Q201830: BUG: Error C2011 When Reusing Nested Structure Tag Names

Article: Q201830
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,4.0,5.0,6.0
Operating System(s): 
Keyword(s): kbConly kbVC200 kbVC400 kbVC500 kbVC600
Last Modified: 03-MAY-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 4.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

When the same tag name is used to declare nested structures inside different
base structure declarations, the follow error is generated:

  error C2011: '<identifier>' : '<type>' type redefinition

NOTE: The C++ compiler does not generate this error.

RESOLUTION
==========

To work around this problem, either don't use tag names for nested structures,
or use unique tag names for all structures.

STATUS
======

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

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

The following code fails to compile with the C compiler. Error C2011 is reported
at the second use of "tag_LEVEL2" and "tag_LEVEL3". This error does not occur
using the C++ compiler.

  /* Defining "A" structure */ 
  struct tag_STRUCTA {

     struct tag_LEVEL2 {
        int   member_a2;

        struct tag_LEVEL3 {
           int member_a3;
        };
     };
  };

  /* Defining "B" structure */ 
  struct tag_STRUCTB {

     struct tag_LEVEL2 {
        int   member_b2;
     };
     struct tag_LEVEL3 {
        int member_b3;
     };
  };

Additional query words:

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Keywords          : kbConly kbVC200 kbVC400 kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:2.0,4.0,5.0,6.0
Issue type        : kbbug
Solution Type     : kbnofix

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