栈顶的地址就代表最后一次被调用的函数（也就是当前的活动函数）。

The address at the top of the stack represents the function that was last called (that is, the active function).

youdao

在碰到退出函数时，当前的活动函数就会返回，并释放栈顶元素。

When an exit address is encountered, the current active function has returned and the top element on the stack is discarded.

youdao

任务是由栈中的活动组成的，而不是清单文件中声明的某个类或元素。

A task is a stack of activities, not a class or an element in the manifest file.

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