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Boost.Coroutine supports usage of a segmented-stack, 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_stack_allocator models the stack-allocator concept. In contrast to protected_stack_allocator and standard_stack_allocator it creates a stack which grows on demand.
| ![[Note]](../../../../../../doc/src/images/note.png) | Note | 
|---|---|
| Segmented stacks are currently only supported by gcc from version 4.7 and clang from version 3.4 onwards. In order to use a segmented-stack Boost.Coroutine 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/coroutine/segmented_stack_allocator.hpp> template< typename traitsT > struct basic_segmented_stack_allocator { typedef traitT traits_type; void allocate( stack_context &, std::size_t size); void deallocate( stack_context &); } typedef basic_segmented_stack_allocator< stack_traits > segmented_stack_allocator;
void allocate( stack_context
        & sctx, std::size_t size)
      
              traits_type::minimum_size()
              <= size
              and ! traits_type::is_unbounded() &&
              ( traits_type::maximum_size() >= size).
            
              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)
      
              sctx.sp is valid, traits_type::minimum_size() <= sctx.size and !
              traits_type::is_unbounded()
              && (
              traits_type::maximum_size()
              >= sctx.size).
            
Deallocates the stack space.