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FIX: Visual Studio 2010 may crash when you expand an F# discriminated union in the Locals window


Symptoms

Consider the following scenario:
  • You create a Visual F# Silverlight 4 library in Microsoft Visual Studio 2010 Service Pack 1 (SP1). Additionally, you define a multiple-case discriminated union. For example, you create an F# discriminated union as follows:
    module M
    type T =
    | Leaf of int
    | Tree of T
  • You create a Silverlight 4 application that references the F# library. 
  • You create an instance of the discriminated union. For example, you create a variable x by using the following C# code:
    var x = M.T.NewLeaf(3);
  • You debug the Silverlight 4 application in Visual Studio, and then you set a breakpoint after the variable is constructed.
  • You try to expand the variable x in the Locals window.
In this scenario, Visual Studio 2010 crashes.

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Cause

The issue occurs because discriminated unions in the F# language generate a DebuggerTypeProxy object for each union case label in multi-case discriminated unions. This presents a better view for the debugger in Visual Studio. The type names that are used in the DebuggerTypeProxy objects for these union cases were not handled correctly by the debugger and therefore a crash occurs.

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Resolution

Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

To apply this hotfix, you must have Visual Studio 2010 SP1 installed.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfix.

File Information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
For all supported versions of Visual Studio 2010
File nameFile versionFile sizeDateTimePlatform
Cscompee.dll10.0.40219.3661,031,44029-Nov-201123:53x86

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Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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More Information

For more information about Discriminated Unions (F#), visit the following MSDN website:
Discriminated Unions (F#)

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Keywords: kbqfe, kbhotfixserver, kbfix, kbhotfixdev, kbexpertiseadvanced, kbsurveynew, kb

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Article Info
Article ID : 2535320
Revision : 1
Created on : 1/7/2017
Published on : 1/10/2012
Exists online : False
Views : 83