Re: [Boost-users] [interprocess] access dynamically accessed shared region in another process

Subject: Re: [Boost-users] [interprocess] access dynamically accessed shared region in another process
From: Stephan Menzel (stephan.menzel_at_[hidden])
Date: 2009-04-01 14:40:11

Am Mittwoch, 1. April 2009 18:58:39 schrieb Ion Gaztañaga:
>
> Thanks for the quick reply, Dan. Yes, all pointers placed in shared
> memory should be offset_ptr as explained here:
>
> http://www.boost.org/doc/libs/1_38_0/doc/html/interprocess/sharedmemorybetw
>eenprocesses.html#interprocess.sharedmemorybetweenprocesses.mapped_region_ob
>ject_limitations

Thanks for the quick reply!
Meanwhile I suspected as much, but didn't know for sure how to interpret the 
docs. 
Also, this alignment check taken from the docs doesn't compile anymore with a 
pointer type as such:

struct transfer_buffer {
   boost::interprocess::offset_ptr<void>   buf; 
   size_t                                  bufsize; 
};
...
ret->bufsize = SIZE;
ret->buf = seg->allocate_aligned(ret->bufsize, Alignment);

// Check alignment
assert((static_cast<void *>(ret->buf) - static_cast<void *>(0)) % Alignment == 
0);

The assert gives me:
/home/sm/devel/rtssvn/cpp/librender/Render.cpp:109: Erro: invalid static_cast 
of type »boost::interprocess::offset_ptr<void>« into type »void*«

Is that assert actually neccessary? I wouldn't know what to do in case of a 
failure anyway.... Performance accessing the buffer matters a lot though.

Cheers,

Stephan