问Excel VBA脚本在调用用C编写的DDL函数时崩溃，该函数返回字符串BSTR

EN

#define MQTTPUB_VERSION "V3.1.1Test"
DLL_EXPORT BSTR __stdcall WINAPI getVersion(void)
{
  return MQTTPUB_VERSION ;
}

Public Declare Function mqttPubMsg Lib "mqttPubMsg.dll" _
 (ByVal MQTT_ADDRESS As String, ByVal MQTT_CLIENTID As String, ByVal MQTT_TOPIC As String, ByVal MQTT_PAYLOAD As String) As Long
Public Declare Function getVersion Lib "mqttPubMsg.dll" () As String
Sub Test_DDL_mqttPubMsg()
'
' to test mqttPubMsg.DLL used in Visual Basic (VBA)
'
Dim DLLVersion As String * 35
Dim WorkDir As String
DLLVersion = Space(35)
WorkDir = ThisWorkbook.Path
ChDir WorkDir

If Dir(WorkDir & "\mqttPubMsg.dll", vbDirectory) = vbNullString Then
   MsgBox "DLL not found"
Else
  On Error GoTo DLLError
  DLLVersion = getVersion() 'Excel crashes on executing this statement
End If
MsgBox ("Version DDL: " & DLLVersion)
Exit Sub
DLLError:
  MsgBox ("DDL error")
End Sub