Re: [MSVC] - Compiler option "/vd2"

[John Emmas <john creativepost co uk>]

Hi Marcin - you raised a couple of interesting points here:-

1st point:
On 07/09/2014 20:33, Marcin Kolny wrote:
> Could you tell us, what exactly problems have you met with /vd2 flag?

If I add the /vd2 flag to my own program (and rebuild, of course) the 
program runs fine but it crashes at shutdown.  The crash occurs at this 
code in '<libsigc++2>/sigc++/signal_base.h'

      struct SIGC_API signal_impl
      {

        //  some stuff

        inline void unreference()
          { if (!(--ref_count_)) delete this; }  // <--- CRASH OCCURS 
HERE !!

        //  some stuff
       };

I'm guessing there's some kind of problem with the 'this' pointer.  FWIW 
it makes no difference if I rebuild libsigc++ after adding the /vd2 
flag.  The only way I can avoid the crash is to NOT add /vd2, either to 
libsigc++ or to my own program code.


2nd point:
On 07/09/2014 20:33, Martin Kolny wrote:
> if you really would like to remove this flag, you have to know, that 
> you can't use dynamic_cast operator in your consturctors in that case. 
> (I don't know whether it's used somewhere in *mm projects or sigc++, 
> you have to check it).

What's interesting about this is the example code that you supplied 
originally.  AFAICT there wasn't any dynamic_cast operator getting used 
(either in your own c'tor - or Glib::Object's c'tor - or 
Glib::ObjectBases's c'tor - or anywhere in libsigc++).  And yet the 
constructed object was clearly not getting initialized properly.

So I'm wondering if it was just a happy accident that /vd2 fixed your 
original problem (since that wasn't an example of the kind of problem 
it's intended to fix).

Sadly, I'm still very mystified about what's going on here...  :-(

One thing of note though....  class Glib::ObjectBase is derived from 
sigc::trackable - but sigc::trackable seems to have a non-virtual 
d'tor.  I suppose that might be a factor in the crash that I'm seeing.  
I should probably look a bit deeper into this when I can find some time.

John