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Debug Multiple Processes

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Note

This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Here’s how to start debugging processes, switch between processes, break and continue execution, step through source, stop debugging, and terminate or detach from processes.

Contents

Configure the execution behavior of multiple processes

Find the source and symbol (.pdb) files

Start multiple processes in a VS solution, attach to a process, automatically start a process in the debugger

Switch processes, break and continue execution, step through source

Stop debugging, terminate or detach from processes

Configure the execution behavior of multiple processes

By default, when multiple processes are running in the debugger, the breaking, stepping, and stopping debugger commands usually affect all the processes. For example, when one process is suspended at a breakpoint, the execution of all other processes is also suspended. You can change this default behavior to gain more control over the targets of execution commands.

  1. On the Debug menu, choose Options and Settings.

  2. On the Debugging, General page, clear the Break all processes when one process breaks check box.

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Find the source and symbol (.pdb) files

To navigate the source code of a process, the debugger needs access to the source files and symbol files of the process. See Specify Symbol (.pdb) and Source Files.

If you can’t access the files for a process, you can navigate by using the Disassemby window. See How to: Use the Disassembly Window

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Start multiple processes in a VS solution, attach to a process, automatically start a process in the debugger

Note

The debugger does not automatically attach to a child process that is started by a debugged process, even if the child project is in the same solution. To debug a child process:

  • Attach to the child process after it has been started.

    -or-

    • Configure Windows to automatically start the child process in a new instance of the debugger.

Start debugging multiple processes in a Visual Studio solution

When you have more than one project in a Visual Studio solution that can run independently (projects that run in separate processes), you can select which projects the debugger starts.

Changing the startup type for a project

Change the startup project

To change the startup project for a solution, select the project in Solution Explorer and then choose Set as Startup Project from the context menu.

Start a specific project in a solution

To start a project for a solution without changing the default startup project, select the project in Solution Explorer and then choose Debug from the context menu. You can then choose Start new instance or Step Into new instance.

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Start multiple projects in a solution

  1. Select the solution in Solution Explorer and then choose Properties on the context menu.

  2. Select Common Properties, Startup Project on the Properties dialog box.

  3. For each project that you want to change, choose either Start, Start without debugging, or None.

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Attach to a process

The debugger can also to attach to programs that are running in processes outside of Visual Studio, including programs that are running on a remote device. After you attach to a program, you can use debugger execution commands, inspect the program state, and so on. Your ability to inspect the program might be limited, depending on whether the program was built with debug information and whether you have access to the program's source code, and whether the common language runtime JIT compiler is tracking debug information.

See Attach to Running Processes for more information.

Attach to a process that is running on your local machine

Choose Debug, Attach to Process. On the Attach to Process dialog box, select the process from the Available Processes list, and then choose Attach.

Attach to Process dialog box

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Automatically start a process in the debugger

Sometimes, you might need to debug the startup code for a program that is launched by another process. Examples include services and custom setup actions. In these scenarios, you can have the debugger launch and automatically attach when your application starts.

  1. Start the Registry Editor (regedit.exe).

  2. Navigate to the HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options folder.

  3. Select the folder of the app that you want to start in the debugger.

    If the name of the app is not listed as a child folder, select Image File Execution Options and then choose New, Key on the context menu. Select the new key, choose Rename on the shortcut menu, and then enter the name of the app.

  4. On the context menu of the app folder, choose New, String Value.

  5. Change the name of the new value from New Value to debugger.

  6. On the context menu of the debugger entry, choose Modify.

  7. On the Edit String dialog box, type vsjitdebugger.exe in the Value data box.

    Edit String dialog box

    Automatic debugger start entry in regedit.exe

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Switch processes, break and continue execution, step through source

Switch between processes

You can attach to multiple processes when you are debugging, but only one process is active in the debugger at any given time. You can set the active or current process in the Debug Location toolbar or in the Processes window. To switch between processes, both processes must be in break mode.

To set the current process

  • On the Debug Location toolbar, choose Process to view the Process list box. Select the process that you want to designate as current process.

    Switch between processes

    If the Debug Location toolbar is not visible, choose Tools, Customize. On the Toolbars tab, choose Debug Location.

  • Open the Processes window (shortcut Ctrl+Alt+Z), find the process that you want to set as the current process, and double-click it.

    Processes window

    The current process is marked by a yellow arrow.

    Switching to a project sets it the current process for debugging purposes. Any debugger window that you view will show the state for the current process, and all stepping commands affect only the current process.

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Break, step, and continue commands

Note

By default, the break, continue and step debugger commands affect all processes that are being debugged. To change this behavior, see Configure the execution behavior of multiple processes

Command Break all processes when one process breaks

Checked (Default)		 Break all processes when one process breaks

Cleared
Debug menu:

- Break All		 All processes break. All processes break.
Debug menu:

- Continue		 All processes resume. All suspended processes resume.
Debug menu:

- Step Into
- Step Over
- Step Out		 All processes run while current process steps.

Then all processes break.		 Current process steps.

Suspended processes resume.

Running processes continue.
Debug menu:

- Step Into Current Process
- Step Over Current Process
- Step Out Current Process		 N/A Current process steps.

Other processes maintain their existing state (suspended or running).
Source window

- Breakpoint		 All processes break. Only source window process breaks.
Source window context menu:

- Run to cursor

The source window must be in the current process.		 All processes run while source window process runs to cursor and then breaks.

Then all other processes break.		 Source window process runs to cursor.

Other processes maintain their existing state (suspended or running).
Processes window context menu:

- Break Process		 N/A Selected process breaks.

Other processes maintain their existing state (suspended or running).
Processes window context menu:

- Continue Process		 N/A Selected process resumes.

Other processes maintain their existing state (suspended or running).

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Stop debugging, terminate or detach from processes

  • Stop, terminate, and detach commands

    By default, when you choose Debug, Stop Debugging when multiple processes are open in the debugger, the debugger terminates or detaches from all processes depending on how the process was opened in the debugger:

  • If the current process was launched in the debugger, that process is terminated.

  • If you attached the debugger to the current process, the debugger detaches from the process and leaves the process running.

    For example, if you start debugging a process from a Visual Studio solution, attach to another process that is already running, and then choose Stop Debugging, the debugging session ends, the process that was started in Visual Studio is terminated, while the process that you attached is left running. You can use the following procedures to control the way that you stop debugging.

Note

The Break all processes when one process breaks option does not affect stopping debugging or terminating and detaching from processes.

To change how Stop Debugging affects an individual process

  • Open the Processes window (shortcut Ctrl+Alt+Z). Select a process and then select or clear the Detach when debugging stopped check box.

Stop, terminate, and detach commands

Command Description
Debug menu:

- Stop Debugging		 Unless the behavior is changed by Processes window Detach when debugging stops option:

1. Processes started by debugger are terminated.
2. Attached processes are detached from the debugger.
Debug menu:

- Terminate All		 All processes are terminated.
Debug menu:

- Detach All		 The debugger detaches from all processes.
Processes window context menu:

- Detach Process		 The debugger detaches from the selected process.

Other processes maintain their existing state (suspended or running).
Processes window context menu:

- Terminate Process		 The selected process is terminated.

Other processes maintain their existing state (suspended or running).
Processes window context menu:

- Detach when debugging stops		 Toggles the behavior of Debug, Stop Debugging for the selected process:

- Checked: The debugger detaches from the process.
- Cleared: The process is terminated.

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See Also

Specify Symbol (.pdb) and Source Files
Attach to Running Processes
Navigating through Code with the Debugger
Just-In-Time Debugging
Debug Multithreaded Applications