qtcreator won't run after update to 6.8.2: xcb error

Tom asso

Downloaded and installed Qt 6.8.2 on ubuntu 22.04.3, using online installer.
qtcreator now fails to run:

$ ./qtcreator
qt.qpa.plugin: From 6.5.0, xcb-cursor0 or libxcb-cursor0 is needed to load the Qt xcb platform plugin.
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

libxcb-cursor0 is already installed and up-to-date.
I also just installed libxcb-cursor-dev as advised here, but error is exactly the same.
Any ideas? Thanks!

SGaist

Why ?

Unset it and try again please.

SGaist

Hi,

Start Qt Creator from the command line with the QT_DEBUG_PLUGINS environment variable set to 1 to see exactly why the plug-in loading fails.

Tom asso

@SGaist - Thanks! I see this error message toward the end of the debug output:

qt.core.plugin.loader: QLibraryPrivate::loadPlugin failed on "/home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so" : "Cannot load library /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so: /home/oreilly/Qt6.8/6.8.2/gcc_64/lib/libQt6XcbQpa.so.6: undefined symbol: _Z17lcQpaInputDevicesv, version Qt_6"

Here is the entire debug output:

qt.core.plugin.factoryloader: checking directory path "/home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms" ...
qt.core.plugin.factoryloader: looking at "libqwayland-generic.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqwayland-generic.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland"
        ]
    },
    "archlevel": 1,
    "className": "QWaylandIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("wayland")
qt.core.plugin.factoryloader: looking at "libqxcb.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archlevel": 1,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("xcb")
qt.core.plugin.factoryloader: looking at "libqeglfs.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "archlevel": 1,
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("eglfs")
qt.core.plugin.factoryloader: looking at "libqvkkhrdisplay.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqvkkhrdisplay.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vkkhrdisplay"
        ]
    },
    "archlevel": 1,
    "className": "QVkKhrDisplayIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("vkkhrdisplay")
qt.core.plugin.factoryloader: looking at "libqminimalegl.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "archlevel": 1,
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("minimalegl")
qt.core.plugin.factoryloader: looking at "libqwayland-egl.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqwayland-egl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland-egl"
        ]
    },
    "archlevel": 1,
    "className": "QWaylandEglPlatformIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("wayland-egl")
qt.core.plugin.factoryloader: looking at "libqlinuxfb.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqlinuxfb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "linuxfb"
        ]
    },
    "archlevel": 1,
    "className": "QLinuxFbIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("linuxfb")
qt.core.plugin.factoryloader: looking at "libqoffscreen.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "archlevel": 1,
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("offscreen")
qt.core.plugin.factoryloader: looking at "libqvnc.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "archlevel": 1,
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("vnc")
qt.core.plugin.factoryloader: looking at "libqminimal.so"
qt.core.plugin.loader: Found metadata in lib /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "archlevel": 1,
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 395264
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("minimal")
qt.core.plugin.factoryloader: checking directory path "/home/oreilly/Qt6.8/Tools/QtCreator/bin/platforms" ...
qt.core.library: "/home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so" cannot load: Cannot load library /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so: /home/oreilly/Qt6.8/6.8.2/gcc_64/lib/libQt6XcbQpa.so.6: undefined symbol: _Z17lcQpaInputDevicesv, version Qt_6
qt.core.plugin.loader: QLibraryPrivate::loadPlugin failed on "/home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so" : "Cannot load library /home/oreilly/Qt6.8/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so: /home/oreilly/Qt6.8/6.8.2/gcc_64/lib/libQt6XcbQpa.so.6: undefined symbol: _Z17lcQpaInputDevicesv, version Qt_6"
qt.qpa.plugin: From 6.5.0, xcb-cursor0 or libxcb-cursor0 is needed to load the Qt xcb platform plugin.
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: wayland, xcb, eglfs, vkkhrdisplay, minimalegl, wayland-egl, linuxfb, offscreen, vnc, minimal.

SGaist

Do you have LD_LIBRARY_PATH defined ?

Tom asso

@SGaist - Yes:

$ echo $LD_LIBRARY_PATH 
/home/oreilly/Qt6.8/Tools/QtCreator/lib:/usr/lib/x86_64-linux-gnu/:/home/oreilly/Qt6.8/6.8.2/gcc_64/lib

SGaist

Why ?

Unset it and try again please.

Tom asso

@SGaist - Oh, it is a mistake to set LD_LIBRARY_PATH when running the installed tools on ubuntu, is that right? I unset LD_LIBRARY_PATH and qtcreator works.
But this presents a problem; the apps I wrote that use Qt6 require LD_LIBRARY_PATH=/home/oreilly/Qt6.8/6.8.2/gcc_64/lib, otherwise they cannot find Qt libraries...

jsulm

@Tom-asso said in qtcreator won't run after update to 6.8.2: xcb error:

But this presents a problem; the apps I wrote that use Qt6 require LD_LIBRARY_PATH

Then start them using a script where you set LD_LIBRARY_PATH. No need to set it globally.
But actually it should not be needed at all if you compiled that apps using that Qt installation.

JonB

@Tom-asso
As @jsulm says. Do you want to examine why you need to set LD_LIBRARY_PATH, you ought not need to?