Add a new SBDebugger::SetDestroyCallback() API

Adding a new SBDebugger::SetDestroyCallback() API.
This API can be used by any client to query for statistics/metrics before
exiting debug sessions.

Differential Revision: https://reviews.llvm.org/D143520

Author: Jeffrey Tan

lldb/bindings/python/python-typemaps.swig

@@ -384,6 +384,29 @@ template <> bool SetNumberFromPyObject<double>(double &number, PyObject *obj) {
   $1 = $1 || PyCallable_Check(reinterpret_cast<PyObject *>($input));
 }
 
+// For lldb::SBDebuggerDestroyCallback
+%typemap(in) (lldb::SBDebuggerDestroyCallback destroy_callback, void *baton) {
+  if (!($input == Py_None ||
+        PyCallable_Check(reinterpret_cast<PyObject *>($input)))) {
+    PyErr_SetString(PyExc_TypeError, "Need a callable object or None!");
+    SWIG_fail;
+  }
+
+  // FIXME (filcab): We can't currently check if our callback is already
+  // LLDBSwigPythonCallPythonSBDebuggerTerminateCallback (to DECREF the previous
+  // baton) nor can we just remove all traces of a callback, if we want to
+  // revert to a file logging mechanism.
+
+  // Don't lose the callback reference
+  Py_INCREF($input);
+  $1 = LLDBSwigPythonCallPythonSBDebuggerTerminateCallback;
+  $2 = $input;
+}
+
+%typemap(typecheck) (lldb::SBDebuggerDestroyCallback destroy_callback, void *baton) {
+  $1 = $input == Py_None;
+  $1 = $1 || PyCallable_Check(reinterpret_cast<PyObject *>($input));
+}
 
 %typemap(in) lldb::FileSP {
   PythonFile py_file(PyRefType::Borrowed, $input);

lldb/bindings/python/python-wrapper.swig

@@ -1106,4 +1106,16 @@ static void LLDBSwigPythonCallPythonLogOutputCallback(const char *str,
     SWIG_PYTHON_THREAD_END_BLOCK;
   }
 }
+
+// For DebuggerTerminateCallback functions
+static void LLDBSwigPythonCallPythonSBDebuggerTerminateCallback(lldb::user_id_t debugger_id,
+                                                      void *baton) {
+  if (baton != Py_None) {
+    SWIG_PYTHON_THREAD_BEGIN_BLOCK;
+    PyObject *result = PyObject_CallFunction(
+        reinterpret_cast<PyObject *>(baton), const_cast<char *>("l"), debugger_id);
+    Py_XDECREF(result);
+    SWIG_PYTHON_THREAD_END_BLOCK;
+  }
+}
 %}

lldb/include/lldb/API/SBDefines.h

@@ -122,6 +122,10 @@ class LLDB_API SBUnixSignals;
 typedef bool (*SBBreakpointHitCallback)(void *baton, SBProcess &process,
                                         SBThread &thread,
                                         lldb::SBBreakpointLocation &location);
+
+typedef void (*SBDebuggerDestroyCallback)(lldb::user_id_t debugger_id,
+                                          void *baton);
+
 typedef void *ScriptedObject;
 }
 

lldb/include/lldb/Core/Debugger.h

@@ -479,6 +479,10 @@ class Debugger : public std::enable_shared_from_this<Debugger>,
 
   static void ReportSymbolChange(const ModuleSpec &module_spec);
 
+  void
+  SetDestroyCallback(lldb_private::DebuggerDestroyCallback destroy_callback,
+                     void *baton);
+
 protected:
   friend class CommandInterpreter;
   friend class SwiftREPL;
@@ -524,6 +528,8 @@ class Debugger : public std::enable_shared_from_this<Debugger>,
                                    llvm::Optional<lldb::user_id_t> debugger_id,
                                    std::once_flag *once);
 
+  void HandleDestroyCallback();
+
   void PrintProgress(const ProgressEventData &data);
 
   bool StartEventHandlerThread();
@@ -627,6 +633,9 @@ class Debugger : public std::enable_shared_from_this<Debugger>,
   llvm::once_flag m_clear_once;
   lldb::TargetSP m_dummy_target_sp;
 
+  lldb_private::DebuggerDestroyCallback m_destroy_callback = nullptr;
+  void *m_destroy_callback_baton = nullptr;
+
   uint32_t m_interrupt_requested = 0; ///< Tracks interrupt requests
   std::mutex m_interrupt_mutex;
 

lldb/include/lldb/lldb-private-types.h

@@ -112,6 +112,8 @@ typedef struct type256 { uint64_t x[4]; } type256;
 using ValueObjectProviderTy =
     std::function<lldb::ValueObjectSP(ConstString, StackFrame *)>;
 
+typedef void (*DebuggerDestroyCallback)(lldb::user_id_t debugger_id,
+                                        void *baton);
 } // namespace lldb_private
 
 #endif // #if defined(__cplusplus)

lldb/source/API/SBDebugger.cpp

@@ -1684,6 +1684,15 @@ void SBDebugger::SetLoggingCallback(lldb::LogOutputCallback log_callback,
   }
 }
 
+void SBDebugger::SetDestroyCallback(
+    lldb::SBDebuggerDestroyCallback destroy_callback, void *baton) {
+  LLDB_INSTRUMENT_VA(this, destroy_callback, baton);
+  if (m_opaque_sp) {
+    return m_opaque_sp->SetDestroyCallback(
+        destroy_callback, baton);
+  }
+}
+
 SBTrace
 SBDebugger::LoadTraceFromFile(SBError &error,
                               const SBFileSpec &trace_description_file) {

lldb/source/Core/Debugger.cpp

@@ -559,6 +559,12 @@ void Debugger::Terminate() {
   assert(g_debugger_list_ptr &&
          "Debugger::Terminate called without a matching Debugger::Initialize!");
 
+  if (g_debugger_list_ptr && g_debugger_list_mutex_ptr) {
+    std::lock_guard<std::recursive_mutex> guard(*g_debugger_list_mutex_ptr);
+    for (const auto &debugger : *g_debugger_list_ptr)
+      debugger->HandleDestroyCallback();
+  }
+
   if (g_thread_pool) {
     // The destructor will wait for all the threads to complete.
     delete g_thread_pool;
@@ -678,10 +684,18 @@ DebuggerSP Debugger::CreateInstance(lldb::LogOutputCallback log_callback,
   return debugger_sp;
 }
 
+void Debugger::HandleDestroyCallback() {
+  if (m_destroy_callback) {
+    m_destroy_callback(GetID(), m_destroy_callback_baton);
+    m_destroy_callback = nullptr;
+  }
+}
+
 void Debugger::Destroy(DebuggerSP &debugger_sp) {
   if (!debugger_sp)
     return;
 
+  debugger_sp->HandleDestroyCallback();
   CommandInterpreter &cmd_interpreter = debugger_sp->GetCommandInterpreter();
 
   if (cmd_interpreter.GetSaveSessionOnQuit()) {
@@ -1346,6 +1360,12 @@ void Debugger::SetLoggingCallback(lldb::LogOutputCallback log_callback,
       std::make_shared<CallbackLogHandler>(log_callback, baton);
 }
 
+void Debugger::SetDestroyCallback(
+    lldb_private::DebuggerDestroyCallback destroy_callback, void *baton) {
+  m_destroy_callback = destroy_callback;
+  m_destroy_callback_baton = baton;
+}
+
 static void PrivateReportProgress(Debugger &debugger, uint64_t progress_id,
                                   std::string title, std::string details,
                                   uint64_t completed, uint64_t total,

lldb/test/API/python_api/debugger/TestDebuggerAPI.py

@@ -147,3 +147,17 @@ def test_CreateTarget_arch(self):
             platform2.GetWorkingDirectory().endswith("bar"),
             platform2.GetWorkingDirectory(),
         )
+
+    def test_SetDestroyCallback(self):
+        destroy_dbg_id = None
+
+        def foo(dbg_id):
+            # Need nonlocal to modify closure variable.
+            nonlocal destroy_dbg_id
+            destroy_dbg_id = dbg_id
+
+        self.dbg.SetDestroyCallback(foo)
+
+        original_dbg_id = self.dbg.GetID()
+        self.dbg.Destroy(self.dbg)
+        self.assertEqual(destroy_dbg_id, original_dbg_id)