是C＃/。.NET有符号整数溢出行为定义吗？ [英] Is C#/.NET signed integer overflow behavior defined?

问题描述

在unchecked上下文中，是增加一个整数与保证导致-2147483648值2147483647？

In an unchecked context, is adding one to an integer with value 2147483647 guaranteed to result in -2147483648?

例如，用下面的代码

    const int first = int.MaxValue;
    int second = first;

    if ( second >= first )
    {
        Console.WriteLine( "First check" );
    }

    second++;

    if ( second >= first )
    {
        Console.WriteLine( "Second check" );
    }

在C ++中，这将是非常有效的两个首先检查和第二查询要打印，因为优化可以重用用于第二第一检查结果

In C++, it would be perfectly valid for both "First check" and "Second check" to be printed, as the optimizer can reuse the result of the first check for the second.

是C＃的同一真？

推荐答案

从规格：

4.1.5整数类型

checked和unchecked运算符和语句用来控制溢出检查整型算术运算和转换（§7.6.12）。在checked上下文中，溢出产生编译时错误或导致出现System.OverflowException抛出。 在unchecked上下文中，溢出被忽略，并且不符合目标类型的任何高序位都被放弃。

The checked and unchecked operators and statements are used to control overflow checking for integral-type arithmetic operations and conversions (§7.6.12). In a checked context, an overflow produces a compile-time error or causes a System.OverflowException to be thrown. In an unchecked context, overflows are ignored and any high-order bits that do not fit in the destination type are discarded.

这是我能找到的行为的唯一描述，但似乎不够。所以，是的，加一 Int32.MaxValue 将导致价值 1 使用二进制补码表示。

That is the only description of the behavior that I could find, but it seems sufficient. So yes, adding one to Int32.MaxValue will result in the value -1 using two's complement representation.

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