Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Allocator-aware constructor to create a polymorphic wrapper for the specified executor.

template<
    typename Executor,
    typename Allocator>
executor(
    allocator_arg_t ,
    const Allocator & a,
    Executor e);