_Alloc_hider?

[Jonathan Wakely]

On 16 August 2011 01:13, Jeffrey Walton wrote:
> On Mon, Aug 15, 2011 at 7:48 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> On 16 August 2011 00:43, Jonathan Wakely wrote:
>>> On 16 August 2011 00:30, Jeffrey Walton wrote:
>>>> Hi All,
>>>>
>>>> I'm testing a custom allocator. The allocator works well with vector,
>>>> but fails to link with basic_string (see below).
>>>>
>>>> I looked through Stroustrup and could not find info on _Alloc_hider.
>>>
>>> It starts with an underscore followed by an upper case letter, so it's
>>> in the implementation namespace i.e. it's an implementation detail, so
>>> you're not going to find it in a book.
> I thought it might have been a GCC extension that might have leaked to
> the surface. It happens on occasion, especially with less frequently
> used stuff.

You still wouldn't find it in Stroustrup though :)

Looking in the source file giving the error would have told you the
answer, as it's commented, with a link explaining the EBO.

>>>
>>>> Searching online doesn't reveal much either (perhaps I have not waded
>>>> through enough irrelevant fodder). I did find [1], buts its just
>>>> DoOxygen with no real content (its written in STL terseness with no
>>>> comments).
>>>>
>>>> I believe I need another constructor, but I'm not sure what it takes
>>>> or how to write it:
>>>>
>>>>  inline explicit zallocator() { }
>>>>  inline ~zallocator() { }
>>>>  inline explicit zallocator(zallocator const&) { }
>>>>
>>>>  template<typename U>
>>>>  inline explicit zallocator(zallocator<U> const&) { }
>>>>
>>>> How does one one provided an allocator for use by a basic_string?
>>>
>>> By writing a type that meets the C++03 Allocator requirements, which
>>> yours doesn't.
> For what its worth, I did not spicy -std=XXX.

Doesn't matter, the libstdc++ std::string only supports C++03
allocators, so you have to meet those requirements.  At some point
I'll make the changes to support the slightly different C++11
allocator model in c++0x mode, but that's not done yet.