rb_vm_backtrace_str_ary 4854 thread.c       VALUE rb_vm_backtrace_str_ary(rb_thread_t *th, long lev, long n);
rb_vm_backtrace_str_ary 4887 thread.c       	rb_str_concat(msg, rb_ary_join(rb_vm_backtrace_str_ary(th, 0, 0), sep));
rb_vm_backtrace_str_ary  814 vm_backtrace.c     return rb_vm_backtrace_str_ary(GET_THREAD(), 0, 0);
rb_vm_backtrace_str_ary   31 vm_eval.c      VALUE rb_vm_backtrace_str_ary(rb_thread_t *th, int lev, int n);
rb_vm_backtrace_str_ary 1280 vm_eval.c      	VALUE bt2 = rb_vm_backtrace_str_ary(th, 0, 0);