Q172992: FIX: /Og Causes C1001 While Looping

Article: Q172992
Product(s): Microsoft C Compiler
Version(s): WINNT:5.0
Operating System(s): 
Keyword(s): kberrmsg kbCompiler kbVC500bug kbVS97sp2fix
Last Modified: 17-JUL-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
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SYMPTOMS
========

Compiling code similar to the code in the sample below may cause the following
error to be generated:

  fatal error C1001: INTERNAL COMPILER ERROR (compiler file
  'E:\utc\src\\P2\main.c', line 379)

RESOLUTION
==========

One way to work around the C1001 error is to correct the apparent programming
error in the sample code below. Notice the check of p==0 in the if statement.
The code that follows will cause an access violation if executed. Changing the
check to p!=0 will cause the compiler to not generate the C1001 error and allow
the code to compile. Another workaround that preserves the apparently incorrect
algorithm is to introduce a local integer that holds the result of the
comparison of p to zero. Use this local integer in the if statement instead of
the actual comparison.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual Studio 97 Service
Pack 3.

For additional information about the Visual Studio 97 Service Pack 3, please see
the following article in the Microsoft Knowledge Base:

  Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

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

Sample
------

     // compile options: /Og /c
     int f( int * p )
     {
        int i = 1;
        // int i2 = (p==0); // uncomment these 2 lines and
        // if( i2 )         // 
        if( p == 0 )        // comment this one for workaround
        {
           while( i && *p != 0 )
           {
              i = *p++ == 3;
           }
        }
        return i;
     }

Additional query words: ICE

======================================================================
Keywords          : kberrmsg kbCompiler kbVC500bug kbVS97sp2fix 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : WINNT:5.0
Issue type        : kbbug
Solution Type     : kbfix

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