I sometimes hit this Glib CRITICAL when closing a page. Although it comes from a Release build it looks like the WebKitWebPage is released too early. (WebKitWebProcess:3793): GLib-GObject-WARNING **: invalid uninstantiatable type `(null)' in cast to `WebKitWebPage' (WebKitWebProcess:3793): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `(null)' (WebKitWebProcess:3793): GLib-GObject-CRITICAL **: g_signal_emit_valist: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed (gdb) bt #0 g_log (log_domain=0x7f46106d9f70 "GLib-GObject", log_level=G_LOG_LEVEL_CRITICAL, format=0x7f461042a7ac "%s: assertion `%s' failed") at gmessages.c:1009 #1 0x00007f46103a3240 in g_return_if_fail_warning (log_domain=0x7f46106d9f70 "GLib-GObject", pretty_function=0x7f46106db1d0 "g_signal_emit_valist", expression=0x7f46106da100 "G_TYPE_CHECK_INSTANCE (instance)") at gmessages.c:1019 #2 0x00007f46106c1a7c in g_signal_emit_valist (instance=0x3a79f00, signal_id=181, detail=0, var_args=0x7ffffe6f9eb8) at gsignal.c:3105 #3 0x00007f46106c3184 in g_signal_emit (instance=0x3a79f00, signal_id=181, detail=0) at gsignal.c:3384 #4 0x00007f461394cb6e in WebKit::InjectedBundlePageLoaderClient::didFinishDocumentLoadForFrame(WebKit::WebPage*, WebKit::WebFrame*, WTF::RefPtr<WebKit::APIObject>&) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #5 0x00007f4613983ca8 in WebKit::WebFrameLoaderClient::dispatchDidFinishDocumentLoad() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #6 0x00007f4613f80801 in WebCore::FrameLoader::finishedParsing() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #7 0x00007f4613f80a98 in WebCore::FrameLoader::stopLoading(WebCore::UnloadEventPolicy) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #8 0x00007f4613f80d62 in WebCore::FrameLoader::closeURL() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #9 0x00007f4613f80db8 in WebCore::FrameLoader::detachFromParent() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #10 0x00007f46139a653f in WebKit::WebPage::close() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #11 0x00007f46139d0361 in WebKit::WebPage::didReceiveWebPageMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #12 0x00007f4614e01de5 in CoreIPC::MessageReceiverMap::dispatchMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #13 0x00007f46139af505 in WebKit::WebProcess::didReceiveMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #14 0x00007f4614dfbd43 in CoreIPC::Connection::dispatchMessage(WTF::PassOwnPtr<CoreIPC::MessageDecoder>) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #15 0x00007f4614dfbeaf in CoreIPC::Connection::dispatchOneMessage() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #16 0x00007f4614ce77b7 in WebCore::RunLoop::performWork() () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #17 0x00007f4614cf22f9 in WebCore::RunLoop::queueWork(WebCore::RunLoop*) () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #18 0x00007f461039b5fb in g_idle_dispatch (source=0x7f45a8001e00, callback=0x7f4614cf22f0 <WebCore::RunLoop::queueWork(WebCore::RunLoop*)>, user_data=0x7f4602bb4c98) at gmain.c:5205 #19 0x00007f4610398e79 in g_main_dispatch (context=0x9ed570) at gmain.c:3054 #20 0x00007f4610399bde in g_main_context_dispatch (context=0x9ed570) at gmain.c:3630 #21 0x00007f4610399dce in g_main_context_iterate (context=0x9ed570, block=1, dispatch=1, self=0xa2fb50) at gmain.c:3701 #22 0x00007f461039a1fe in g_main_loop_run (loop=0xa5d1c0) at gmain.c:3895 #23 0x00007f4613939d9a in WebProcessMainGtk () from /opt/gnome3/lib64/libwebkit2gtk-3.0.so.0 #24 0x00007f460fb93a55 in __libc_start_main (main=0x4008b0 <main>, argc=2, ubp_av=0x7ffffe6fa918, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffffe6fa908) at libc-start.c:260 #25 0x00000000004008e1 in _start ()
This is probably a dupe of bug #112334 that has a patch waiting review.
Makes sense to me. *** This bug has been marked as a duplicate of bug 112334 ***