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Q115347: PRB: Debugger Cannot Watch Global Constants in C++ Programs

Article: Q115347
Product(s): Microsoft C Compiler
Version(s): 1.0,2.1,4.0,4.01,4.1,5.0
Operating System(s): 
Keyword(s): kbCodeView kbDebug kbide kbVC
Last Modified: 11-FEB-2002

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The information in this article applies to:

- Microsoft Visual Workbench for Windows, version 1.0, used with:
   - Microsoft Visual C++, version 1.0 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.1, 4.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft CodeView for MS-DOS, versions 4.0, 4.01, 4.1 
   - Microsoft CodeView for Windows, versions 4.0, 4.01, 4.1 
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SYMPTOMS
========

On page 17 in chapter 2 of the C++ Tutorial included in Microsoft C/C++, version
7.0 and Visual C++, version 1.0, it states:

  "Constants declared with const have an advantage over those defined by
  #define in that they are accessible to a symbolic debugger, making debugging
  easier."

However, when global constants are used in a C++ program, they cannot be watched
in a local or watch window with CodeView or the Integrated (IDE) Debugger in
Visual C++.

RESOLUTION
==========

The above behavior is by design in the products listed above. In these versions,
with the exception of CodeView 4.25 for Win32S, only local constants are
accessible to CodeView and the Visual C++ IDE debugger.

CAUSE
=====

In Microsoft C++, storage of global constants is optimized for the purpose of
saving space, therefore no debug information is generated.

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

When debugging the following C++ sample program with CodeView, attempting to
watch the global const a yields the following error:

  A = CXX0030: Error: expression cannot be evaluated

Attempting to watch A using the Visual C++ for Windows version 1.0 or the Visual
C++ 32-bit Edition version 1.0 or 2.1 IDE Debugger yields a dialog box with the
following text:

  Cannot watch 'A'.

Attempting to watch A using the Visual C++ 32-bit Edition version 4.0 IDE
Debugger produces the following in the Watch window:

  A = CXX0017: Error: symbol "A" not found

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

     /* Compile options needed: /Zi /Od
     */ 

     const int A=100;
     void main()
     {
        int dummy=0;
        dummy++;
     }

Additional query words: utilities

======================================================================
Keywords          : kbCodeView kbDebug kbide kbVC 
Technology        : kbVSsearch kbAudDeveloper kbVWB
Version           : :1.0,2.1,4.0,4.01,4.1,5.0
Issue type        : kbprb

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