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#### Class segmented

Boost.Context supports usage of a segmented, e. g. the size of the stack grows on demand. The coroutine is created with a minimal stack size and will be increased as required. Class segmented models the stack-allocator concept. In contrast to protected_fixedsize and fixedsize it creates a stack which grows on demand.

| Note
Segmented stacks are currently only supported by gcc from version 4.7 clang from version 3.4 onwards. In order to use a __segmented_stack__ Boost.Context must be built with toolset=gcc segmented-stacks=on at b2/bjam command-line. Applications must be compiled with compiler-flags -fsplit-stack -DBOOST_USE_SEGMENTED_STACKS.

    #include <boost/context/segmented.hpp>

    template< typename traitsT >
    struct basic_segmented
    {
        typedef traitT  traits_type;

        basic_segmented(std::size_t size = traits_type::default_size());

        stack_context allocate();

        void deallocate( stack_context &);
    }

    typedef basic_segmented< stack_traits > segmented;

###### `stack_context allocate()`

Preconditions:

  `traits_type::minimum:size() <= size` and `! traits_type::is_unbounded() && ( traits_type::maximum:size() >= size)`.

Effects:

  Allocates memory of at least `size` Bytes and stores a pointer to the stack and its actual size in `sctx`. Depending on the architecture (the stack grows downwards/upwards) the stored address is the highest/lowest address of the stack.

###### `void deallocate( stack_context & sctx)`

Preconditions:

  `sctx.sp` is valid, `traits_type::minimum:size() <= sctx.size` and `! traits_type::is_unbounded() && ( traits_type::maximum:size() >= sctx.size)`.

Effects:

  Deallocates the stack space.