Subject: Re: [boost] [config] std::unique_ptr, std::ref detection?
From: Daniel James (dnljms_at_[hidden])
Date: 2012-03-03 07:51:27
On 1 March 2012 23:34, Jeffrey Lee Hellrung, Jr.
<jeffrey.hellrung_at_[hidden]> wrote:
>
> I think the important distinction is
>
> "BOOST_NO_INITIALIZER_LISTS is probably useless as
> it only indicates compiler support and initializer lists can't really
> be used without the header."
>
> I wasn't sure whether initializer lists required a header, so I agree with
> Daniel that it's probably redundant.
I was wrong, C++11 added other uses which don't require the header.
Although I don't think portable code would ever need to take advantage
of that.
The situation with the visual c++ 10 beta was that initializer lists
weren't supported, but the header was present. In that case
BOOST_NO_INITIALIZER_LISTS would be defined, but
BOOST_NO_0X_HDR_INITIALIZER_LISTS would not. A compiled library might
still want to define methods which take initializer lists so that they
can be used when linking with a different compiler that does support
them.
If you look at unordered, it now uses
BOOST_NO_0X_HDR_INITIALIZER_LISTS in the headers (they support
std::initializer_list but don't ever create one), but
BOOST_NO_INITIALIZER_LISTS for test cases that actually use an
initializer list.
But.... it looks like including the header in Visual C++ 10 was
actually a mistake:
It's also confusing having the two macros, very easy to get wrong, and
the potential use cases are pretty dubious.