The first is that a superstructure of substring and concatenation nodes must be traversed to reach a specified character.
第一个开销就是必须遍历子串和连接节点的上层结构（superstructure）才能到达指定的字符。
2
Both wide and non-wide character strings were specified for concatenation.
为串联同时指定了宽字符字符串和非宽字符字符串。
3
Concatenation of files can be a problem also, for example, when files are merged in such a way that an unnecessary character can end up in the middle of data.