PDA

View Full Version : QWidget::show () segmentation fault


Umar Said
21st September 2007, 05:04
Hi all,

I am using Qt3 to develop GUI program. In my program, I provide some toolbars and when user click on it, a window will pop up. But there is a strange behaviour happened. When I clicked on the toolbar, the program crashed and showed "segmentation fault" error. By using gdb, I found out that this happened whenever QWidget::show() executed.

The error happened when I use Qt3 library from my own compilation and running on Debian etch. When I use the Qt3 library provided by Debian Etch, the problem occurred occasionally and unpredictable. But when I use Qt3 library from my own compilation and running on Ubuntu Breezy, the error never occurred.

Has anyone experience problem like mine? Any hints will be appreciated.

Umar Said
marcel
21st September 2007, 06:54
What else happens when the widget is shown?
You should post some code.
Make sure you don't modify that widget from other threads.
winux
21st September 2007, 07:28
When I was coding on two distros, I made sure that the versions and releases are the same. If there is a difference, even a slight difference, I usually recreate project and rebuild project. You also need to check the documentation of the two, there may be changes, and your implementation somehow causes the segmentation fault.
Umar Said
22nd September 2007, 10:09
Thanks very much for all your reply.

I intended to put an attachment of my source in tar.bz2, but due to my very very bad internet connection, I post them here. Sorry for the long codes.

The main problem is displaying dialog CreateHull.ui when I click on a toolbar. Below is the source code of it. I hope you can reproduce the error. Maybe later when my internet connection get better, I will attach the source in tar.bz2 format.

I compile and run the code in two different computer. One on Debian Etch using libqt3-mt 3.3.7-4 and gcc version 3.3.6, while the other on Ubuntu Breezy using my own compiled qt3 3.3.7 and gcc 4.0.2. The program run normal on Ubuntu, when I click the toolbar, the CreateHull dialog pop up. But when I run the same program on Debian, the program exited with segmentation error.

CreateHullBase.ui

<!DOCTYPE UI><UI version="3.3" stdsetdef="1">
<class>CreateHullBase</class>
<widget class="QDialog">
<property name="name">
<cstring>CreateHullBase</cstring>
</property>
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>201</width>
<height>122</height>
</rect>
</property>
<property name="caption">
<string>Outer Hull</string>
</property>
<property name="icon">
<pixmap>image0</pixmap>
</property>
<grid>
<property name="name">
<cstring>unnamed</cstring>
</property>
<widget class="QLayoutWidget" row="0" column="0">
<property name="name">
<cstring>layout7</cstring>
</property>
<grid>
<property name="name">
<cstring>unnamed</cstring>
</property>
<widget class="QLineEdit" row="0" column="1">
<property name="name">
<cstring>txtBreadth</cstring>
</property>
</widget>
<widget class="QLineEdit" row="1" column="1">
<property name="name">
<cstring>txtDepth</cstring>
</property>
</widget>
<widget class="QLabel" row="0" column="0">
<property name="name">
<cstring>textLabel1</cstring>
</property>
<property name="text">
<string>Breadth :</string>
</property>
</widget>
<widget class="QLabel" row="1" column="0">
<property name="name">
<cstring>textLabel2</cstring>
</property>
<property name="text">
<string>Depth :</string>
</property>
</widget>
</grid>
</widget>
<spacer row="1" column="0">
<property name="name">
<cstring>spacer6</cstring>
</property>
<property name="orientation">
<enum>Vertical</enum>
</property>
<property name="sizeType">
<enum>Expanding</enum>
</property>
<property name="sizeHint">
<size>
<width>20</width>
<height>20</height>
</size>
</property>
</spacer>
<widget class="QLayoutWidget" row="2" column="0">
<property name="name">
<cstring>layout8</cstring>
</property>
<hbox>
<property name="name">
<cstring>unnamed</cstring>
</property>
<spacer>
<property name="name">
<cstring>spacer7</cstring>
</property>
<property name="orientation">
<enum>Horizontal</enum>
</property>
<property name="sizeType">
<enum>Expanding</enum>
</property>
<property name="sizeHint">
<size>
<width>20</width>
<height>20</height>
</size>
</property>
</spacer>
<widget class="QPushButton">
<property name="name">
<cstring>btnCreate</cstring>
</property>
<property name="text">
<string>&amp;Create</string>
</property>
<property name="accel">
<string>Alt+C</string>
</property>
</widget>
<widget class="QPushButton">
<property name="name">
<cstring>btnClose</cstring>
</property>
<property name="text">
<string>Close</string>
</property>
</widget>
</hbox>
</widget>
</grid>
</widget>
<images>
<image name="image0">
<data format="PNG" length="477">89504e470d0a1a0a0000000d49484452000000100000001008 060000001ff3ff61000001a449444154789c9d9331481b6118 869f8bcde19004940e1d345320d2e51c6d860ec5160411a4a4 118a09073786cc0117c9e2261a220ebd9fd0a11a101c840ca9 0856316d37bb58d2de620669d586a61789e291eb76782647b5 dff4bfffffbecffff1c12701944a25bbd56a71dfd2344d9274 5db763b1189148e45e61c330a856abf800cfb0100245519065 1945511042605916ed76dbc93cf0fa4108c1d6c612d5f72bc8 721fed8bdfcc6a592ccb22994c3a3e9f17209fcfb3f67685be ce4fae7e7dc077f985d585690a8582cbe77420cb7217646078 9cc6d1bca343c17e6ab55a6f00c08f3915eba4eee8a1e20e83 8fe779579861e2d9087fcc4ba2d1a837c03aa9737dfcdd65d8 fb74c8d3b151b6d73516dfec934ea75def9e3300c8e5727cfe 7606402677c0e4cb0ca954ea6e8062bdc9f3a9579c364cd4ec 32e170185555bb7c9e80f317aff97adc00e0e1a3612a950ae5 72b9cbe79ac15071c7397f5cccb0b97be46835bb4c3c1ea7d9 6cf606dcdc854020c093d111afe67a036cdb762e4dd3ec69ee 743a00f8fd7e37c0308cff5aa650288404a0ebbafdafc0ed0a 0683241209e92f6d219098fc3e299c0000000049454e44ae42 6082</data>
</image>
</images>
<connections>
<connection>
<sender>btnClose</sender>
<signal>clicked()</signal>
<receiver>CreateHullBase</receiver>
<slot>accept()</slot>
</connection>
</connections>
<layoutdefaults spacing="6" margin="11"/>
</UI>
jpn
22nd September 2007, 13:54
Could we see the relevant code (not the designed form)? Or run it through a debugger and see backtrace where exactly does it crash.
Umar Said
24th September 2007, 04:46
I have attached the source code. When I compile it using debug config, the backtrace output is below (truncated).



(gdb) bt
#0 0x0809d77f in ?? ()
#1 0x0804d954 in MainWindow::editFind (this=0x8080de8)
at src/MainWindow.cpp:24
#2 0x08055556 in MainWindowBase::qt_invoke (this=0x8080de8, _id=72,
_o=0xbf88858c) at .moc/moc_MainWindowBase.cpp:123
#3 0x08054a17 in MainWindow::qt_invoke (this=0x8080de8, _id=72, _o=0xbf88858c)
at .moc/moc_MainWindow.cpp:77
#4 0xb7a41d4f in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#5 0xb7a427e0 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#6 0xb7df33ea in QAction::activated () from /usr/lib/libqt-mt.so.3
#7 0xb7baad51 in QAction::internalActivation () from /usr/lib/libqt-mt.so.3
#8 0xb7df3152 in QAction::qt_invoke () from /usr/lib/libqt-mt.so.3
#9 0xb7a41d4f in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#10 0xb7dcaee3 in QSignal::signal () from /usr/lib/libqt-mt.so.3


Actually, I also found this kind of error about a year ago when beginning to use Qt. It also happened in Debian Etch. When I compile it, a warning appeared.



/usr/bin/ld: warning: libstdc++.so.6, needed by /usr/share/qt3/lib/libqt-mt.so, may conflict with libstdc++.so.5
Umar Said
27th September 2007, 05:50
I've just find out that on Ubuntu Feisty (7.10), the code also generated error. The Qt I used is libqt3-mt 3.3.8really3.3.7-0ubuntu5.2. Is this Linux or Qt issue? Anybody willing to try it?