[MSVC] - Compiler option "/vd2"

[John Emmas <john creativepost co uk>]

This is the conversation that was previously named:-

    [Windows] Trash in sigc::trackable::callback_list_ when class is 
derived from Glib::Object

(mostly, a discussion between Marcin Kolny and myself).  After a bit of 
detective work we eventually concluded that where a programmer derives a 
class from Glib::Object (when building with MSVC) it's necessary to set 
the compiler flag "/vd2" during compilation. Marcin gave this simple 
example:-

class Test : public Glib::Object
{
public:
    Test()
    {
    }
};

When instantiating the above class, we could see that the member 
variable 'callback_list_' wasn't getting initialised correctly with most 
versions of MSVC.  Adding the flag '/vd2' fixed the problem.  I checked 
the higher level libraries (atkmm / gdkmm / pangomm / gtkmm) and 
discovered that all except for cairomm do indeed have this flag set 
during compilation.  So it seemed reasonable to apply it to my own 
programs (wherever they might declare objects derived from 
Glib::Object).  It certainly seemed to do the trick for the above example.

However...  I'm noticing that for more complex programs, the 'vd2' flag 
tends to cause strange runtime crashes - especially so in libsigc++ 
(remember that the variable 'callback_list_' is of type 
'sigc::trackable').  Currently I'm not building libsigc++ with the 
'/vd2' flag enabled.  Maybe I should be??  Is there any official advice 
regarding this for MSVC devs?  At the moment, adding that flag seems to 
have caused me a lot more problems than it solves... :-(

Thanks, John