This routine initially checks to see if NULL manager entry point vector, mgr_epv, was passed.

这个例程首先检查传递的管理器入口点向量mgr_epv是否是NULL。

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For those methods to accept no argument would require a null where point was specified.

对于不接受参数的方法，在指定point的地方需要一个null。

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Also, many times member variables of a class that point to other classes simply need to be set to null at the appropriate time.

此外，您常常需要在适当的时候将指向其他类的类成员变量设置为null。

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