unw_init_local -- initialize cursor for local unwinding

       David Mosberger-Tang
       Email: dmosberger@gmail.com
       WWW: http://www.nongnu.org/libunwind/.

Programming Library                              16 August 2017                                UNW_INIT_LOCAL(3)

       The  unw_init_local() routine initializes the unwind cursor pointed to by c with the machine-state in the
       context structure pointed to by ctxt.  As such, the machine-state  pointed  to  by  ctxt  identifies  the
       initial stack frame at which unwinding starts. The machine-state is expected to be one provided by a call
       to  unw_getcontext;  as  such,  the  instruction  pointer  may  point  to  the instruction after the last
       instruction of a function, and libunwind will back-up the instruction pointer before beginning a walk  up
       the call stack. The machine-state must remain valid for the duration for which the cursor c is in use.

       The  unw_init_local()  routine can be used only for unwinding in the address space of the current process
       (i.e., for local unwinding).  For all other cases, unw_init_remote()  must  be  used  instead.   However,
       unwind  performance  may be better when using unw_init_local().  Also, unw_init_local() is available even
       when UNW_LOCAL_ONLY has been defined before including <libunwind.h>, whereas unw_init_remote() is not.

       If the unw_context_t is known to be a signal frame (i.e., from the third argument in a sigaction  handler
       on  linux),  unw_init_local2()  should  be used for correct initialization on some platforms, passing the
       UNW_INIT_SIGNAL_FRAME flag.

       UNW_EINVAL
               unw_init_local()  was called in a version of libunwind which supports remote unwinding only (this
              normally happens when calling unw_init_local() for a cross-platform version of libunwind).

       UNW_EUNSPEC
               An unspecified error occurred.

       UNW_EBADREG
               A register needed by unw_init_local() wasn't accessible.

       unw_init_local -- initialize cursor for local unwinding

       On successful completion, unw_init_local() returns 0.   Otherwise  the  negative  value  of  one  of  the
       error-codes below is returned.

libunwind(3), unw_init_remote(3)

       #include <libunwind.h>

       int unw_init_local(unw_cursor_t *c, unw_context_t *ctxt);
       int unw_init_local2(unw_cursor_t *c, unw_context_t *ctxt, int flag);

       unw_init_local() is thread-safe as well as safe to use from a signal handler.