BUG: Breakpoints Not Hit in ATL MMC Snap-In

• The Microsoft Active Template Library (ATL) 3.0, used with:
  • Microsoft Visual C++, 32-bit Editions, version 6.0
  • The Integrated Debugger

SYMPTOMS

The debugger may not break on your breakpoints when you try to debug an ATL MMC (Microsoft Management Console) Snap-In on a Windows NT 4.0 machine.

CAUSE

The ATL Object Wizard adds code that registers objects differently. The About object uses the DECLARE_REGISTRY() macro for registering itself. Other objects in the same Snap-In use an .rgs file. As a result, the About object is registered using a long file name (in the InprocServer32 key). Other objects are registered with a short file name.

MMC first creates the About object and loads the DLL with the long file name. When other objects are created by MMC, the DLL is reloaded in a different memory location with the short file name. Debugger breakpoints (int 3 instructions) are inserted in the context of the first DLL, so any code executed in the context of the second DLL won't have any int 3 instructions, and therefore breakpoints are not hit.

RESOLUTION

You can use one of the following four workarounds:

• Workaround 1

  Use a directory and project name that does not use long file names.




• Workaround 2

  Change the About object to use the .rgs file as shown below:
  
  
  1. Create a new registry file and edit it as follows (replacing the CLSID and class name):

     
           HKCR
            {
               MyClassAbout.1 = s 'MyClassAbout Class'
               {
                  CLSID = s '{22A88065-391D-11D2-8164-00C04F7948A7}'
                  CurVer = s 'MyClassAbout.1'
               }
               NoRemove CLSID
               {
                  ForceRemove
            {22A88065-391D-11D2-8164-00C04F7948A7} = s 'MyClassAbout Class'
                  {
                     ProgID = s 'MyClassAbout.1'
                     VersionIndependentProgID = s 'MyClassAbout.1'
                     ForceRemove 'Programmable'
                     InprocServer32 = s '%MODULE%'
                     {
                        val ThreadingModel = s 'Both'
                     }
                  }
               }
            } 

  
  
  
  2. Save the new registry file as MyClassAbout.rgs and import this file into your project resource. Change its id to IDR_MYCLASSABOUT.
  
  
  
  3. Replace the DECLARE_REGISTRY line in the About class with the following:

     
        DECLARE_REGISTRY_RESOURCEID(IDR_MYCLASSABOUT) 

  
  
  
  4. Rebuild all.
  
  
  




• Workaround 3

  Unregister the DLL and comment out the object entry for the About object when debugging.




• Workaround 4

  Use _asm int 3 or DebugBreak or ATLASSERT(0) to break into the debugger and set/re-enable your break points.

STATUS

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

Additional query words: snapin

Keywords : kbDebug kbVC600bug kbATL300 kbATL300bug kbfaq kbGrpDSTools
Version : WINDOWS:3.0
Platform : WINDOWS
Issue type : kbbug