Attaching on Startup

Here’s a neat trick I stumbled onto that can make life a lot easier – in our development workstations, certainly, and even in a pinch on staging and testing machines:

How many times have you wished you could attach to a process immediately when it launchs? If we’re running a simple EXE, we can launch it from the debugger directly, but if we’re trying to debug a Windows Service, a scheduled task or a sub-process that is launched automatically, it isn’t that simple. We can try to press CTRL-ALT-P as quickly as possible, but that will almost always miss the very beginning. We can add a call to System.Diagnostics.Debugger.Launch() to our Application_Startup() function (or equivalent), but that’s polluting production code with debugging statements, and it isn’t really something we can send over to a staging or QA machine.

I was all set to write a tool to monitor new processes being launched and latch onto them when I discovered that there’s no need, and Windows provides me with this facility automatically!

All we need to do is create a new registry key under HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File ExecutionOptions and name it after the EXE we want to attach to.

Under this key, we create two values: A DWORD named PauseOnStartup with a value of 1, and a string named Debugger, with a value of vsjitdebugger.exe. Here’s a sample .REG file

Code Snippet
  1. Windows Registry Editor Version 5.00
  2. [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\MyApplication.exe]
  3. “PauseOnStartup”=dword:00000001
  4. “Debugger”=”vsjitdebugger.exe”

 

Now, when MyApplication.exe launches, it will automatically launch the familiar “Choose the debugger to use” dialog, and we can point it to our solution of choice.

One comment

  1. Michael Sutton says:
    Cool. I was recently in desperate need for something like this. Thanks

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