unw_init_local man page
unw_init_local -- initialize cursor for local unwinding
int unw_init_local(unw_cursor_t *c, unw_context_t *ctxt);
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 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. From a behavioral point of view, the call:
ret = unw_init_local(&cursor, &ucontext);
is equivalent to:
ret = unw_init_remote(&cursor, unw_local_addr_space, &ucontext);
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.
On successful completion, unw_init_local() returns 0. Otherwise the negative value of one of the error-codes below is returned.
Thread and Signal Safety
unw_init_local() is thread-safe as well as safe to use from a signal handler.
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).
An unspecified error occurred.
A register needed by unw_init_local() wasn't accessible.
libunwind(3), unw_getcontext(3), unw_init_remote(3).