object->ref_count > 0 Assertion failures when using webkitgtk - webkit

Question

I'm experimenting with an app that creates a tray menu. One of the tray menu items creates a window that connects to a login service. However, I'm getting assertion failures despite the fact that it otherwise appears to work. I must be doing something simple that is wrong, but what?
The below program demonstrates the problem.
test.cpp
#include <gtk/gtk.h>
#include <webkit/webkit.h>
#include <stdlib.h>
int main(int argc, char* argv[])
{
GtkWidget * web_window = NULL;
WebKitWebView * web_view = NULL;
gtk_init(0L, 0L);
if (web_window = gtk_window_new(GTK_WINDOW_TOPLEVEL)){
//g_object_ref(G_OBJECT(web_window));
gtk_window_set_default_size(GTK_WINDOW(web_window), 800, 600);
g_signal_connect(web_window, "delete_event", G_CALLBACK(gtk_widget_hide_on_delete), NULL);
if (web_view = WEBKIT_WEB_VIEW(webkit_web_view_new())){
//g_object_ref(G_OBJECT(web_view));
gtk_window_set_title(GTK_WINDOW(web_window), "Web View Test");
gtk_container_add(GTK_CONTAINER(web_window), GTK_WIDGET(web_view));
webkit_web_view_load_uri(web_view, "http://www.google.com/");
gtk_widget_grab_focus(GTK_WIDGET(web_view));
gtk_widget_show_all(web_window);
gtk_window_present(GTK_WINDOW(web_window));
gtk_main();
}
else
printf("Failed to create WebView\n");
}
return 0;
}
Compiled with:
g++ test.cpp $(pkg-config --cflags --libs webkitgtk-3.0) $(pkg-config --cflags --libs gtk+-3.0)
After the window is opened and the URL is loaded I see these assertion failures:
(a.out:20179): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(a.out:20179): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
When I then click the close button (which should hide the window) I then see these assertion failures:
(a.out:20179): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(a.out:20179): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
As you can see I tried adding ref counts to the web_window and web_view to see if that was where the problem is, but it made no difference.
Turning on G_DEBUG=fatal-warnings produced a core dump which I backtraced with gdb below.
Program terminated with signal SIGTRAP, Trace/breakpoint trap.
#0 0x00007fdd04662c13 in g_logv () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
(gdb) bt
#0 0x00007fdd04662c13 in g_logv () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#1 0x00007fdd04662d72 in g_log () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007fdd090c9aea in g_object_ref ()
from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#3 0x00007fdd090de05f in g_signal_emit_valist ()
from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4 0x00007fdd090dece2 in g_signal_emit ()
from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5 0x00007fdd095345e6 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#6 0x00007fdd0953609a in gtk_style_context_invalidate ()
from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#7 0x00007fdd09537e4c in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#8 0x00007fdd090c9dba in g_object_unref ()
from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#9 0x00007fdd08440133 in derefGPtr<_GtkStyleContext> (ptr=<optimized out>)
at ../Source/WTF/wtf/gobject/GRefPtr.h:235
#10 ~GRefPtr (this=0x7ffd0e22c3d0, __in_chrg=<optimized out>)
at ../Source/WTF/wtf/gobject/GRefPtr.h:70
#11 WebCore::styleColor (themePart=themePart#entry=WebCore::Entry,
state=state#entry=(GTK_STATE_FLAG_SELECTED | GTK_STATE_FLAG_FOCUSED),
colorType=colorType#entry=WebCore::StyleColorForeground)
at ../Source/WebCore/platform/gtk/RenderThemeGtk3.cpp:1098
#12 0x00007fdd084401f5 in WebCore::RenderThemeGtk::platformActiveSelectionForegr---Type <return> to continue, or q <return> to quit---
oundColor (this=<optimized out>)
at ../Source/WebCore/platform/gtk/RenderThemeGtk3.cpp:1121
#13 0x00007fdd07dba689 in WebCore::RenderTheme::activeSelectionForegroundColor
(this=0x7fdcf40e2870) at ../Source/WebCore/rendering/RenderTheme.cpp:567
#14 0x00007fdd07d6e521 in WebCore::RenderObject::selectionColor (
this=0x7fdc811b4738, colorProperty=335)
at ../Source/WebCore/rendering/RenderObject.cpp:1462
#15 0x00007fdd07d6e55e in WebCore::RenderObject::selectionForegroundColor (
this=this#entry=0x7fdc811b4738)
at ../Source/WebCore/rendering/RenderObject.cpp:1469
#16 0x00007fdd07de27c4 in WebCore::computeTextSelectionPaintStyle (
textPaintStyle=..., renderer=..., lineStyle=..., paintInfo=...,
paintSelectedTextOnly=#0x7ffd0e22c5f1: false,
paintSelectedTextSeparately=#0x7ffd0e22c5f2: false,
selectionShadow=#0x7ffd0e22c628: 0x0)
at ../Source/WebCore/rendering/TextPaintStyle.cpp:127
#17 0x00007fdd07c5265a in WebCore::InlineTextBox::paint (this=0x1956f60,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/InlineTextBox.cpp:575
#18 0x00007fdd07c4bc91 in WebCore::InlineFlowBox::paint (
this=this#entry=0x1956fc0, paintInfo=..., paintOffset=..., lineTop=...,
lineTop#entry=..., lineBottom=..., lineBottom#entry=...)
at ../Source/WebCore/rendering/InlineFlowBox.cpp:1162
---Type <return> to continue, or q <return> to quit---
#19 0x00007fdd07dd46c1 in WebCore::RootInlineBox::paint (this=0x1956fc0,
paintInfo=..., paintOffset=..., lineTop=..., lineBottom=...)
at ../Source/WebCore/rendering/RootInlineBox.cpp:210
#20 0x00007fdd07d4252e in WebCore::RenderLineBoxList::paint (
this=0x7fdc811b62e0, renderer=0x7fdc811b6240, paintInfo=...,
paintOffset=...) at ../Source/WebCore/rendering/RenderLineBoxList.cpp:265
#21 0x00007fdd07c59759 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc811b6240, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2373
#22 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b6240, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#23 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b6240,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#24 0x00007fdd07c42b4c in WebCore::InlineElementBox::paint (this=0x195b4c0,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/InlineElementBox.cpp:88
#25 0x00007fdd07c4bc91 in WebCore::InlineFlowBox::paint (
this=this#entry=0x195b500, paintInfo=..., paintOffset=..., lineTop=...,
lineTop#entry=..., lineBottom=..., lineBottom#entry=...)
at ../Source/WebCore/rendering/InlineFlowBox.cpp:1162
#26 0x00007fdd07dd46c1 in WebCore::RootInlineBox::paint (this=0x195b500,
---Type <return> to continue, or q <return> to quit---
paintInfo=..., paintOffset=..., lineTop=..., lineBottom=...)
at ../Source/WebCore/rendering/RootInlineBox.cpp:210
#27 0x00007fdd07d4252e in WebCore::RenderLineBoxList::paint (
this=0x7fdc811b63a0, renderer=0x7fdc811b6300, paintInfo=...,
paintOffset=...) at ../Source/WebCore/rendering/RenderLineBoxList.cpp:265
#28 0x00007fdd07c59759 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc811b6300, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2373
#29 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b6300, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#30 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b6300,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#31 0x00007fdd07c5988a in WebCore::RenderBlock::paintChild (
this=this#entry=0x7fdc811b63c0, child=..., paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=usePrintRect#entry=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2423
#32 0x00007fdd07c59b72 in WebCore::RenderBlock::paintChildren (
this=0x7fdc811b63c0, paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2393
#33 0x00007fdd07c59730 in WebCore::RenderBlock::paintContents (
---Type <return> to continue, or q <return> to quit---
this=this#entry=0x7fdc811b63c0, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2386
#34 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b63c0, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#35 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b63c0,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#36 0x00007fdd07c5988a in WebCore::RenderBlock::paintChild (
this=this#entry=0x7fdc811b69c0, child=..., paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=usePrintRect#entry=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2423
#37 0x00007fdd07c59b72 in WebCore::RenderBlock::paintChildren (
this=0x7fdc811b69c0, paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2393
#38 0x00007fdd07c59730 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc811b69c0, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2386
#39 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b69c0, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#40 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b69c0,
---Type <return> to continue, or q <return> to quit---
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#41 0x00007fdd07c5988a in WebCore::RenderBlock::paintChild (
this=this#entry=0x7fdc811b6a80, child=..., paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=usePrintRect#entry=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2423
#42 0x00007fdd07c59b72 in WebCore::RenderBlock::paintChildren (
this=0x7fdc811b6a80, paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2393
#43 0x00007fdd07c59730 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc811b6a80, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2386
#44 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b6a80, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#45 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b6a80,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#46 0x00007fdd07c5988a in WebCore::RenderBlock::paintChild (
this=this#entry=0x7fdc811b6b40, child=..., paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=usePrintRect#entry=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2423
---Type <return> to continue, or q <return> to quit---
#47 0x00007fdd07c59b72 in WebCore::RenderBlock::paintChildren (
this=0x7fdc811b6b40, paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2393
#48 0x00007fdd07c59730 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc811b6b40, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2386
#49 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc811b6b40, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#50 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc811b6b40,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#51 0x00007fdd07c5988a in WebCore::RenderBlock::paintChild (
this=this#entry=0x7fdc98144540, child=..., paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=usePrintRect#entry=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2423
#52 0x00007fdd07c59b72 in WebCore::RenderBlock::paintChildren (
this=0x7fdc98144540, paintInfo=..., paintOffset=...,
paintInfoForChild=..., usePrintRect=false)
at ../Source/WebCore/rendering/RenderBlock.cpp:2393
#53 0x00007fdd07c59730 in WebCore::RenderBlock::paintContents (
this=this#entry=0x7fdc98144540, paintInfo=..., paintOffset=...)
---Type <return> to continue, or q <return> to quit---
at ../Source/WebCore/rendering/RenderBlock.cpp:2386
#54 0x00007fdd07c6a473 in WebCore::RenderBlock::paintObject (
this=0x7fdc98144540, paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2509
#55 0x00007fdd07c57135 in WebCore::RenderBlock::paint (this=0x7fdc98144540,
paintInfo=..., paintOffset=...)
at ../Source/WebCore/rendering/RenderBlock.cpp:2186
#56 0x00007fdd07d15c74 in WebCore::RenderLayer::paintForegroundForFragmentsWithPhase (this=this#entry=0x193c340,
phase=phase#entry=WebCore::PaintPhaseForeground, layerFragments=...,
context=context#entry=0x7ffd0e22e7c0, localPaintingInfo=...,
paintBehavior=paintBehavior#entry=0,
subtreePaintRootForRenderer=subtreePaintRootForRenderer#entry=0x0)
at ../Source/WebCore/rendering/RenderLayer.cpp:4477
#57 0x00007fdd07d1aad6 in WebCore::RenderLayer::paintForegroundForFragments (
this=this#entry=0x193c340, layerFragments=...,
context=context#entry=0x7ffd0e22e7c0,
transparencyLayerContext=transparencyLayerContext#entry=0x7ffd0e22e7c0,
transparencyPaintDirtyRect=...,
haveTransparency=haveTransparency#entry=false, localPaintingInfo=...,
paintBehavior=paintBehavior#entry=0,
subtreePaintRootForRenderer=subtreePaintRootForRenderer#entry=0x0,
selectionOnly=selectionOnly#entry=false,
---Type <return> to continue, or q <return> to quit---
forceBlackText=forceBlackText#entry=false)
at ../Source/WebCore/rendering/RenderLayer.cpp:4441
#58 0x00007fdd07d27406 in WebCore::RenderLayer::paintLayerContents (
this=this#entry=0x193c340, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:4162
#59 0x00007fdd07d27a7f in WebCore::RenderLayer::paintLayerContentsAndReflection
(this=this#entry=0x193c340, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=paintFlags#entry=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:3858
#60 0x00007fdd07d283d9 in WebCore::RenderLayer::paintLayer (
this=this#entry=0x193c340, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=paintFlags#entry=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:3839
#61 0x00007fdd07d29d02 in WebCore::RenderLayer::paintList (this=0x192bcd0,
list=0x7fdc8115a830, context=0x7ffd0e22e7c0, paintingInfo=...,
paintFlags=224) at ../Source/WebCore/rendering/RenderLayer.cpp:4255
#62 0x00007fdd07d27520 in WebCore::RenderLayer::paintLayerContents (
this=this#entry=0x192bcd0, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:4173
#63 0x00007fdd07d27a7f in WebCore::RenderLayer::paintLayerContentsAndReflection
(this=this#entry=0x192bcd0, context=context#entry=0x7ffd0e22e7c0,
---Type <return> to continue, or q <return> to quit---
paintingInfo=..., paintFlags=paintFlags#entry=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:3858
#64 0x00007fdd07d283d9 in WebCore::RenderLayer::paintLayer (
this=this#entry=0x192bcd0, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=paintFlags#entry=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:3839
#65 0x00007fdd07d29d02 in WebCore::RenderLayer::paintList (this=0x180d8f0,
list=0x7fdc8115a840, context=0x7ffd0e22e7c0, paintingInfo=...,
paintFlags=224) at ../Source/WebCore/rendering/RenderLayer.cpp:4255
#66 0x00007fdd07d27520 in WebCore::RenderLayer::paintLayerContents (
this=this#entry=0x180d8f0, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=224)
at ../Source/WebCore/rendering/RenderLayer.cpp:4173
#67 0x00007fdd07d27a7f in WebCore::RenderLayer::paintLayerContentsAndReflection
(this=this#entry=0x180d8f0, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=paintFlags#entry=0)
at ../Source/WebCore/rendering/RenderLayer.cpp:3858
#68 0x00007fdd07d283d9 in WebCore::RenderLayer::paintLayer (
this=this#entry=0x180d8f0, context=context#entry=0x7ffd0e22e7c0,
paintingInfo=..., paintFlags=paintFlags#entry=0)
at ../Source/WebCore/rendering/RenderLayer.cpp:3839
#69 0x00007fdd07d2867e in WebCore::RenderLayer::paint (
this=this#entry=0x180d8f0, context=context#entry=0x7ffd0e22e7c0,
---Type <return> to continue, or q <return> to quit---
damageRect=..., paintBehavior=0,
subtreePaintRoot=subtreePaintRoot#entry=0x0, region=region#entry=0x0,
paintFlags=paintFlags#entry=0)
at ../Source/WebCore/rendering/RenderLayer.cpp:3623
#70 0x00007fdd07bdda1d in WebCore::FrameView::paintContents (
this=0x7fdcf40dd800, p=0x7ffd0e22e7c0, rect=...)
at ../Source/WebCore/page/FrameView.cpp:3507
#71 0x00007fdd082ef894 in WebCore::ScrollView::paint (this=0x7fdcf40dd800,
context=0x7ffd0e22e7c0, rect=...)
at ../Source/WebCore/platform/ScrollView.cpp:1162
#72 0x00007fdd074bc3bb in paintWebView (dirtyRegion=..., frame=0x7fdcf40f5c00,
webView=0x17dc440)
at ../Source/WebKit/gtk/WebCoreSupport/ChromeClientGtk.cpp:588
#73 WebKit::ChromeClient::paint (this=0x173da00)
at ../Source/WebKit/gtk/WebCoreSupport/ChromeClientGtk.cpp:631
#74 0x00007fdd075c67b1 in WebCore::ThreadTimers::sharedTimerFiredInternal (
this=0x7fdcf4108f50) at ../Source/WebCore/platform/ThreadTimers.cpp:132
#75 0x00007fdd075dea62 in WebCore::sharedTimerTimeoutCallback ()
at ../Source/WebCore/platform/gtk/SharedTimerGtk.cpp:49
#76 0x00007fdd0465c703 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#77 0x00007fdd0465bce5 in g_main_context_dispatch ()
from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#78 0x00007fdd0465c048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
---Type <return> to continue, or q <return> to quit---
#79 0x00007fdd0465c30a in g_main_loop_run ()
from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#80 0x00007fdd094a6e25 in gtk_main ()
from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#81 0x0000000000400d52 in main ()

Answer 1

It's natural to think that you are doing something wrong but when it comes to GLib-GObject-CRITICAL failures the issue has little, if anything, to do with your code and more to do with the GNOME ecosystem.
For instance, I can reproduce this issue with both well established projects and barebone GTK+ 3 applications in C++/Python by running them on older versions of GNOME but the issue goes away with a recent version of GNOME.
Since I didn't modify the code between tests then the code must be fine.
If you develop with planned obsolescence in mind, forcing users of your software to upgrade GNOME in order to use it then this is probably non-issue nowadays.
But if you are developing against an older version of GNOME or for some reason this (or a new) GLib-GObject-CRITICAL failure is present with a recent version of GNOME then the easiest solution is to filter it out.
Personally, I would unit test where applicable and ignore the following GLib-GObject-CRITICAL failure patterns:
object->ref_count > 0
source->priv != NULL