FIX: Code compiled with the /Og option in Visual C++ 6.0 can cause incorrect calculation for doubles (217033)



The information in this article applies to:

  • Microsoft Visual C++, 32-bit Enterprise Edition 6.0
  • Microsoft Visual C++, 32-bit Professional Edition 6.0
  • Microsoft Visual C++, 32-bit Learning Edition 6.0

This article was previously published under Q217033

SYMPTOMS

Code compiled with the /Og option can cause incorrect calculation for doubles. In some cases, it loads only half of a double's bytes into memory causing incorrect results in later calculations.

RESOLUTION

Disable global optimizations.

Global optimizations can be disabled for the entire project or for a particular source file by removing /Og from either the project's release build compiler settings or an individual file's release build compiler settings.

Note /O1 (minimize size) and /O2 (maximize speed) are composite switches that include /Og. If you are using /O1 or /O2 disable global optimizations by adding /Og- to the appropriate compiler settings.

Global optimization can also be disabled on a function by function basis through the use of #pragma optimize as follows.
#ifndef _DEBUG  // current build is not a debug build<BR/>
#pragma optimize("g", off) // disable global optimization<BR/>
#endif // _DEBUG<BR/><BR/>
void SomeFunction()<BR/>

*** Body of SomeFunction Here ***
return;

#ifndef _DEBUG // current build is not a debug build<BR/>
#pragma optimize("g", on) // re-enable global optimization<BR/>
#endif // _DEBUG<BR/>
				

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, click the following article numbers to view the articles in the Microsoft Knowledge Base:

194022 Visual Studio 6.0 service packs, what, where, why

194295 How to tell that a Visual Studio service pack is installed


Modification Type:MajorLast Reviewed:9/7/2005
Keywords:kbQFE kbBug kbCompiler kbfix kbVS600sp3fix KB217033 kbAudDeveloper