to_s

static VALUE
fiber_to_s(VALUE fibval)
{
    const rb_fiber_t *fib;
    const rb_proc_t *proc;
    char status_info[0x10];

    GetFiberPtr(fibval, fib);
    snprintf(status_info, 0x10, " (%s)", fiber_status_name(fib->status));
    if (!rb_obj_is_proc(fib->first_proc)) {
        VALUE str = rb_any_to_s(fibval);
        strlcat(status_info, ">", sizeof(status_info));
        rb_str_set_len(str, RSTRING_LEN(str)-1);
        rb_str_cat_cstr(str, status_info);
        return str;
    }
    GetProcPtr(fib->first_proc, proc);
    return rb_block_to_s(fibval, &proc->block, status_info);
}