在处理函数中，我们获得了一个指向保存了位置信息的YYLTYPE结构的指针，这样可以生成一条很好的错误消息。

In the processing function, you get a pointer to the YYLTYPE structure holding the location, and you can generate a nice error message.

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每次您调用一个可以返回错误值的函数时，就必须小心地检查请求所生成的结果正是您所希望的(如果不是，就需要对错误进行处理)。

Every time you call a function that can return an error, you need to be careful to check that your request produced the result you expected (or handle the error if it didn't).

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如果底层的函数处于关键部分，并且生成并处理信号，那么这可能会导致函数不可重入。

If the underlying function is in the middle of a critical section and a signal is generated and handled, this can cause the function to be non-reentrant.

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