Q117383: BUG: C2483 Instantiating Objects with the Thread Attribute

Article: Q117383
Product(s): Microsoft C Compiler
Version(s): 1.0,2.0,4.0,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVC kbVC100bug kbVC200bug kbVC400bug kbVC410bug kbVC420bug kbVC50
Last Modified: 11-FEB-2002

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 4.0, 4.1, 4.2, 5.0, 6.0 
   - Microsoft Visual C++.NET (2002) 
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SYMPTOMS
========

Instantiating a C++ object with the thread attribute generates the following
error message if the class contains private or protected members:

  error C2483: object with constructor cannot be declared 'thread'

To paraphrase page 397 of the "C++ Language Reference," class objects may be
instantiated with the thread attribute if the objects do not need to be
constructed or destructed. However, this error occurs even though the class does
not have a constructor or a destructor.

CAUSE
=====

Currently, thread local storage has only been implemented for aggregate types.
An aggregate type is defined as an array or object of a class with no
constructors, no private or protected members, no base classes, and no virtual
functions. In this case, private or protected members make the class an
aggregate; therefore, the error message is generated.

RESOLUTION
==========

To avoid this error, make all private or protected members of the class public
members.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

The sample code below demonstrates how to produce and avoid the error message.
Uncomment the "public" keyword before the data member to avoid the error.

Sample Code
-----------

  /* Compile options needed: /c /MT
  */ 

  class B
  {
  // Uncomment the following line to eliminate compiler error
  // public:
        int i;
  };

  __declspec(thread) B b; // error C2483

Additional query words: kbVC400bug 8.00 9.00

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Keywords          : kbCompiler kbCPPonly kbVC kbVC100bug kbVC200bug kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600bug 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :1.0,2.0,4.0,4.1,4.2,5.0,6.0
Issue type        : kbbug

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