Microsoft KB Archive/306083

= FIX: Visual C++ compiler optimizer may remove loops =

Article ID: 306083

Article Last Modified on 9/26/2005

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APPLIES TO


 * Microsoft Visual Studio .NET 2002 Professional Edition
 * Microsoft Visual Studio .NET 2002 Enterprise Architect
 * Microsoft Visual Studio .NET 2002 Enterprise Developer
 * Microsoft Visual Studio .NET 2002 Academic Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition

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This article was previously published under Q306083



SYMPTOMS
Under certain, rare conditions, the C++ compiler may optimize loops out of a program. When you examine the compiled assembler, you may note that there are functions that do not contain looping instructions, although the source code contains loop constructs.



CAUSE
This problem occurs because of a bug in the global optimizer.



Service pack information
To resolve this problem, obtain the latest service pack for Microsoft Visual Studio .NET. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

837234 List of bugs that are fixed in Visual Studio .NET 2002 Service Pack 1

Hotfix information
The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

  Date          Version       Size        File name -  11-Apr-2002   13.0.9485.0   1,753,088   C2.dll 11-Apr-2002  13.0.9485.0   2,105,344   C1xx.dll



WORKAROUND
To work around the problem, use a larger data type as the iterator value.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section. This problem was first corrected in Visual Studio .NET 2002 Service Pack 1.



MORE INFORMATION
The following program is an example of the behavior. After you build this sample program by using the default compiler settings for release mode, it prints out Loop only one time.
 * 1) include 
 * 2) include 
 * 3) include 

int __cdecl _tmain (int argc, _TCHAR* argv[]) {   unsigned char stream, tmp;

for (stream = 0; stream < 4; stream++) {       tmp = stream; fprintf (stderr, &quot;Loop\r\n&quot;, (unsigned char)((tmp+4)<<5)); }   return 0; }

Keywords: kbbug kbfix kbqfe kbvs2002sp1sweep kbvs2002sp1fix kbhotfixserver KB306083

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