Simple GUIPlugin causes Segfault when closing gzclient

[osrf-migration]

Original report (archived issue) by MarcZofka (Bitbucket: GzMRZ).

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Dear colleagues,

i have noticed a strange bug in a GUIPlugin, i have implemented. When starting gzserver and gzclient separately, the plugin causes a segfault in the gzserver process during closing the client:

#!c++


Thread 1 "gzclient" received signal SIGSEGV, Segmentation fault.
0x0000000000ba70c0 in ?? ()
(gdb) 
(gdb) bt
#0  0x0000000000ba70c0 in ?? ()
#1  0x00007ffff77411c0 in gazebo::gui::RenderWidget::~RenderWidget() () from /usr/lib/x86_64-linux-gnu/libgazebo_gui.so.7
#2  0x00007ffff77412f9 in gazebo::gui::RenderWidget::~RenderWidget() () from /usr/lib/x86_64-linux-gnu/libgazebo_gui.so.7
#3  0x00007ffff76dadd1 in gazebo::gui::MainWindow::closeEvent(QCloseEvent*) () from /usr/lib/x86_64-linux-gnu/libgazebo_gui.so.7
#4  0x00007ffff53ab8d0 in QWidget::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#5  0x00007ffff578f9b3 in QMainWindow::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#6  0x00007ffff5354fdc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#7  0x00007ffff535bf16 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#8  0x00007ffff720590d in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9  0x00007ffff53a8131 in QWidgetPrivate::close_helper(QWidgetPrivate::CloseMode) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#10 0x00007ffff53c7c56 in QApplication::x11ClientMessage(QWidget*, _XEvent*, bool) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#11 0x00007ffff53d7e32 in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#12 0x00007ffff5402542 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#13 0x00007ffff1f10197 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007ffff1f103f0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00007ffff1f1049c in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#16 0x00007ffff72362ae in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#17 0x00007ffff5402616 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#18 0x00007ffff720418f in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#19 0x00007ffff72044f5 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#20 0x00007ffff720a4b9 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#21 0x00007ffff76b7873 in gazebo::gui::run(int, char**) () from /usr/lib/x86_64-linux-gnu/libgazebo_gui.so.7
#22 0x00000000004013aa in ?? ()
#23 0x00007ffff6536830 in __libc_start_main (main=0x401390, argc=2, argv=0x7fffffffd2a8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffd298) at ../csu/libc-start.c:291
#24 0x0000000000401459 in _start ()
(gdb) 

I have trimmed my plugin down to a very minimalistic version, but the segfault still appears in some cases (about 50%):

#!c++

#ifndef GAZEBO_GUI_SCENE_GRAPH_PLUGIN_H_INCLUDED
#define GAZEBO_GUI_SCENE_GRAPH_PLUGIN_H_INCLUDED

// System Includes
#include <memory>

// Gazebo Includes
#include <gazebo/gui/GuiPlugin.hh>

// See: https://bugreports.qt-project.org/browse/QTBUG-22829
#ifndef Q_MOC_RUN
# include <gazebo/transport/transport.hh>
# include <gazebo/gui/gui.hh>
#endif

namespace gazebo
{

class GAZEBO_VISIBLE GUISceneGraphPlugin : public GUIPlugin
{
  Q_OBJECT

public:
  //! Constructor.
  GUISceneGraphPlugin();
  //! Destructor.
  virtual ~GUISceneGraphPlugin();

  //! This function is only called when a GUI plugin is loaded from an SDF file. This function is
  //! not called when a GUI plugin is loaded via a gui.ini file.
  //! \param[in] _sdf Pointer the the SDF element of the plugin. This is the plugin SDF,
  //! <plugin ...>, and its children.
  void Load(sdf::ElementPtr sdf);

private:

  float m_clipping_min;
  float m_clipping_max;

};

} // end of ns gazebo
#endif // GAZEBO_GUI_SCENE_GRAPH_PLUGIN_H_INCLUDED

and the definition in:

#!c++

// Gazebo Includes
#include <gazebo/common/common.hh>
#include <gazebo/rendering/rendering.hh>
#include <gazebo/msgs/vector3d.pb.h>

// Ignition Includes
#include <ignition/math/Vector3.hh>

// Ogre Includes
#include <OGRE/OgreManualObject.h>
#include <OGRE/OgreException.h>

// Std Includes
#include <list>

#include "GUISceneGraphPlugin.hh"

namespace gazebo {

// Register this plugin with the simulator
GZ_REGISTER_GUI_PLUGIN(GUISceneGraphPlugin)

/////////////////////////////////////////////////
GUISceneGraphPlugin::GUISceneGraphPlugin()
  : GUIPlugin()
  , m_clipping_min(5)
  , m_clipping_max(1000)
{
}

/////////////////////////////////////////////////
GUISceneGraphPlugin::~GUISceneGraphPlugin()
{}

/////////////////////////////////////////////////
void GUISceneGraphPlugin::Load(sdf::ElementPtr sdf)
{
  gzmsg << "(GUISceneGraphPlugin) Load() called." << std::endl;
}

} // end of ns gazebo

My exemplary world file is as follows:

#!c++

?xml version="1.0" ?>
<sdf version="1.5">
  <world name="default">
    <gui>
        <plugin name="sampleplugin" filename="libGUISceneGraphPlugin.so"/>
    </gui>

    <!-- A global light source -->
    <include>
      <uri>model://sun</uri>
    </include>
    <!-- A ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>
  </world>
</sdf>

I tried to find some evidences on google, but i merely found an entry on the gazebo answers list, where somebody seems to have the same problem: Gazebo Anwers

It seems to be a problem with GUI plugins in general, so I would be happy if anybody has an idea, why this strange segfault appears.

Best regards!

[osrf-migration]

Original comment by MarcZofka (Bitbucket: GzMRZ).

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• Edited issue description

[osrf-migration]

Original comment by MarcZofka (Bitbucket: GzMRZ).

---

• Edited issue description

[osrf-migration]

Original comment by Jose Luis Rivero (Bitbucket: Jose Luis Rivero, GitHub: j-rivero).

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could it be related to issue #2133? Can you verify if the problem is also present in gazebo8? Please note that there is a new parameter called --gui-client-plugin to load the GUI plugins.

[osrf-migration]

Original comment by MarcZofka (Bitbucket: GzMRZ).

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Hi,

your assumption seems possible: In the minimalistic version (see above) of my gui plugin i had several gzclient runs, where i have not seen the black widget, which typically should appear when no exact size of the widget is defined in the plugin. In the full version of my plugin, where i have a complex layout with text fields, checkboxes and so on i cannot confirm the behavior.

Unfortunately i have no possibility to validate the repeatability of this bug in gz8. Is the parameter, mentioned before, also necessary in gz7?

Best regards!

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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You state that the plugin causes a seg-fault in gzserver, but the backtrace says gzclient.

I'll see if I can find time to try to reproduce this.

[osrf-migration]

Original comment by MarcZofka (Bitbucket: GzMRZ).

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Hi,

yeah you are right: the segfault appears in the gzclient. Could anyone reproduce the error?

best regards!