FIX: CXX0033 Error in OMF Type from Forward Class Declaration

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Article ID: 131147 - View products that this article applies to.
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In the Visual C++ debugger, if you debug an application built using precompiled header (PCH) options, the debugger's expression evaluator may generate errors when viewing classes that were declared but not defined in the precompiled header file.

One of the following errors may be generated depending on the Visual C++ version:
CXX0017 Error: symbol "xxxx" cannot be found
CXX0030 Error: expression cannot be evaluated
CXX0033 Error: error in OMF type information
CV1255 Error: no data members
NOTE: The first error message is very generic, and can occur for several different reasons including this one.


When the compiler writes out type information into the program database (.PDB) file, incomplete type information is written for the forward class declaration when the full definition has not yet been compiled.

When the module containing the full class definition is compiled, the complete type information is not replacing the incomplete type information in the .PDB file.


Here are three possible workarounds:

  • Turn off PCH usage. This avoids the problem altogether. -or-

  • Include the full definition of the class in .PCH file. This causes the complete type information to be written to the .PDB file. -or-

  • Compile using C7 Compatible Debug Info switch (/Z7). This will not use a .PDB file to store type information. You may also need to use the /Yd option to include PCH debug information in all object modules.


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.


The following small sample application reproduces the problem. In the Visual C++ integrated debugger, it is not possible to expand "A" in the locals window, watch window, or with a quickwatch.

Sample Code to Demonstrate Problem

/* PCH.H
class FwdNonPCHClass;

class PCHClass
   int i;
   long l;
   class FwdClass * FwdNonPCHClassPtr;

   Win32 Compile options needed: /Yc"pch.h" /Od /Zi /c
   Win16 Compile options needed: /Yc"pch.h" /Od /Zi /Mq /c

#include "pch.h"

   Win32 Compile options needed: /Yu"pch.h" /Od /Zi test.cpp stdpch.obj
   Win16 Compile options needed: /Yu"pch.h" /Od /Zi /Mq test.cpp stdpch.obj

#include "pch.h"

class FwdNonPCHClass
 int i;
 long l;

void main(void)
FwdNonPCHClass A;
PCHClass B;

A.i = 1;
A.l = 17L;

B.i = 54;
B.l = 17L;


Article ID: 131147 - Last Review: July 5, 2005 - Revision: 1.1
  • Microsoft Visual C++ 1.0 Professional Edition
  • Microsoft Visual C++ 1.5 Professional Edition
  • Microsoft Visual C++ 1.51
  • Microsoft Visual C++ 1.52 Professional Edition
  • Microsoft Visual C++ 2.0 Professional Edition
  • Microsoft Visual C++ 2.1
kbbug kbcompiler kbdebug kbfix kbide KB131147
Retired KB Content Disclaimer
This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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