook_id = int(command)