How do I debug an exe running through Windows Scheduler? [duplicate] - debugging

This question already has answers here:
How can I use DebugBreak() in C#?
(5 answers)
Closed 2 years ago.
I'm using Windows Scheduler to run an exe I have written.
How can I jump into a debug session when the scheduler starts my exe?
Update 1.
I had thought of doing a Thread.Sleep and then Attach to Process. When I tried it, it says Debugger is already attached to process...

You could just call DebugBreak() from within your program.
According to the MSDN page, DebugBreak does the following:
Causes a breakpoint exception to occur
in the current process. This allows
the calling thread to signal the
debugger to handle the exception.
To cause a breakpoint exception in
another process, use the
DebugBreakProcess function.
You can then attach your debugger at this point, and continue running the program.
The only problem with this solution is that you need to make the DebugBreak() in the code conditional, so that it won't break every time the program is run. Maybe you achieve this through an environment variable, registry setting, or a parameter which the scheduler passes in to the program to ensure that it breaks when it starts up.
Example code
Here's some untested example code reading an environment variable:
int main()
{
char *debugBreakChar = getenv("DEBUG_BREAK");
int debugBreak = atoi(debugBreakChar);
if (debugBreak)
{
DebugBreak();
}
// Rest of the program follows here
}
Now all you need to do is set the environment variable as a system variable, and ensure that it's accessible from the same shell context as the scheduler (rebooting will achieve this):
set DEBUG_BREAK=1
Now the program will break on startup, allowing you to attach a debugger. Changing the environment variable to 0, or un-setting it, will allow the program to run normally.
Environment variables are a bit fiddly in this regard, as they are context-based and you need to know that the scheduler runs from the same environmental context. Registry values are better than this, and you can read a registry value using RegQueryValueEx in your code instead (you'll need to include windows.h to use this function).

Attach to Process will work (from within Visual Studio), although you may need to add a sleep statement at the beginning of your code if it is a fast process so that you can attach before it starts your main logic.

You can set a key under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options that will attach debugger to the process when the process is launched. You can read how to do this in this KB Article.
There are couple of gotchas with this approach:
IFEO debugging does not work with pure managed debugging. You need to use Interop Debugging
You might need to remote your debugger to another session, depending on what user the Scheduler launches your app as.
To debug using VS, you need to actually specifyg VSJitDebugger.exe in the IFEO options for your executable. You will also have to specify the debugging engine to use manually. More details here.

"Attach to Process" in Visual Studio's Debug menu.

Related

Have VC++ executable automatically load debugger [duplicate]

This question already has answers here:
debugging a process spawned with CreateProcess in Visual Studio
(3 answers)
Closed 7 years ago.
I have a program running which loads up a separate program to do some work for it. That separate program is run from the first, using Process.Start() and I need it to load into the Visual Studio debugger to single step through it.
Unfortunately, though I can run the first program in a debugger session, it still starts the second as a "proper" process. I need to have this second program open up in a debugger session. Normally I would just attach a debugger to the process once it's started but, in this case, I need it to breakpoint very early on (in the CInitDialog() function) and, as fast as I am, I can't outrun the code in this case.
A solution I found right here on Stack Overflow said to use Debugger.Launch() but that appears to be specific to C#.
I also thought of trying to cause a crash in the code (such as with a null pointer reference) to load up the debugger but I suspect this would mean single stepping would then be unavailable to me.
How can I do this?
Visual C++ has a similar feature to the C# Debugger.Launch(), it's called DebugBreak(). This actually breaks the application and it will present you with a dialog box asking how you want to handle it:
If you select Debug the program at that point, it will then ask you whether you want to do it in a new Visual Studio session or an existing one. I tend to have the solution already open so I can effectively attach to that one - opening a new instance gives you just the file rather than the entire solution.
So you can simply insert that call in your code where you want to break, and allow the first program to run it as per normal. The second program will start up and break where you've placed the statement and you can then single-step and do all the other wondrous things a debugger allows.

How to break a process on start

With visual studio you can attach to a running process, hit 'pause' (or called break), and even without symbol files or source, you've paused the process and can see a disassembled view.
I would like to achieve this but at the very start of the process. Attaching and pausing as quickly as possible is not the solution I'm looking for :)
For example, if the application was a console based c++ app, gdb can set a break point on main() [or any named function it can find for that matter]. Can something similar be done with visual studio?
But this question is for the more general case - I'd like to be able to start a process and have it pause immediately upon entry (immediately after the kernel launches the process).
http://blogs.msdn.com/b/greggm/archive/2008/09/12/attaching-a-debugger-at-startup.aspx
There are some level of support. But if I were you, I would use WinDbg directly.

What's the advantage for 'attach to process' compared with 'Start Debugging'?

I am new to programming.
I know only Start debug before. Maybe start debug suit for some small application develop better.
I found Visual studio IDE provide another method of attach to process for using.
When & Why must I use the attach debugging?
Such as multi-threading application debugging. Client/Service application debugging. etc. Thank you.
Sometimes you need to debug a process started by another program.
For example you need a reliable solution and in order to protect against access violations, memory leaks and other barely recoverable stuff, you have a master program and several worker programs. The master program starts the worker program and passes parameters to it. How do you debug a worker program which is not intended to be started by anything except the master program?
You use "attach to process for that".
Typically you do it this way: insert a statement that blocks the worker program for some time - for example, call Sleep() for 15 seconds. Then you kindly ask the master program to start the worker program. When the worker program is started it blocks and you now have 15 seconds to attach to it.
This way you can debug almost any issues - problems at early startup stages, wrong parameters, etc, which you wouldn't reliably reproduce with "run with debugging".
Attaching to a process is useful if you don't want to debug right from starting the process. For example, debugging usually slows down execution, so it can be quicker to start the app, get it to a state where a bug appears, and then attach a debugger.
It's also useful if you already have an external means of launching the process that you don't want or can't to import into the IDE.
Start debugging from VS launches an instance of the VS webserver and attaches the debugger to it.
Attach to process allows you to attach to any process and debug it, usually you'd do this to your instance of w3wp.exe running your code in IIS
Attach to process is mostly used when you can't run the application from Visual Studio.
For example, if it's a service or if it is a process that has run for a long time and now you want to start debugging it.
Sometimes you also want to debug a remote process, not on your machine - and you can do that using attach to process.

Automatically attach vs2005 debugger to a child processes

I have a main C++ app built in Visual Studio 2005, called A.exe. It spawns a child process, B.exe. I run process A in the debugger by hitting F5 -- the only way I know to hit breakpoints in process B is to wait for A to kick it off, then run Debug -> Attach to Process, and manually select B.exe. This doesn't work very well if I need to debug initialization code in process B -- I have to start putting in 10 second sleeps at the beginning.
Is there some trick in the vs2005 GUI that I'm missing?
I'm using native code, by the way.
Thanks,
Nathan
You can tell Windows to automatically attach the debugger when a certain process is started (by specifying the process name in a registry setting).
The details are here:
http://msdn.microsoft.com/en-us/library/a329t4ed(v=vs.100).aspx
You'd be hard pushed to make use of the debugbreak command in the child process as the debug process is not yet attached.
However, there is another that may be of use. Seeing as your creating the process, you'll have the handle to it. So give the DebugBreakProcess function a whirl.

How can I debug a process (1.exe) running under another process (2.exe)?

1.exe doesn't give enough time for me to launch the IDE and attach 1.exe to the debugger to break into.
I would suggest taking the same approach as with NT services in this case. They will also start and usually not give you enough time to attach the debugger for the start-up routines.
Details are described here: http://www.debuginfo.com/articles/debugstartup.html
In short you add a registry entry for the second exe:
HKLM\Software\Microsoft\Windows
NT\CurrentVersion\Image File Execution
Options\2.exe Debugger =
"c:\progs\msvs\common7\ide\devenv.exe
/debugexe" (REG_SZ)
Change the c:\progrs\msms\ to match your settings.
Hope that helps.
I assume you have the source to 1.exe (if you're debugging it), then just insert a statement near the beginning that will cause it to hang around long enough to attach a debugger. ( getch() if you're desperate and it's not interactive. )
After the attach, just skip to the next statement and let it go.
You could put in some preprocessor commands for debug builds - just remember to build your release in release mode:
#ifdef DEBUG
Thread.Sleep(10000);
#endif
How is 1.exe launched? If you can launch it using CreateProcess(), you can start the process in a suspended state, attach the debugger, then release the new process.
If you are willing to consider a debugger other than Visual Studio, WinDBG can auto-debug child processes (native code only).
You did not mention what language you are using. But if you using C# or VB.NET you can add Debug.Break() or Stop to trigger the prompt to attach debugger to the process.
Or as mentioned above just use something like Console.Readline() or MessageBox.Show() to pause starting of process untill you can attach debugger to it.

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