Re: [boost] Re: Constructor-proxy: Template parameter deduction, a question for template masters

From: Ion Gaztañaga (ion_g_m_at_[hidden])
Date: 2005-02-19 06:36:04

Hello Pavel,

>> T * ptr = shmem_segment.create<T>("ObjectName")[size]
>
> It could be then used:
>
> T* t = segment.create(...); // no smarteness used
> shmem_smart_pointer ptr = segment_create(...); // smart ptr used
> (void)segment.create(...); // no leak happens

The shared memory allocation is done in the proxy function, the example I've 
put was just to see the const_ref-non_const-ref problem so

T* t = segment.create<T>("name"); -->

T* t = segment.create<T>("name")/*proxy object returned*/; -->

Is an invalid option and it does not compile, because that expresion returns 
a temporary proxy object not assignable to T*. To build an object without 
parameters, you should do:

T* t = segment.create<T>("name")( ); -->

T* t = segment.create<T>("name") /*proxy object returned, calling to 
operator()*/
                                       ( /*empty param list*/); /*pointer 
returned*/

because the argument-less operator() is the responsible for allocating _and_ 
constructing the object, so there are no leaks. Obviously, this syntax is 
not very straight forward, and I should try to get more logical syntax when 
default constructing objects:

T* t = segment.create<T>("name");

I will have a look at it, since I think this syntax is better, thank you for 
the idea. Regarding to const/non_const parameter issue, I will try to make a 
simpler example not involving proxies to just point out the problem and 
repost the question hoping there is response.

Meanwhile, I keep on improving Shmem, currently adding boost unordered _map 
as name/memory mapping association instead of assoc_vector to test 
pros/cons.

Regards,

 /Ion>