The unw_reg_states_iterate() routine provides information about the procedure that created the stack frame identified by argument cp. The cb argument is a pointer to a function of type unw_reg_states_callback which is used to return the information. The function unw_reg_states_callback has the following definition:
int ( *unw_reg_states_callback)(void *token, void *reg_states_data, size_t reg_states_data_size, unw_word_t start_ip, unw_word_t end_ip);
The callback function may be invoked several times for each call of unw_reg_states_iterate. Each call is associcated with a instruction address range and a set of instructions on how to update register values when returning from the procedure in that address range. For each invocation, the arguments to the callback function are:
On successful completion, unw_reg_states_iterate() returns 0. If the callback function returns a nonzero value, that indicates failure and the function returns immediately. Otherwise the negative value of one of the error-codes below is returned.
unw_reg_states_iterate() is thread-safe. If cursor cp is in the local address-space, this routine is also safe to use from a signal handler.