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This page has detailed information to help you debug Chromium on Windows.

 

Note: If you‘ve never built or debugged Chromium on Windows, first read the Windows build instructions.

Before you start Requirements

You can use Visual Studio‘s built-in debugger or WinDBG to debug Chromium. Note that if you are using goma to build, much of this will not work; see .

Optional

So that you can continue to run release versions of the browser — and avoid incompatible profile changes — while you debug, you should use a different profile for your debug Chromium instance from the release build that you use. You can set the profile by modifying the command line used to launch Chromium from the debugger. To do this, go to the Debugging tab of the properties of the chrome project, and set the Command Arguments field to --user-data-dir=c:\tmp\my_debug_profile. (Replace c:\tmp\my_debug_profile with a directory of your choosing.) Another possibility, if you have lots of different checkouts, is to change the path of the shortcut you use for the release build so that it sets the profile.

 

Tools such as ProcessExplorer, Spy++/Winspector Spy, Inspect32, and FileMon may be of use when debugging different parts of Chromium.

 

Multi-process issues

Chromium can be challenging to debug because of its multi-process architecture. When you select Run in the debugger, only the main Browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that‘s not (yet!) being debugged.

There are a number of approaches to solving this problem.

Single-process mode

The easiest way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process to the Command Arguments field in the Debugging tab of the properties of the chrome project. This approach isn‘t perfect because some problems won‘t manifest themselves in this mode. Also, even in single-process mode, worker threads are spawned into new processes.

Tip: By default, when you load the project, Visual Studio may select Browser/browser.exe as the "startup project," and you will notice that chrome.exe is not bolded in the list of projects. If this is the case, then just clicking Debug > Start Debugging will start a different project, and ignore the command line flag you just provided. To change this, right-click the chrome.exe project and choose Set As Startup Project.

Using Image File Execution Options

Using Image File Execution Options (IFEO) will not work,  because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are issues too with the sandbox.

Chrome Debug Log

Enable Chrome debug logging to a file by passing --enable-logging --v=1 command-line flags at startup. Debug builds place the chrome_debug.log file in the out\Debug directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see logging and user data directory details.

Debugging with Visual Studio Attaching to the renderer

You can also attach to the running child processes with the debugger. Select Tools > Attach to Process and click the chrome.exe process you want to attach to. You can now debug the two processes as if they were one.Use  or  to attach to the right processes.

When you are debugging multiple processes, open the Debug > Windows > Processes window to switch between them. 

Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. In this case, you can use the --renderer-startup-dialog command line flag to the browser.Important note: If you use this flag you also have to pass the --no-sandbox flag, since the sandbox will otherwise prevent the renderer from showing a startup dialog. The browser will pass this along to each renderer it starts, which will display a message box as soon as it starts. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you‘re debugging in the renderer.

 

Semi-automatically attaching the debugger to child processes