[boost] [container] Implemented Polymorphic Memory Resources

Subject: [boost] [container] Implemented Polymorphic Memory Resources
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2015-09-07 16:23:32

Hi to all,

In case anyone is interested, I just committed to the develop branch the 
implementation of the proposal "N3916 Polymorphic Memory Resources - r2" 
that was included in the TS "C++ Extensions for Library Fundamentals". 
The library continues to support C++03 compilers.

It basically introduces in namespace boost::container::pmr and the path 
boost/container/pmr/:

- memory_resource
- synchronized_pool_resource
- unsynchronized_pool_resource
- monotonic_buffer_resource
- polymorphic_allocator
- resource_adaptor
- new_delete_resource / null_memory_resource / get_default_resource / 
set_default_resource
- Aliases for all containers, using the polymorphic_allocator.

As default resource, new_delete_resource and null_memory_resource are 
required to be globals, they are implemented in the separately compiled 
boost.container library that was used to implement the DLMalloc-based 
extended allocator.

It seems that many users dislike building Boost libraries, but I felt 
this was the correct way to implement it. We could change or make it 
optionally header-only if there is demand. To avoid dependencies to some 
users, I made sure that memory_resource and resource_adaptor, which 
don't depend on the global default memory resource, can be used without 
linking the library.

Some logic was refactored from scoped_allocator_adaptor to avoid 
repeating the complicated template and preprocessor machinery in the 
polymorphic_allocator. I hope this does not cause any problem to scoped 
allocator users.

Any suggestion or bug report is welcome. Best,

Ion