[eigen] [Pool] Problems using Boost.Pool with the Eigen matrix library

[lfrfly@xxxxxxxxxxx]

Since Eigen matrices and vectors use SSE and therefore require a 
particular alignment, Eigen requires that when these types 
(specifically, the compile-time sized versions) are within a struct or 
class, that struct be given the EIGEN_MAKE_ALIGNED_OPERATOR_NEW macro.

But here's the problem. What if that struct is allocated by a 
boost::pool_allocator<T>? Is there any way to enforce alignment then? 
I'm trying it and it just isn't working. I keep getting breakpoints hit 
inside of Eigen calls, presumably due to unaligned accesses.

Has anyone investigated this, and are there any reasonable options? 
Perhaps a way to force the pool's start to be aligned, and a way to 
make sure the sizeof() my type as a whole is aligned? (But what about 
allocator conversion, eg, std::allocate_shared<T> may take an 
allocator<T> but it converts it internally to an 
allocator<somewrapper<T>>?)