[boost] Re: call_traits<int&>::value_type

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2003-03-20 18:06:41

On Thursday, March 20, 2003, at 05:17  PM, Eric Niebler wrote:

> It's not a compiler thing.  Look at the implementation:
>
> http://www.boost.org/boost/detail/call_traits.hpp
>
> template <typename T>
> struct call_traits<T&>
> {
>    typedef T& value_type; // <-- problem here
>    typedef T& reference;
>    typedef const T& const_reference;
>    typedef T& param_type;  // hh removed const
> };

Fwiw, I put a version of call_traits into the Metrowerks::lib a couple 
of years ago when it was first developed on boost.  At that time I gave 
call_traits<int&>::value_type the type of int.  I also built code based 
on that assumption that looks not too different from what Eric posted:

template<class T, class Allocator = single_deleter<T>,
        class Size = number<typename 
call_traits<Allocator>::value_type::size_type, 1> >
        class alloc_ptr;

In this class, the Allocator type may be a reference to an allocator 
instead of an allocator (and that is a valuable feature I use).  
Indeed, that is why I used call_traits here in the first place.  In 
retrospect, using remove_reference instead of call_traits here would 
probably be a better choice...

-Howard