Why is allocator::construct() called with one argument for '--std=c++0x'?

[Jonathan Wakely]

On 11 November 2011 00:54, Jonathan Wakely wrote:
> On 10 November 2011 23:49, Syncopated wrote:
>>
>> I'm using gcc 4.6.2. I tried to compile a program involving TBB 3.0 with the
>> following line and got a compilation error.
>>
>> vector<int, tbb::cache_aligned_allocator<int> > values(0);
>>
>> It turns out that  bits/stl_uninitialized.h is calling
>> allocator::construct() with only one argument, and
>> tbb::cache_aligned_allocator doesn't define it. AFAIK, construct() takes two
>> arguments. Is this something new in C++11, that construct() can take one
>> argument?
>
> Yes, the signature is now:
>
> template<class U, class... Args>
>  void construct(U* p, Args&&... args);
>
> So can take any number of arguments, which are passed on to the constructor.
>
> However in C++11 calls to allocators should be done through
> allcoator_traits, which abstracts the differences between C++03
> allocators and C++11 allocators, so it will work with allocators that
> only support the old 2-argument construct() signature.  Unfortunately
> we have only implemented allocator_traits in the unreleased GCC 4.7,
> i.e. the subversion trunk.
>
> In that code the code looks like this:
>  __traits::construct(__alloc, std::__addressof(*__cur));
> instead of
>  __alloc.construct(std::__addressof(*__cur));

I've opened a bug report for the problem in 4.6: http://gcc.gnu.org/PR51626