Question

I am using the new MessageLoop class introduced in pepper-25 so I can run a background thread with blocking ppapi calls for File IO. Up until now I have been running chrome from visual studio with the flags --single-process and --register-pepper-plugins so I can debug my plugin from within visual studio.

Using these flags I found that the call to PPB_GetInterface get_browser for PPB_MESSAGING_INTERFACE was returning null and after some searching I found this issue which states you must run with the flag --ppapi-out-of-process to get MessageLoop support.

With that flag added get_browser does return a valid interface pointer but I can no longer debug my plugin with the visual studio ide as it cannot attach to the child process that my plugin is run from. Is there anyway to tell it to attach to my plug-in process or a way of running from a single process with support for MessageLoop?

Thanks,
James

Answer 1

To get Visual Studio to attach to child processes automatically, you can use the workarounds described at Can Visual Studio be made to debug child processes like WinDBG?.

A different approach is to use the flags --no-sandbox and --ppapi-startup-dialog when you start Chrome. This will cause a message box to appear with the process id when a plugin process is created. You can then connect the Visual Studio debugger to that process using Debug -> Attach to process… -> pick process id. Of course, you could have attached to the process without the Chrome flags and it’s not automatic, so this really just gives you certainty that you’re attaching to the right process if you have many running at the same time.

A third approach is to use the free Microsoft-provided debugger WinDbg. It is complex and much less user-friendly than the built-in debugger in Visual Studio, but it does have the ability to attach to child processes automatically. Download is available from http://msdn.microsoft.com/en-us/windows/hardware/gg463009.aspx.

As for MessageLoop it will not be supported for in-process plugins. As the issue you link to mentions, developers should move to out-of-process, even if it adds the inconvenience of not being able to attach the Visual Studio debugger automatically without workarounds.