Q131000: FIX: Application Error If /Og & Virtual Operator Call in Loop

Article: Q131000
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbCodeGen kbCompiler kbCPPonly kbVCkbbuglist kbfixlist
Last Modified: 25-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 2.0, 2.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

An application error is generated when running a program that meets all these
conditions:

- It was compiled with global optimization (/Og).

- It defines a virtual operator for a class.

- It constructs an object of that class inside a loop.

- The operator is called inside the loop.

CAUSE
=====

The computation of the address of the virtual operator is being lifted out of
the loop.

RESOLUTION
==========

Use any one of the following four workarounds:

- Move the object outside the loop.

-or-

- Use the functional form of the operator.

-or-

- If the operator does not need to be virtual, do not declare it virtual.

-or-

- Do not do global optimizations.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was fixed in Microsoft Visual C++,
32-bit Edition, version 4.0.

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

Sample Code to Reproduce Problem
--------------------------------

  /* Compile options needed: /Og
  */ 
  class Test
  {
  public:
      virtual int operator <= ( const Test& T ) const {return 1;}
  };

  void main( void )
  {
      long i;
      for (i=1; i<=3; i++)
      {
          Test T; //Work-around 1: Move this line above the for loop.
          T <= T; //Work-around 2: Comment out this line, uncomment the next.
          //T.operator<=(T); // Function form of the operator.
      }
  }

Additional query words: 2.00 2.10 9.0 9.1 9.00 9.10

======================================================================
Keywords          : kbCodeGen kbCompiler kbCPPonly kbVC kbbuglist kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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