gtknotebook-gtksocket_bug.cpp

# include <iostream>
# include <string>
# include <sstream>

# include <gtk/gtk.h>
# include <gdk/gdkkeysyms.h>

GtkWidget *mainWindow;
GtkWidget *tabBar;
GtkAccelGroup *hotkeys;

void pageAddedCallback(GtkNotebook *notebook, GtkWidget *child, guint pageNum)
{
	std::cerr<<"page added: "<<child<<" @ "<<pageNum<<std::endl;
}
void pageRemovedCallback(GtkNotebook *notebook, GtkWidget *child, guint pageNum)
{
	std::cerr<<"page removed: "<<child<<" @ "<<pageNum<<std::endl;
}
void plugAddedCallback(GtkSocket *socket)
{
	if(!GTK_IS_SOCKET(socket))
	{
		std::cerr<<"plugAddedCallback called with invalid socket: "<<socket<<std::endl;
		return;
	}
	std::cerr<<"plug added to "<<socket<<": "<<gtk_socket_get_plug_window(GTK_SOCKET(socket))<<" ("<<g_type_name(G_OBJECT_TYPE(gtk_socket_get_plug_window(GTK_SOCKET(socket))))<<")"<<std::endl;
}
gboolean plugRemovedCallback(GtkSocket *socket)
{
	if(!GTK_IS_SOCKET(socket))
	{
		std::cerr<<"plugRemovedCallback called with invalid socket: "<<socket<<std::endl;
		return true;
	}
	std::cerr<<"plug removed: "<<socket<<"|"<<gtk_socket_get_plug_window(GTK_SOCKET(socket))<<std::endl;

	return true;
}

void createNewTab()
{	
	GtkWidget *gtkSocket = gtk_socket_new();
	if(!(gtkSocket && GTK_IS_SOCKET(gtkSocket))) { return; }

	g_signal_connect(gtkSocket, "plug-added", G_CALLBACK(plugAddedCallback), NULL); 
	g_signal_connect(gtkSocket, "plug-removed", G_CALLBACK(plugRemovedCallback), NULL);

	int result = gtk_notebook_append_page(GTK_NOTEBOOK(tabBar), gtkSocket, NULL);
	if(result < 0)
	{
		std::cerr<<"failed to append page"<<std::endl;
		return;
	}
	gtk_widget_show(gtkSocket);
	gtk_notebook_set_current_page(GTK_NOTEBOOK(tabBar), -1);

	g_object_ref(G_OBJECT(gtkSocket));

	std::ostringstream conversionStream;
	conversionStream<<"view";
	conversionStream<<result;

	gtk_notebook_set_tab_label(GTK_NOTEBOOK(tabBar), gtkSocket, gtk_label_new(conversionStream.str().c_str()));

	std::cerr<<"created new tab "<<result<<std::endl;

	return;
}

int main(int argc, char **argv)
{
	gtk_init(&argc, &argv);
	if(!g_thread_supported())
	{
		g_thread_init(NULL);
	}

	mainWindow = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	tabBar = gtk_notebook_new();
	gtk_notebook_set_scrollable(GTK_NOTEBOOK(tabBar), TRUE);
	gtk_notebook_popup_enable(GTK_NOTEBOOK(tabBar));
	hotkeys = gtk_accel_group_new();
	gtk_accel_group_connect(hotkeys, GDK_T, GDK_CONTROL_MASK, GTK_ACCEL_VISIBLE, g_cclosure_new(GCallback(createNewTab), NULL, NULL));
	gtk_window_add_accel_group(GTK_WINDOW(mainWindow), hotkeys);

	gtk_container_add(GTK_CONTAINER(mainWindow), tabBar);
	createNewTab();

	g_signal_connect(tabBar, "page-added", G_CALLBACK(pageAddedCallback), NULL);
	g_signal_connect(tabBar, "page-removed", G_CALLBACK(pageRemovedCallback), NULL);

	gtk_widget_show_all(mainWindow);
	gtk_main();

	return 0;
}

How to use:
CTRL-T creates a new page.
Create many pages, at some point the terminal should start outputting a huge amount of alternating "page added..." and "plug removed..." messages.
E voila, the bug.