DOCUMENT:Q281424  28-AUG-2001  [visualc]
TITLE   :FIX: Bad Code Is Generated with /Og Enabled
PRODUCT :Microsoft C Compiler
PROD/VER::6.0sp4
OPER/SYS:
KEYWORDS:kbCompiler kbVC600fix kbDSupport

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

 - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0sp4 
 - Microsoft Visual C++, 32-bit Professional Edition, version 6.0sp4 
 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0sp4 
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SYMPTOMS
========

With the global optimizations (/Og) compiler option enabled, the Visual C++ 6.0
Service Pack 4 (SP4) compiler may generate incorrect code for return values to
functions. See the "More Information" section for a detailed reproducible
sample.

CAUSE
=====

This is a regression bug that occurred in Visual Studio Service Pack 4.

RESOLUTION
==========

To work around this bug, do one of the following:

 - Replace the following line in the sample code

   Test (MyClass::Testfunc(), y, z);

   with the following:

   MyClass x = MyClass::Testfunc();
   Test (x , y, z); 

   -or-

 - In the sample code, use #pragma optimize("g", off) before the main function
   to disable the optimizations only in main.

STATUS
======

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

This problem was corrected in Visual Studio 6.0 Service Pack 5.

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

Steps to Reproduce Behavior
---------------------------

   // Test.cpp<BR/>
   // Command line : cl test.cpp /Og

   #include <iostream.h>

   class MyClass
   {
   public:
      unsigned long mID;
      MyClass(unsigned long id);
      MyClass(const MyClass & other);
      MyClass & operator = (const MyClass & other) ;
      unsigned long getID()
      {
   	   return mID;
      }
      static MyClass Testfunc()
      {
   	   return 0;
      };
   };

   MyClass::MyClass (unsigned long id /* = 0 */)
   {
      mID = id;
   }

   MyClass::MyClass(const MyClass & other) : mID(other.mID) 
   {
      cout << "In Copy Constructor" << endl;
   }

   MyClass & MyClass::operator = (const MyClass & other) 
   {
       cout << "In Operator =" << endl;
       mID = other.mID;
       return *this;
   }

   void Test (MyClass x, int y, int z)
   {
      cout << "In Function Test" << endl;
      cout << x.getID() << ' ' << y << ' ' << z << endl;
   }

   int main ()
   {
      int y = 1;
      int z = 2;
      Test (MyClass::Testfunc(), y, z);
      // expected output is 0 1 2
      return 0;
   }

The following is the expected output:

In Function Test
0 1 2

Actual Output:

In Function Test
1245052 0 2

Additional query words: kbbug kbfix

======================================================================
Keywords          : kbCompiler kbVC600fix kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVC32bitSearch kbVC600SP4
Version           : :6.0sp4
Issue type        : kbbug
Solution Type     : kbfix

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

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