调试器离奇三元操作行为对x64平台 [英] Bizarre ternary operator behavior in debugger on x64 platform

问题描述

我用一个很简单的三元表达我的C＃代码：

I'm using a very simple ternary expression in my C# code:

helperClass.SomeData = helperClass.HasData ? GetSomeData() : GetSomeOtherData();

在这两种情况下，表达的每个路径上的函数返回一个非空的对象，但是，如果我看结果在调试器，它为空，直到我引用它的代码，如使用断言：

In both cases, the functions on each path of the expression return a non-null object, but if I look at the result in the debugger, it is null until I reference it in the code such as using an assert:

Debug.Assert(helperClass.SomeData != null);

这才会出现，如果我用一个64，或在调试任何CPU平台设置发生模式。它在86的模式很好。

This only appears to happen if I use an "x64" or "Any CPU" platform setting in Debug mode. It's fine in "x86" mode.

我尽量假设我发现在编译器或调试错误之前非常谨慎，但我不能找到任何。别的解释这种行为

I try to be very cautious before assuming I've found a bug in the compiler or debugger, but I can't find any other explanation for this behavior.

下面是一个完整的类做一个摄制，只需调用SomeClass.SomeAction（）在64位模式下的调试器和单步看看吧：

Here's a full class to do a repro, just call SomeClass.SomeAction() in the debugger in x64 mode and step through to see it:

public class SomeClass {
    public bool HasData;
    public object SomeData;

    private SomeClass() {
        HasData = false;
    }

    public static void SomeAction() {
        var helperClass = new SomeClass();
        // Exhibits weird debugger behavior of having helperClass.SomeData = null after this line:
        helperClass.SomeData = helperClass.HasData ? GetSomeData() : GetSomeOtherData();

        // Note that trying helperClass.SomeData.ToString() returns a debugger error saying SomeData is null

        // But this code is just fine
        //if(helperClass.HasData) {
        //    helperClass.SomeData = GetSomeData();
        //} 
        //else {
        //    helperClass.SomeData = GetSomeOtherData();
        //}

        // In both cases though, after this line things are fine:
        Debug.Assert(helperClass.SomeData != null);
    }

    private static object GetSomeData() {
        return new object();
    }

    private static object GetSomeOtherData() {
        return new object();
    }
}

我缺少的东西，或者这是一个臭虫在64位调试器吗我使用调试模式，因此没有优化应该存在。

Am I missing something or is this a bug in the x64 debugger? I'm using debug mode so no optimizations should be present.

推荐答案

拍摄埃里克利珀特的建议，这可能是一个错误，我已经提交了正式的连接错误此问题： https：//开头连接.microsoft.com / VisualStudio中/反馈/信息/ 684202

Taking Eric Lippert's advice that this is probably a bug, I've filed an official Connect bug for this issue: https://connect.microsoft.com/VisualStudio/feedback/details/684202

谢谢大家对您的意见！

更新：他们回来对我说，他们已经固定在编译器的下一个版本这个角落情况。万岁！ ：）

UPDATE: They got back to me and said they've fixed this corner case in the next version of the compiler. Hooray! :)

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