// Dump stack trace of threads specified in the given threads array.
// Returns StackTraceElement[][] each element is the stack trace of a thread in
// the corresponding entry in the given threads array

Handle ThreadService::dump_stack_traces(GrowableArray<instanceHandle>* threads,
                                        int num_threads,
                                        TRAPS) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert(num_threads > 0, "just checking");

  {- -------------------------------------------
  (1) VM_ThreadDump::doit() でスタックトレースを取得する.
      ---------------------------------------- -}

      ThreadDumpResult dump_result;
      VM_ThreadDump op(&dump_result,
                       threads,
                       num_threads,
                       -1,    /* entire stack */
                       false, /* with locked monitors */
                       false  /* with locked synchronizers */);
      VMThread::execute(&op);

  {- -------------------------------------------
  (1) 返値は java.lang.StackTraceElement[][] としてリターンする必要があるので, 
      oopFactory::new_objArray() で新しい java.lang.StackTraceElement[][] オブジェクトを確保し
      VM_ThreadDump::doit() の結果をそちらに詰め直す.
      ---------------------------------------- -}

      // Allocate the resulting StackTraceElement[][] object

      ResourceMark rm(THREAD);
      klassOop k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_StackTraceElement_array(), true, CHECK_NH);
      objArrayKlassHandle ik (THREAD, k);
      objArrayOop r = oopFactory::new_objArray(ik(), num_threads, CHECK_NH);
      objArrayHandle result_obj(THREAD, r);

      int num_snapshots = dump_result.num_snapshots();
      assert(num_snapshots == num_threads, "Must have num_threads thread snapshots");
      int i = 0;
      for (ThreadSnapshot* ts = dump_result.snapshots(); ts != NULL; i++, ts = ts->next()) {
        ThreadStackTrace* stacktrace = ts->get_stack_trace();
        if (stacktrace == NULL) {
          // No stack trace
          result_obj->obj_at_put(i, NULL);
        } else {
          // Construct an array of java/lang/StackTraceElement object
          Handle backtrace_h = stacktrace->allocate_fill_stack_trace_element_array(CHECK_NH);
          result_obj->obj_at_put(i, backtrace_h());
        }
      }

  {- -------------------------------------------
  (1) 結果をリターン
      ---------------------------------------- -}

      return result_obj;
    }