Object reference incorrectly held at CefShutdown

[joeludwig]

I'm getting this error/crash at shutdown:

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[0112/115346.263:FATAL:shutdown_checker.cc(52)] Check failed: !IsCefShutdown(). Object reference incorrectly held at CefShutdown


This seems to be a browser object that was created by a window.open call in Javascript. The open call was to a custom protocol (steam:// in this case, but I don't think it matters.) In OnProtocolExecution I call:

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browser->GetHost()->CloseBrowser( true );


And then return without keeping a reference to the browser. I'm pretty sure I don't have reference to the browser anywhere on my side. Yet in CefShutdown there's one browser object still hanging around with a reference to it.

Is there some stronger way to close a browser than the above? Is there some way to handle custom protocols without ever opening a window in the first place?

[Czarek]

You should check stack trace. See https://bitbucket.org/chromiumembedded/ ... -cefrefptr

[joeludwig]

I saw that issue, but don't seem to have a stack track in the debug output or the log file. Is that something I have to turn on?


Joe

[Czarek]

You have to run a debugger to print backtrace. You should download debug symbols from where you've obtained binaries.

[Tonygeek]

I have a similar problem but am unaware of what can I do to narrow it down.
I get this message:

[0115/061854.595:FATAL:browser_main.cc(215)] Check failed: global_request_context_->HasOneRef().

and this call stack:

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    libcef.dll!logging::LogMessage::~LogMessage() Line 950   C++
    libcef.dll!CefBrowserMainParts::PostMainMessageLoopRun() Line 216   C++
    libcef.dll!content::BrowserMainLoop::ShutdownThreadsAndCleanUp() Line 1071   C++
    libcef.dll!content::BrowserMainRunnerImpl::Shutdown() Line 179   C++
    libcef.dll!CefMainDelegate::ShutdownBrowser() Line 812   C++
    libcef.dll!CefContext::FinalizeShutdown() Line 632   C++
    libcef.dll!CefContext::Shutdown() Line 488   C++
    libcef.dll!CefShutdown() Line 272   C++
   Win32CEFSimpleApp.exe!CefShutdown() Line 121   C++
    Win32CEFSimpleApp.exe!wWinMain(HINSTANCE__ * hInstance=0x01310000, HINSTANCE__ * hPrevInstance=0x00000000, wchar_t * lpCmdLine=0x00c729c8, int nCmdShow=10) Line 93   C++

cefsimple and cefclient work fine, it is only my app that exhibits this. However the code is mostly copied from cefsimple and the main difference is in window creation ( I call CreateBrowser() from WM_CREATE).

[Tonygeek]

Sorry, my bad.
In my case I had a member variable in my client:

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CefRefPtr<CefBrowser> browser;

but I forgot to null it before calling CefQuitMessageLoop().

[joeludwig]

You have to run a debugger to print backtrace. You should download debug symbols from where you've obtained binaries.

I have symbols (and even source) for the CEF build I'm using. I am running in the debugger.

I have a backtrace for the assert itself. That issue makes it sound like I should have a backtrace for either where the ref was incremented or where the browser was created. I don't have either of those. Is that a thing, or is trying to trace through the refs and unrefs of all browsers the best I can do?


Joe

[Czarek]

The stack trace should point you to an object that fails. Then you have to fix usage of that object in your app.

[joeludwig]

The stack trace should point you to an object that fails. Then you have to fix usage of that object in your app.

When you say "the stack trace", you mean the stack trace when the fatal log message is emitted at shutdown? That's the only one I've seen.

That pointed me at a browser object I didn't create that was handed to me in OnProtocolExecution, which I then kept no reference to. Here's my entire interaction with that browser object:

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void CAardvarkResourceRequestHandler::OnProtocolExecution( CefRefPtr<CefBrowser> browser,
   CefRefPtr<CefFrame> frame,
   CefRefPtr<CefRequest> request,
   bool& allow_os_execution )
{
   std::string url = request->GetURL();
   allow_os_execution = tools::stringIsPrefix( "pluto://", url )
      || tools::stringIsPrefix( "steam://", url )
      || tools::stringIsPrefix( "aardvark://", url );

   // we never want to keep these dead windows around
   browser->GetHost()->CloseBrowser( true );
}


[Czarek]

Do not close browser from within callbacks. Use CefPostTaskDelayed or similar to close after the callback completes.