Re: gtkmm2.4 and MSVC (again)

[Cedric Gustin <cedric gustin swing be>]

m h wrote:

> window1_glade::window1_glade():Gtk::Window(Gtk::WINDOW_TOPLEVEL){
>
> Gtk::Window * window1 = this;
> try {
>
> Gtk::Widget * q = dynamic_cast<Gtk::Widget *>(
>   Glib::ObjectBase::_get_current_wrapper((GObject
> *)(window1->gobj())));
>
> }
>
> (this line is from Widget_class::show_callback().  i'm
> not sure why this cast fails when a derived class has
> member variables.  any idea why this matters?

I guess this problem is beyond my gtkmm/C++/MSVC expertize.

I worked on this simple helloworld example

----- Cut here -----

#include <gtkmm/main.h>
#include <gtkmm/button.h>
#include <gtkmm/window.h>

class HelloWorld : public Gtk::Window
{
public:
	HelloWorld();
	virtual ~HelloWorld() {}

protected:
  Gtk::Button m_button;
};

class MyHelloWorld : public HelloWorld
{
public:
	MyHelloWorld() {}
	virtual ~MyHelloWorld() {}

private:
	int i;  // comment this out and helloworld does not crash !
};

HelloWorld::HelloWorld()
: m_button("Hello World")
{
  // helloworld crashes here if MyHelloWorld has the integermember
  // Stepping into add(m_button),
  // gtk_container_add(this->gobj(),m_button.gobj())
  // is supposed to be called. this->gobj() and m_button.gobj() return
  // correctly but the call to gtk_container_add results in a coredump
  // (objectbase.cc) in the ObjectBase::is_derived_ method !!!
  add(m_button);
  m_button.show();
}

int main (int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  MyHelloWorld helloworld;
  Gtk::Main::run(helloworld);

  return 0;
}

----- cut here -----

As pointed ou by Matt, there is a problem when a member (int i) is added 
 to a derived class. helloworld crashes at the add(m_button) line, 
which corresponds to a gtk_container_add call (Timothy also pointed out 
this bottleneck). For some unknown reason, the program then jumps to the 
ObjectBase::is_derived_ method and crashes. Comment out the "int i;" 
declaration, and it works as expected.

By the way, I also reproduced the crash against a native MSVC build of 
GTK+ (http://severna.homeip.net/gtk-win32.php)

I'm lost...

Cedric