Re: [boost] shared_ptr extension with counter in object header

2003-02-23 Thread Thomas Witt 
Greg

On Sunday 23 February 2003 20:03, Greg Colvin wrote:
> At 03:34 AM 2/23/2003, Thomas Witt wrote:
> >Greg,
> >
> >I can not figure out how you make sure to satisfy the alignment
> > constraints of T and counted_base_header_impl. Any hint would be
> > appreciated.
>
> I just used two char arrays, thinking there was a dispensation
> somewhere in the standard to allow for placement new into char
> arrays:

Yep, you are right its 5.3.4/10. I missed it.

Thomas

-- 
Dipl.-Ing. Thomas Witt
Institut fuer Verkehrswesen, Eisenbahnbau und -betrieb, Universitaet Hannover
voice: +49(0) 511 762 - 4273, fax: +49(0) 511 762-3001
http://www.ive.uni-hannover.de

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Re: [boost] shared_ptr extension with counter in object header

2003-02-23 Thread Greg Colvin 
At 03:34 AM 2/23/2003, Thomas Witt wrote:

>Greg,
>
>I can not figure out how you make sure to satisfy the alignment constraints of 
>T and counted_base_header_impl. Any hint would be appreciated.

I just used two char arrays, thinking there was a dispensation
somewhere in the standard to allow for placement new into char
arrays:

   template struct object_with_counted_header {
  char header[sizeof(counted_base_header_impl >)];
  char object[sizeof(T)];
   };

If I'm wrong, an alternative might be:

   template struct object_with_counted_header {
  counted_base_header_impl > header;
  T object;
   };

But then you can't use offsetof, and some fancier tricks will
be in order.

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Re: [boost] shared_ptr extension with counter in object header

2003-02-23 Thread Thomas Witt 

Greg,

I can not figure out how you make sure to satisfy the alignment constraints of 
T and counted_base_header_impl. Any hint would be appreciated.

Thanks

Thomas


-- 
Dipl.-Ing. Thomas Witt
Institut fuer Verkehrswesen, Eisenbahnbau und -betrieb, Universitaet Hannover
voice: +49(0) 511 762 - 4273, fax: +49(0) 511 762-3001
http://www.ive.uni-hannover.de

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