Enumerable.Sum（）溢出 [英] Enumerable.Sum() overflowing

问题描述

嘿，我使用了 Enumerable.Sum（）的扩展方法从LINQ来计算哈希值codeS，和我有与<$ C $的问题C> OverflowExceptions 时，code变大。我试图把在选中块中的电话，但似乎并没有帮助。

Hey, I'm using the Enumerable.Sum() extension method from LINQ to compute hash codes, and am having a problem with OverflowExceptions when the code gets big. I tried putting the call in an unchecked block, but that didn't seem to help.

MSDN文档的方式说，如果该值变得太大就会抛出，但我在反射检查，这是所有有：

The MSDN documentation for the method says it will throw if the value gets too big, but I checked in reflector and this is all there is:

public static int Sum(this IEnumerable<int> source) {
    if (source == null) {
        throw Error.ArgumentNull("source");
    }
    int num = 0;
    foreach (int num2 in source) {
        num += num2;
    }
    return num;
}

根据这个反编译，我希望它或者溢出与否取决于调用code的范围内。为什么四溢，我怎样才能得到它停下来？

Based on this decompilation, I would expect it to either overflow or not depending on the context of the calling code. Why is it overflowing, and how can I get it to stop?

推荐答案

在code确实执行在C＃检查块。问题是，反射器是不正确的反编译检查块，而不是将它们显示为正常工科大学生数学运算。您可以通过创建一个检查块，编译code，然后反编译它反射验证这一点吧。

The code is indeed executing in a C# checked block. The problem is that reflector doesn't properly decompile checked blocks and instead shows them as normal mathmatical operations. You can verify this yourself by creating a checked block, compiling the code and then decompiling it in reflector.

您也可以通过查看IL，而不是反编译的C＃code验证这一点。取而代之的是加IL运code，你会看到，除了发生add.ovf。这是加的抛出对溢出的版本

You can also verify this by looking at the IL instead of the decompiled C# code. Instead of the add IL opcode you'll see that the addition occurs with add.ovf. This is the version of add that throws on overflows

L_001a: callvirt instance !0 [mscorlib]System.Collections.Generic.IEnumerator`1<int32>::get_Current()
L_001f: stloc.1 
L_0020: ldloc.0 
L_0021: ldloc.1 
L_0022: add.ovf <-- This is an overflow aware addition
L_0023: stloc.0 
L_0024: ldloc.2 

有没有办法让不扔溢出这种特殊的方法。你最好的选择有以下几种

There is no way to get this particular method to not throw on overflow. Your best options are the following

1. 切换到一个更大的类型，如长
2. 在写你自己的版本总和不使用检查除了

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