用了好多年了，才发现这个问题，写个小程序测试了，终于搞明白了：CStringstr; str=_T("1234567890");TCHAR*p=str.GetBuffer(100); //TCHAR*p=str.GetBufferSetLength(100);_tcscpy(p,_T("12345678111111190"));str.ReleaseBuffer(); //测试str+="aaa"; m_