Re: [Boost-users] Serialization: C4308 warning with MSVC9

19 May 2010

      --- On Tue, 5/18/10, Robert Ramey  wrote:
...
...
--- On Tue, 5/18/10, Robert Ramey 
wrote:
...
From: Robert Ramey 
Subject: Re: [Boost-users] Serialization: C4308
warning with MSVC9
To: boost-users@lists.boost.org
Date: Tuesday, May 18, 2010, 10:35 PM
Political Confusion wrote:
...
Political Confusion  writes:
...
I'm using Boost 1.43 with MSVC9 SP1 and
Windows
SDK v7 on Windows 7.
...
I've
created a class like the "A Very
Simple Case" example (i.e. added 'access'
as
friend and a templated
serialize function). In serialize, I just
archive 10 ints (signed
and unsigned). It compiles fine, but when
I add program code to
save my class to a text_oarchive, I get a
warning:
c:\third-party\boost_1_43_0\boost\mpl\print.hpp(51) :
...
warning C4308:
...
...
negative integral constant converted to
unsigned
type
Line 51 of print.hpp is: enum { n =
sizeof(T) + -1
};
Calling sizeof() on my class gives a 44.
I
do not get any warning
when I load
my class with text_iarchive. And
both save and load appear to work fine.
I had to add the following to make this
warning go
away:
BOOST_CLASS_TRACKING( my_class,
boost::serialization::track_never )
This warning should precede a long call chain. If
you
go to the the
call BEFORE this, you should find a comment which
indicates
why this
warning is invoked.
Robert Ramey
_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
http://lists.boost.org/mailman/listinfo.cgi/boost-users
Hello Robert,
That's what I did.  The lines above the warning
(boost/archive/detail/check.hpp(98)):
     // saving an non-const object
of a type not marked "track_never)
     // may be an indicator of an
error usage of the
     // serialization library and
should be double checked.
     // See documentation on object
From: Robert Ramey 
Subject: Re: [Boost-users] Serialization: C4308 warning with MSVC9
To: boost-users@lists.boost.org
Date: Tuesday, May 18, 2010, 11:57 PM
Political Confusion wrote:
tracking.  Also, see the
...
     // "rationale" section of the
documenation
     // for motivation for this
checking.

   BOOST_STATIC_WARNING(typex::value);
...
So I added the BOOST_CLASS_TRACKING() line.  I
get the same warning
...
if I modify save_schedule() in demo.cpp to instantiate
a gps_position
and save it to oa.  gps_position was the example
I used for my class.
Thanks for the reply and thanks for your work.
But this begs the real question.  Do you want tracking
or don't you.
Without tracking -
     you won't be able to serialize
apointer.
    and you'll missing the opptimization of space
if the same object is 
serialized more than once.
    It will be faster to save and restore
With tracking
    The opposite will be true
So the decision to use tracking shouldn't made  as to
the easiest way to fix 
the warning.
The other way is to make the object we're saving
non-const.
Robert Ramey
_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
http://lists.boost.org/mailman/listinfo.cgi/boost-users
I don't think I need tracking, but I can't say for sure.  This is my class:

   class WindowPlacement : public WINDOWPLACEMENT
   {
   public:

      WindowPlacement() { length = sizeof( WINDOWPLACEMENT ); }

   private:

      friend class se::access;

      template < typename Archive >
      void serialize( Archive& ar, const unsigned int version )
      {
         ar & flags;
         ar & showCmd;
         ar & ptMinPosition.x;
         ar & ptMinPosition.y;
         ar & ptMaxPosition.x;
         ar & ptMaxPosition.y;
         ar & rcNormalPosition.left;
         ar & rcNormalPosition.top;
         ar & rcNormalPosition.right;
         ar & rcNormalPosition.bottom;
      }
   };

I load it to an object declared on the stack when my main window is created.  I save it from a stack object before my main window is destroyed.  In case you don't know, WINDOWPLACEMENT is a struct defined by Microsoft:

   typedef struct tagWINDOWPLACEMENT {     /* wndpl */
      UINT length;
      UINT flags;
      UINT showCmd;
      POINT ptMinPosition;
      POINT ptMaxPosition;
      RECT rcNormalPosition;
   } WINDOWPLACEMENT;

I don't understand "The other way is to make the object we're saving non-const."  My instantiated class has to be non-const in order to pass it to GetWindowPlacement/SetWindowPlacement of the Windows API.

Thanks for your time,

Michael