BUG: You receive a "fatal error C1001" error message when you try to unbox an enumeration (327972)

The information in this article applies to:

Microsoft Visual C++ .NET (2002)

This article was previously published under Q327972

SYMPTOMS

When you try to unbox an enumeration instance, you receive the following compiler error message:

You receive a "fatal error C1001" error when you try to unbox an enumeration: INTERNAL COMPILER ERROR
(compiler file 'msc1.cpp', line 2844)
Please choose the Technical Support command on the Visual C++ Help menu,
or open the Technical Support help file for more information.

WORKAROUND

To work around this problem, cast to the underlying type of the _value enum, and then cast to the enum type. For example, to unbox an enumeration instance, instead of using the following code:

SomeEnum enum2 = *dynamic_cast<__box SomeEnum*>(obj);

use the following code:

SomeEnum enum2 = (SomeEnum)*__try_cast<Int32*>(obj);

because the underlying type of _value enum is Int32.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce the Problem

In Visual C++ .NET, create a new Managed C++ Application project.

In the default .cpp file that is generated for your application, replace the default code with the following code:

#include "stdafx.h"
#using <mscorlib.dll>
using namespace System;

__value enum SomeEnum
{
    SomeValue = 0
};


int main(void)
{
	SomeEnum enum1 = SomeValue;
	Object* obj = __box(enum1);
	SomeEnum enum2 = *dynamic_cast<__box SomeEnum*>(obj); 
	return 0;
}

Build the application.

You receive the error message that is described in the "Symptoms" section of this article.

REFERENCES

For additional information about Managed Extensions for C++, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn.microsoft.com/library/en-us/vcmxspec/html/vcManagedExtensionsSpec_5.asp

Modification Type:	Major	Last Reviewed:	1/6/2006
Keywords:	kbProd2Web kbCompiler kberrmsg kbbug kbManaged KB327972 kbAudDeveloper kbAudITPRO