增量运算符在字符类型边界上的行为 [英] Behavior of increment operator at bounds for character type

问题描述

我想知道C ++在这种情况下的行为：

I wonder how C++ behaves in this case:

char variable = 127;
variable++;

在这种情况下，变量现在等于-128。但是，增量运算符是将值包装到其下限还是发生溢出？

In this case, variable now equals to -128. However did the increment operator wrapped the value to its lower bound or did an overflow occurred?

推荐答案

发生溢出并导致< 。

An overflow occured and results in undefined behavior.

第5.5节：

表达式的求值，结果不是在数学上定义的
或不在其类型的可表示值
的范围内，行为未定义[...]

Ifduring the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined [...]

标准继续指出，在大多数实现中，整数溢出都被忽略。但这并不表示保证。

The standard goes on to note that integer overflows are, in most implementations, ignored. But this doesn't represent a guarantee.

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