Minor simplification to the app handling

include/cactus_rt/thread.h

@@ -32,10 +32,6 @@ class Thread {
 
  std::atomic_bool stop_requested_ = false;
 
- // Non-owning App pointer. Used only for notifying that the thread has
- // started/stopped for tracing purposes.
- App* app_ = nullptr;
-
  pthread_t thread_;
  int64_t start_monotonic_time_ns_ = 0;
 
@@ -45,6 +41,21 @@ class Thread {
  */
  static void* RunThread(void* data);
 
+ friend class App;
+
+ // Non-owning App pointer. Used only for notifying that the thread has
+ // started/stopped for tracing purposes. Set by Thread::Start and read at
+ // the beginning of Thread::RunThread.
+ App* app_ = nullptr;
+
+ /**
+ * Starts the thread in the background.
+ *
+ * @param start_monotonic_time_ns should be the start time in nanoseconds for the monotonic clock.
+ * @param app The application that started this thread.
+ */
+ void Start(int64_t start_monotonic_time_ns, App* app);
+
  public:
  /**
  * Creates a new thread.
@@ -71,13 +82,6 @@ class Thread {
  */
  inline const std::string& Name() { return name_; }
 
- /**
- * Starts the thread in the background.
- *
- * @param start_monotonic_time_ns should be the start time in nanoseconds for the monotonic clock.
- */
- void Start(int64_t start_monotonic_time_ns);
-
  /**
  * Joins the thread.
  *
@@ -92,16 +96,6 @@ class Thread {
  stop_requested_ = true;
  }
 
- /**
- * @brief Sets the trace_aggregator_ pointer so the thread can notify the
- * trace_aggregator_ when it starts. This should only be called by App.
- *
- * @private
- */
- inline void SetApp(App* app) {
- app_ = app;
- }
-
  // The constructors and destructors are needed because we need to delete
  // objects of type Thread polymorphically, through the map in the App class.
  virtual ~Thread() = default;

src/cactus_rt/app.cc

@@ -15,7 +15,6 @@ using FileSink = cactus_rt::tracing::FileSink;
 namespace cactus_rt {
 
 void App::RegisterThread(std::shared_ptr<Thread> thread) {
- thread->SetApp(this);
  threads_.push_back(thread);
 }
 
@@ -44,7 +43,7 @@ void App::Start() {
 
  auto start_monotonic_time_ns = NowNs();
  for (auto& thread : threads_) {
- thread->Start(start_monotonic_time_ns);
+ thread->Start(start_monotonic_time_ns, this);
  }
 }
 

src/cactus_rt/thread.cc

@@ -30,8 +30,9 @@ void* Thread::RunThread(void* data) {
  return nullptr;
 }
 
-void Thread::Start(int64_t start_monotonic_time_ns) {
+void Thread::Start(int64_t start_monotonic_time_ns, App* app) {
  start_monotonic_time_ns_ = start_monotonic_time_ns;
+ app_ = app;
 
  pthread_attr_t attr;