[boost] Re: compressed_pair requirements?

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2005-06-03 21:47:48

On Jun 3, 2005, at 1:23 PM, David Abrahams wrote:

> Okay, here's your next challenge.  This is with the very latest Comeau
> alpha release compiler.
>
> "c:\boost/boost/type_traits/is_member_function_pointer.hpp", line 67: 
> warning #1290-D:
>           non-POD class type passed through ellipsis

That's ominous!  This is exactly what I was talking about when:

On May 26, 2005, at 9:02 AM, Howard Hinnant wrote:

> I haven't dug into boost::is_pointer, but I'm guessing it involves a 
> tentative binding to an ellipsis:
>
>     template <class U> static two  test(...);
>
> 5.2.2p7 says that binding a non-POD class type to an ellipsis has 
> undefined behavior.  CodeWarrior's behavior in this context is to try 
> to pass the type by value by using the type's copy constructor, which 
> in this case is private, and thus triggers the access error.

The scary part is that we do so many useful things these days by 
tentatively passing non-POD's past an ellipses, though only at compile 
time, never at run time.  But the compiler is not making that 
distinction.

This is a big problem, and I suspect it will need to be addressed at 
the standards level.  I don't have a solution yet.

-Howard