字符类型边界处增量运算符的行为

Behavior of increment operator at bounds for character type(字符类型边界处增量运算符的行为)

问题描述

我想知道 C++ 在这种情况下的表现如何:

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.然而，增量运算符是否将值包装到其下限或发生溢出?

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

发生溢出并导致未定义行为.

第 5.5 节:

如果在计算表达式期间，结果不是数学定义或不在可表示值的范围内对于它的类型，行为是未定义的[...]

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 [...]

该标准继续指出，在大多数实现中，整数溢出会被忽略.但这并不代表保证.

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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