Re: [boost] [smart_ptr/static_pointer_cast] Trying to make ADL useful in my boost libraries

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2006-06-15 11:14:04

> Well, if foo<bar>(...) starts doing ADL it's going to break a lot of
> 
> code.  I certainly leave off qualification when using that notation,
> 
> knowing that ADL is avoided.

Ok. I see that in c.s.c++ there is a similar response. Revising 
shared_ptr and intrusive_ptr code I see that all the functions except 
for cast functions are adequate for ADL (operators + get_pointer()). 
This is a pity because this makes some pointer-independent code hard in 
Boost.

Interprocess/Shmem uses containers without supposing that 
allocator::pointer is a raw pointer and it uses static_pointer_cast to 
construct interprocess::list and interprocess:map classes avoiding 
template explosion. The current alternative would be:

smart_ptr -> get_pointer (ADL) -> raw pointer -> static_cast -> 
raw_pointer -> smart_ptr(raw_pointer)

Currently, I don't see any problem with this in Interprocess (obviously, 
this can be less efficient than having a specialized static cast 
function) but I think that we should have a new ADL-friendly cast 
mechanism in the smart_ptr library to write pointer independent code. 
These ADL-unfriendly cast functions make boost/pointer_cast.hpp useless 
in my opinion, as it was thought to be used for pointer independent code 
via ADL. And the alternatives like

    target = static_pointer_cast(source, (int*)0);

look pretty bad comparing to the original

    target = static_pointer_cast<int>(source);

Regards,

Ion