Q123160: FIX: Conditional Breakpoint Doesn’t Stop in Recursive Function

Article: Q123160
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbDebug kbidekbfixlist
Last Modified: 27-JUL-2001

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The information in this article applies to:

- The Integrated Debugger, included with:
   - Microsoft Visual C++, versions 1.5, 1.51 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.0, 2.10 
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SYMPTOMS
========

Using "Break when Expression is True" in a recursive function in the Visual C++
integrated debugger may fail to stop program execution even if the expression
becomes true.

RESOLUTION
==========

Instead of using "Break when Expression is True," use "Break at Location if
Expression is True" to work around the problem.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was not reproducible in Microsoft Visual
C++, 32-bit Edition, version 4.0.

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

To demonstrate the problem, build the sample code below for debug mode and do
the following:

1. Choose Breakpoints... from the Debug menu.

2. In the Breakpoints dialog, select "Break when Expression is True" for the
  Type field.

3. In the Expression field, type "{function1}(i==2)" (without the quotation
  marks) to specify the expression.

4. Add the above breakpoint to the "Breakpoints:" list.

5. Start the debugger. You will notice that the debugger terminates the debug
  session without breaking, even though i was equal to 2 at one point.

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

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

  #include <stdio.h>

  int function1( int i, int j )
  {
    if ( i>0 )
    {
      return function1( i-1, j+1 );
    }
    else
    {
      return j;
    }
  }

  void main(void)
  {
    int i;

    printf( "Before Recursive Call.\n" );
    i = function1( 10, 0 );
    printf( "Back from Recursive Call.\n" );
  }

Additional query words: 1.00 1.50 2.00 2.10

======================================================================
Keywords          : kbDebug kbide kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbIntegratedDebugger
Version           : winnt:
Issue type        : kbbug
Solution Type     : kbfix

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