Re: [boost] [config] request for BOOST_NO_FWD_STD_DECLARATION

Subject: Re: [boost] [config] request for BOOST_NO_FWD_STD_DECLARATION
From: Felipe Magno de Almeida (felipe.m.almeida_at_[hidden])
Date: 2011-02-22 09:30:36

On Tue, Feb 22, 2011 at 10:41 AM, Christopher Jefferson
<chris_at_[hidden]> wrote:
> On 22 Feb 2011, at 13:28, Felipe Magno de Almeida wrote:
>

[snip]

>> Isn't the standard library allowed to add template parameters with defaults?
>>
>> template <typename T, typename Allocator, typename _InternalParameter = int>
>> struct vector;
>
> No.

It seems Robert Steward agrees wit this.

> The fine details of the standard aren't really important here anyway. In practice there are compilers where we have been able to write well-defined forward declarations for many years and people have found them useful. On other standard libraries, like libc++, forward declarations are hard to write and not advised.
>
> Therefore we should support forward declarations where we can, and just include the standard headers where we can't.

It might be useful, but it is undefined behavior. I would hope boost
would depend as little as possible on undefined behavior.

> Chris

Regards,
-- 
Felipe Magno de Almeida