I am using glfw as part of my application. I recently ran Valgrind’s Memcheck which reports an invalid read.

Invalid read of size 4
    at 0x4C3DEF4: pthread_mutex_lock@@GLIBC_2.2.5 (pthread_mutex_lock.c:80)
    by 0x51DB32A: ??? (in /usr/lib/x86_64-linux-gnu/libwayland-client.so.0.22.0)
    by 0x51DB5DB: wl_display_dispatch_queue_pending (in /usr/lib/x86_64-linux-gnu/libwayland-client.so.0.22.0)
    by 0x171ABE: handleEvents (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x171978: _glfwPollEventsWayland (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x156B05: glfwPollEvents (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11EF64: Hamster::Window::Update(bool) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x119657: Hamster::Application::Run() (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x116EA0: main (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
  Address 0x4de7bb8 is 296 bytes inside a block of size 376 free'd
    at 0x484B27F: free (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
    by 0x16BFA4: _glfwTerminateWayland (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x14B6E6: terminate (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x14B7AD: glfwTerminate (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11EEB5: Hamster::Window::~Window() (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11AE8A: std::default_delete<Hamster::Window>::operator()(Hamster::Window*) const (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11ADAF: std::__uniq_ptr_impl<Hamster::Window, std::default_delete<Hamster::Window> >::reset(Hamster::Window*) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11A7BC: std::unique_ptr<Hamster::Window, std::default_delete<Hamster::Window> >::reset(Hamster::Window*) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x1198E4: Hamster::Application::Close(Hamster::WindowCloseEvent&) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x119D3F: Hamster::Application::Application()::$_0::operator()(Hamster::Event&) const (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x119D01: void std::__invoke_impl<void, Hamster::Application::Application()::$_0&, Hamster::Event&>(std::__invoke_other, Hamster::Application::Application()::$_0&, Hamster::Event&) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x119C91: std::enable_if<is_invocable_r_v<void, Hamster::Application::Application()::$_0&, Hamster::Event&>, void>::type std::__invoke_r<void, Hamster::Application::Application()::$_0&, Hamster::Event&>(Hamster::Application::Application()::$_0&, Hamster::Event&) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
  Block was alloc'd at
    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
    by 0x51DE0F3: wl_display_connect_to_fd (in /usr/lib/x86_64-linux-gnu/libwayland-client.so.0.22.0)
    by 0x51DE38D: wl_display_connect (in /usr/lib/x86_64-linux-gnu/libwayland-client.so.0.22.0)
    by 0x16A2E0: _glfwConnectWayland (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x152135: _glfwSelectPlatform (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x14B3ED: glfwInit (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11ECF9: Hamster::Window::Window(Hamster::WindowProps const&) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x11A478: std::_MakeUniq<Hamster::Window>::__single_object std::make_unique<Hamster::Window, Hamster::WindowProps&>(Hamster::WindowProps&) (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x118E48: Hamster::Application::Application() (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)
    by 0x116CE7: main (in /home/jaden/Documents/dev/Hamster/Hamster-App/Hamster-App)

A window is created when an application is created, the window is stored as a unique pointer as part of the application class. When glfw callsback for a window close, I handle it with Application::Close, which resets the unique pointer, destroying the window object. The main run loop is then shutdown.

Application.cpp

Application::Application() {
  WindowProps props;
  m_Window = std::make_unique<Window>(props);

  Renderer::Init(props.width, props.height);

  m_Dispatcher = std::make_unique<EventDispatcher>();

  m_Window->SetWindowEventDispatcher(m_Dispatcher.get());

  m_Dispatcher->Subscribe(
      WindowClose,
      FORWARD_CALLBACK_FUNCTION(Application::Close, WindowCloseEvent));

  glfwSetWindowCloseCallback(
      m_Window->GetGLFWWindowPointer(), [](GLFWwindow *windowGLFW) {
        EventDispatcher *dispatcher =
            (EventDispatcher *)glfwGetWindowUserPointer(windowGLFW);

        WindowCloseEvent e;

        dispatcher->Post<WindowCloseEvent>(e);
      });
}

Application::~Application() {
  std::cout << "Application destroyed" << std::endl;
}

void Application::Run() {
  while (m_running) {
    m_Window->Update(m_running);
  }
}

void Application::Close(WindowCloseEvent &e) {
  m_Window.reset();
  m_running = false;

  std::cout << "Application closed" << std::endl;
}

window.cpp

Window::Window(const WindowProps &props) {
  glfwInit();
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  GLFWwindow *window = glfwCreateWindow(props.width, props.height,
                                        props.title.c_str(), NULL, NULL);

  if (window == NULL) {
    std::cout << "Window creation failed" << std::endl;
  } else {
    s_NumWindows += 1;
  }

  m_Window = window;

  glfwMakeContextCurrent(window);
}

Window::~Window() {
  glfwDestroyWindow(m_Window);

  glfwTerminate();
}

void Window::Update(bool running) {
  glfwSwapBuffers(m_Window);

  glfwPollEvents();
}

The program compiles and executes with no errors. I suspect the error is in that during the glfwPollEvents() call, the window is destroyed, during the Window::Update call in Application.cpp, the window unique pointer is valid before glfwPollEvents() but not after (before the update scope exits). Given that this is a single threaded application, I’m stumped as to how this is happening.