Re: [boost] [smart_ptr] !defined(BOOST_NO_CXX11_SMART_PTR) does notimply !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)

Subject: Re: [boost] [smart_ptr] !defined(BOOST_NO_CXX11_SMART_PTR) does notimply !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
From: Michel Morin (mimomorin_at_[hidden])
Date: 2013-02-08 23:22:06

Peter Dimov wrote:
> Michel Morin wrote:
>
>> `!defined(BOOST_NO_CXX11_SMART_PTR)` does not necessarily mean that
>> the compiler support of rvalue references is available. For example,
>
>
> How could the standard library have std::unique_ptr without the compiler
> supporting rvalue references?

Seems like libc++ uses rvalue-ref emulation:
  http://llvm.org/svn/llvm-project/libcxx/trunk/include/memory

>> when I use shared_ptr (on trunk) with clang + libc++ in a C++03 mode,
>> I get warnings something like
>>
>>   boost/smart_ptr/shared_ptr.hpp:556:51:
>>   warning: rvalue references are a C++11 extension [-Wc++11-extensions]
>>     shared_ptr & operator=( std::unique_ptr<Y, D> && r )
>
>
> Looks like rvalue references are available, but as an extension.

You're right. But compiling with -Werror or -pedantic-errors results in
compilation errors. Also BOOST_NO_CXX11_RVALUE_REFERENCES is defined.

Regards,
Michel