为i = 0，+我定义？ [英] Is i = 0, ++i defined?

问题描述

我最近了解了，运营商，它引入了的序列点的事实的

I recently learned about the , operator and the fact that it introduces a sequence point.

我还了解到，以下code导致不确定的行为：

I also learned that the following code led to undefined behavior:

i = ++i;

由于 I 在两个序列点之间两次修改

Because i was modified twice between two sequence points.

但是，我们下面的codeS？

But what about the following codes ?

i = 0, ++i;
i = (0, ++i);

虽然我知道规则，我不能得到一个结论。因此，它是定义的行为或不？

While I know the rules, I can't get to a conclusion. So is it defined behavior or not ?

编辑：正如@paxdiablo提到，的定义与否的，这的确是一个坏习惯应该避免的。这个问题是问仅用于教育目的和更好地理解规则。

edit: Just as @paxdiablo mentions, defined or not, this is really a bad practice which should be avoided. This question is asked solely for educational purposes and better understanding of the "rules".

推荐答案

是的。 = 具有较高的precedence比，，所以这个前pression等同于（I = 0），++我。 ，是一个序列点，所以它保证了 ++我转让后发生。

Yes. = has higher precedence than ,, so this expression is equivalent to (i = 0), ++i. , is a sequence point, so it's guaranteed that the ++i occurs after the assignment.

我不知道是否 I =（0，+ I）虽然是定义。我的猜测是没有;还有的增量和分配之间没有顺序点。

I'm not sure whether i = (0, ++i) is defined though. My guess would be no; there's no sequence point between the increment and the assignment.

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