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The implementation uses fcontext_t per default. fcontext_t is based on assembler and not available for all platforms. It provides a much better performance than ucontext_t (the context switch takes two magnitudes of order less CPU cycles) and WinFiber.
        As an alternative, ucontext_t
        can be used by compiling with BOOST_USE_UCONTEXT
        and b2 property context-impl=ucontext.
        ucontext_t might be available on a broader range of
        POSIX-platforms but has some (for instance deprecated since POSIX.1-2003,
        not C99 conform).
      
| ![[Note]](../../../../../../doc/src/images/note.png) | Note | 
|---|---|
| call/cc supports Segmented stacks only with ucontext_t as its implementation. | 
        With BOOST_USE_WINFIB and
        b2 property context-impl=winfib
        Win32-Fibers are used as implementation for call/cc.
      
Because the TIB (thread information block) is not fully described in the MSDN, it might be possible that not all required TIB-parts are swapped.
| ![[Note]](../../../../../../doc/src/images/note.png) | Note | 
|---|---|
| 
          The first call of call/cc converts the thread into
          a Windows fiber by invoking  |