The <ucontext.h> header defines the ucontext_t type as a structure that includes at least the following members:
ucontext_t uc_link sigset_t uc_sigmask stack_t uc_stack mcontext_t uc_mcontext
The uc_link member is a pointer to the context to be resumed when this context returns. If uc_link is equal to 0, this context is the main context and the process exits when this context returns.
The uc_sigmask member defines the set of signals that are blocked when this context is active. See sigprocmask(2).
The uc_stack member defines the stack used by this context. See sigaltstack(2).
The uc_mcontext member contains the saved set of machine registers and any implementation-specific context data. Portable applications should not modify or access uc_mcontext.
See attributes(5) for descriptions of the following attributes: