Writing a script debugger without using the MDM

Today’s blog is about writing your own script debugger.

Visual Studio has provided ‘Script’ debugging for a long time. In this context, ‘Script’ refers to script run by jscript.dll or vbscript.dll such as the script code in Internet Explorer, classic ASP scripting, or the cscript/wscript programs. Long long ago, someone provided a sample for creating your own script debugging utilizing the active script debugging interfaces (ex: IRemoteDebugApplication).

However, this sample relied on a Microsoft executable called mdm.exe (IMachineDebugManager/CLSID_MachineDebugManager). After Visual Studio 2003, Visual Studio stopped shipping mdm.exe. So today, I wanted to provide a brief summary of how one could port an mdm.exe-based script debugger to the newer interfaces. Mdm.exe provided essentially two related features -- it allowed a debugger determine what script applications where currently running, and there was an eventing interface that let a debugger be informed when a new script application started. These features worked because the debugger component inside of the target process (pdm.dll) would connect to mdm.exe whenever a new script application was created.

Today, these features have been moved to pdm.dll. So now, pdm.dll is loaded in both the debugger and in the target process. In the target process pdm.dll still continues to do the same work as it has always done. However, now one can also load pdm.dll into the debugger process to obtain the old MDM features.

PDM now has a new CLSID for the work that it does in the debugger process – CLSID_MsProgramProvider. It exposes an AD7 interface for obtaining this information: IDebugProgramProvider2.

There is sample code attached to this blog which demonstrates how to launch or attach to a program using these new interfaces.


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