I'm attempting to build Mumble on my Windows 10 PC in Qt, and I'm running into some issues (I think I'm just a bit lost on some of the Qt, CMake, and build lingo). I've installed all of the required Qt packages through VCPKG, and I've built the program with almost no issues through the "x64 Native Tools Command Prompt for VS 2019"...
Here is the build documentation that Mumble provides.
I believe what's got me particularly confused is the CMake process. After getting the necessary packages installed, the Mumble instructions have you run the following cmake -G command.
cmake -G "NMake Makefiles" "-DVCPKG_TARGET_TRIPLET=x64-windows-static-md" "-Dstatic=ON" "-DCMAKE_TOOLCHAIN_FILE=D:\Users\Skewb\Documents\repos\vcpkg\scripts\buildsystems\vcpkg.cmake" "-DIce_HOME=D:\Users\Skewb\Documents\repos\vcpkg\installed\x64-windows-static-md" "-DCMAKE_BUILD_TYPE=Release" ..
Followed by the actual "build" command:
cmake --build .
From what I can tell, there's no place for me to input the cmake -G command in the "Build Settings" page. Here's where I've attempted to input it. I've been through the errors below, but I think my lack of understanding of cmake --build and cmake -G has made looking at these files unnecessary.
If I've somehow gotten that correct (I haven't), here's the error I'm getting. It's unable to find the "Ice" directory, but I've specified it in that command.
-- Qt5 component found: Widgets | Version: 5.15.2
CMake Error at cmake/pkg-utils.cmake:87 (message):
Ice component not found: Ice
Call Stack (most recent call first):
src/murmur/CMakeLists.txt:267 (find_pkg)
-- Configuring incomplete, errors occurred!
See also "C:/Users/skewb/AppData/Local/Temp/QtCreator-CfECuA/qtc-cmake-Kjqhpyja/CMakeFiles/CMakeOutput.log".
See also "C:/Users/skewb/AppData/Local/Temp/QtCreator-CfECuA/qtc-cmake-Kjqhpyja/CMakeFiles/CMakeError.log".
CMake process exited with exit code 1.
Elapsed time: 00:55.
I've also gone through these instructions and found the "CMake generator" option in the "Kits" settings, but I don't see anywhere to change the options you feed it:
I think I'm conflating a bunch of terms and their uses in the Mumble documentation vs. Qt including, but not limited to:
Build
Make
Run
Clean
Any help understanding this issue would be greatly appreciated.
I wrote application for linux which uses Qt5.
But when I am trying to launch it on the linux without Qt SDK installed, the output in console is:
Failed to load platform plugin "xcb". Available platforms are:
How can I fix this? May be I need to copy some plugin file?
When I use ubuntu with Qt5 installed, but I rename Qt directory, the same problem occurs. So, it uses some file from Qt directory...
UPDATE:
when I create in the app dir "platforms" folder with the file libqxcb.so, the app still doesnot start, but the error message changes:
Failed to load platform plugin "xcb". Available platforms are:
xcb
How can this happen? How can platform plugin be available but can't be loaded?
Use ldd (man ldd) to show shared library dependencies. Running this on libqxcb.so
.../platforms$ ldd libqxcb.so
shows that xcb depends on libQt5DBus.so.5 in addition to libQt5Core.so.5 and libQt5Gui.so.5 (and many other system libs). Add libQt5DBus.so.5 to your collection of shared libs and you should be ready to move on.
As was posted earlier, you need to make sure you install the platform plugins when you deploy your application. Depending on how you want to deploy things, there are two methods to tell your application where the platform plugins (e.g. platforms/plugins/libqxcb.so) are at runtime which may work for you.
The first is to export the path to the directory through the QT_QPA_PLATFORM_PLUGIN_PATH variable.
QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins ./my_qt_app
or
export QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins
./my_qt_app
The other option, which I prefer is to create a qt.conf file in the same directory as your executable. The contents of which would be:
[Paths]
Plugins=/path/to/plugins
More information regarding this can be found here and at using qt.conf
I tried to start my binary, compiled with Qt 5.7, on Ubuntu 16.04 LTS where Qt 5.5 is preinstalled. It didn't work.
At first, I inspected the binary itself with ldd as was suggested here, and satisfied all "not found" dependencies. Then this notorious This application failed to start because it could not find or load the Qt platform plugin "xcb" error was thrown.
How to resolve this in Linux
Firstly you should create platforms directory where your binary is, because it is the place where Qt looks for XCB library. Copy libqxcb.so there. I wonder why authors of other answers didn't mention this.
Then you may want to run your binary with QT_DEBUG_PLUGINS=1 environment variable set to check which dependencies of libqxcb.so are not satisfied. (You may also use ldd for this as suggested in the accepted answer).
The command output may look like this:
me#xerus:/media/sf_Qt/Package$ LD_LIBRARY_PATH=. QT_DEBUG_PLUGINS=1 ./Binary
QFactoryLoader::QFactoryLoader() checking directory path "/media/sf_Qt/Package/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/media/sf_Qt/Package/platforms/libqxcb.so"
Found metadata in lib /media/sf_Qt/Package/platforms/libqxcb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"xcb"
]
},
"className": "QXcbIntegrationPlugin",
"debug": false,
"version": 329472
}
Got keys from plugin meta data ("xcb")
loaded library "/media/sf_Qt/Package/platforms/libqxcb.so"
QLibraryPrivate::loadPlugin failed on "/media/sf_Qt/Package/platforms/libqxcb.so" : "Cannot load library /media/sf_Qt/Package/platforms/libqxcb.so: (/usr/lib/x86_64-linux-gnu/libQt5DBus.so.5: version `Qt_5' not found (required by ./libQt5XcbQpa.so.5))"
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".
Available platform plugins are: xcb.
Reinstalling the application may fix this problem.
Aborted (core dumped)
Note the failing libQt5DBus.so.5 library. Copy it to your libraries path, in my case it was the same directory where my binary is (hence LD_LIBRARY_PATH=.). Repeat this process until all dependencies are satisfied.
P.S. thanks to the author of this answer for QT_DEBUG_PLUGINS=1.
I tried the main parts of each answer, to no avail. What finally fixed it for me was to export the following environment variables:
LD_LIBRARY_PATH=/usr/local/lib:~/Qt/5.9.1/gcc_64/lib
QT_QPA_PLATFORM_PLUGIN_PATH=~/Qt/5.9.1/gcc_64/plugins/
Ubuntu 16.04 64bit.
I got the problem for apparently no reasons. The night before I watched a movie on my VideoLan instance, that night I would like to watch another one with VideoLan. VLC just didn't want to run because of the error into the question.
I google a bit and I found the solution it solved my problem: from now on, VLC is runnable just like before. The solution is this comand:
sudo ln -sf /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/ /usr/bin/
I am not able to explain what are its consequencies, but I know it creates some missing symbolic link.
Since version 5, Qt uses a platform abstraction system (QPA) to abstract from the underlying platform.
The implementation for each platform is provided by plugins. For X11 it is the XCB plugin. See Qt for X11 requirements for more information about the dependencies.
There might be many causes to this problem. The key is to use
export QT_DEBUG_PLUGINS=1
before you run your Qt application. Then, inspect the output, which will point you to the direction of the error. In my case it was:
Cannot load library /opt/nao/plugins/platforms/libqxcb.so: (/opt/nao/bin/../lib/libz.so.1: version `ZLIB_1.2.9' not found (required by /usr/lib/x86_64-linux-gnu/libpng16.so.16))
But that is solved in different threads. See for instance https://stackoverflow.com/a/50097275/2408964.
Probably this information will help. I was on Ubuntu 18.04 and when I tried to install Krita, using the ppa method, I got this error:
This application failed to start because it could not find or load the Qt platform plugin "xcb" in "".
Available platform plugins are: linuxfb, minimal, minimalegl, offscreen, wayland-egl, wayland, xcb.
Reinstalling the application may fix this problem.
Aborted
I tried all the solutions that I found in this thread and other webs without any success.
Finally, I found a post where the author mention that is possible to activate the debugging tool of qt5 using this simple command:
export QT_DEBUG_PLUGINS=1
After adding this command I run again krita I got the same error, however this time I knew the cause of that error.
libxcb-xinerama.so.0: cannot open shared object file: No such file or directory.
This error prevents to the "xcb" to load properly. So, the solution will be install the `libxcb-xinerama.so.0" right? However, when I run the command:
sudo apt install libxcb-xinerama
The lib was already installed. Now what Teo? Well, then I used an old trick :) Yeah, that one --reinstall
sudo apt install --reinstall libxcb-xinerama
TLDR: This last command solved my problem.
I ran into a very similar problem with the same error message. First, debug some by turning on the Qt Debug printer with the command line command:
export QT_DEBUG_PLUGINS=1
and rerun the application. For me this revealed the following:
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
Indeed, I was missing libxkbcommon-x11.so.0 and libxkbcommon-x11.so.0. Next, check your architecture using dpkg from the linux command line. (For me, the command "arch" gave a different and unhelpful result)
dpkg --print-architecture #result for me: amd64
I then googled "libxkbcommon-x11.so.0 ubuntu 18.04 amd64", and likewise for libxkbcommon-x11.so.0, which yields those packages on packages.ubuntu.com. That told me, in retrospect unsurprisingly, I'm missing packages called libxkbcommon-x11-0 and libxkbcommon0, and that installing those packages will include the needed files, but the dev versions will not. Then the solution:
sudo apt-get update
sudo apt-get install libxkbcommon0
sudo apt-get install libxkbcommon-x11-0
So, I spent about a day trying to figure out what was the issue; tried all the proposed solutions, but none of that worked like installing xcb libs or exporting Qt plugins folder. The solution that suggested to use QT_DEBUG_PLUGINS=1 to debug the issue didn't provide me a direct insight like in the answer - instead I was getting something about unresolved symbols within Qt5Core.
That gave me a hint, though: what if it's trying to use different files from different Qt installations? On my machine I had standard version installed in /home/username/Qt/ and some local builds within my project that I compiled by myself (I have other custom built kits as well in other locations). Whenever I tried to use any of the kits (installed by Qt maintenance tool or built by myself), I would get an "xcb error".
The solution was simple: provide the Qt path through CMAKE_PREFIX_PATH and not though Qt5_DIR as I did, and it solved the problem. Example:
cmake .. -DCMAKE_PREFIX_PATH=/home/username/Qt/5.11.1/gcc_64
I faced the same problem when after installing Viber. It had all required qt libraries in /opt/viber/plugins/.
I checked dependencies of /opt/viber/plugins/platforms/libqxcb.so and found missing dependencies. They were libxcb-render.so.0, libxcb-image.so.0, libxcb-icccm.so.4, libxcb-xkb.so.1
So I resolved my issue by installing missing packages with this libraries:
apt-get install libxcb-xkb1 libxcb-icccm4 libxcb-image0 libxcb-render-util0
I like the solution with qt.conf.
Put qt.conf near to the executable with next lines:
[Paths]
Prefix = /path/to/qtbase
And it works like a charm :^)
For a working example:
[Paths]
Prefix = /home/user/SDKS/Qt/5.6.2/5.6/gcc_64/
The documentation on this is here: https://doc.qt.io/qt-5/qt-conf.html
All you need to do is
pip uninstall PyQt5
and
conda install pyqt
Most of the problem of pyqt can be fixed by this simplest solution.
In my case, I needed to deploy two Qt apps on an Ubuntu virtualbox guest. One was command-line ("app"), the other GUI_based ("app_GUI").
I used "ldd app" to find out what the required libs are, and copied them
to the Ubuntu guest.
While the command-line executable "app" worked ok, the GUI-based executable crashed, giving
the "Failed to load platform plugin "xcb" error. I checked ldd for libxcb.so, but this too had no missing dependencies.
The problem seemed to be that while I did copy all the right libraries I accidentally had copied also libraries that were already present at the guest system.. meaning that (a) they were unnecessary to copy them in the first place and (b) worse, copying them produced incompatibilities between the install libraries.
Worse still, they were undetectable by ldd like I said..
The solution? Make sure that you copy libraries shown as missing by ldd and absolutely no extra libraries.
In my case missing header files were the reason libxcb was not built by Qt. Installing them according to https://wiki.qt.io/Building_Qt_5_from_Git#Linux.2FX11 resolved the issue:
yum install libxcb libxcb-devel xcb-util xcb-util-devel mesa-libGL-devel libxkbcommon-devel
Folks trying to get this started on Ubuntu 20.04 please try to run this and see if this solves the problem. This worked for me
sudo apt-get update -y
sudo apt-get install -y libxcb-xinerama0
I link all Qt stuff statically to the generic Linux builds of my open source projects. It makes life a bit easier. You just need to build static versions of Qt libraries first. Of course this cannot be applied to closed source software due to licensing issues. The deployment of Qt5 apps on Linux is currently a bit problematic, because Ubuntu 12.04, for example, doesn't have Qt5 libraries in the package repositories.
I had this problem, and on a hunch I removed the Qt Configs from my environment. I.e.,
rm -rf ~/.config/Qt*
Then I started qtcreator and it reconfigured itself with the existing state of the machine. It no longer remembered where my projects were, but that just meant I had to browse to them "for the first time" again.
But more importantly it built itself a coherent set of library paths, so I could rebuild and run my project executables again without the xcb or qxcb libraries going missing.
I faced the same situation, but on a Ubuntu 20.04 VM.
TL;DR: Check file permissions.
What I did:
I copied the Qt libs required to /usr/local/lib/x86_64-linux-gnu/ and added it to LD_LIBRARY_PATH
I copied the platforms folder from Qt to my application directory and added it to QT_PLUGIN_PATH
I ran ldd on the executable and in the offending libqxcb.so (ldd libqxcb.so), and it complains about some dependencies although ldconfig listed them as found.
linux-vdso.so.1 (0x00007ffee19af000)
libQt5XcbQpa.so.5 => not found
libfontconfig.so.1 => /lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f7cb18fb000)
libfreetype.so.6 => /lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f7cb183c000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f7cb1820000)
libQt5Gui.so.5 => /usr/local/lib/x86_64-linux-gnu/libQt5Gui.so.5 (0x00007f7cb0fd4000)
libQt5DBus.so.5 => not found
I used export QT_DEBUG_PLUGINS=1 for further info. It complains about missing files, although they are there.
What I found:
For some reason, when copying to the VM through the shared folder the files permissions were not the correct ones.
Thus, I ran: sudo chmod 775 * on the libs and voilà.
I solved the issue through this https://github.com/NVlabs/instant-ngp/discussions/300
pip uninstall opencv-python
pip install opencv-python-headless
This seems to have been a problem with the cv2 Python package and how it loops in Qt
sudo ln -sf /usr/lib/...."adapt-it"..../qt5/plugins/platforms/ /usr/bin/
It creates the symbolic link it's missed. Good for QT ! Good for VLC !!
Due to concerns with some Qt libraries with GPL licenses(most are LGPL available), we removed most unused dependencies on our project. After running windeployqt:
windeployqt.exe --dir setup --compiler-runtime --release --qmldir ..\Qml ..\release\OUREXE.exe
We get following logs:
Direct dependencies: Qt5Core Qt5Gui Qt5Network Qt5Qml Qt5Quick Qt5WebSockets Qt5Widgets Qt5WebEngineCore Qt5WebEngineWidgets Qt53DCore Qt53DRender Qt53DInput Qt53DExtras
All dependencies : Qt5Concurrent Qt5Core Qt5Gamepad Qt5Gui Qt5Network Qt5Positioning Qt5PrintSupport Qt5Qml Qt5Quick Qt5QuickWidgets Qt5WebSockets Qt5Widgets Qt5WinExtras Qt5WebEngineCore Qt5WebEngineWidgets Qt53DCore Qt53DRender Qt53DQuick Qt53DQuickRender Qt53DInput Qt53DAnimation Qt53DExtras Qt5WebChannel
To be deployed : Qt5Concurrent Qt5Core Qt5Gamepad Qt5Gui Qt5Network Qt5Positioning Qt5PrintSupport Qt5Qml Qt5Quick Qt5QuickWidgets Qt5SerialPort Qt5Svg Qt5WebSockets Qt5Widgets Qt5WinExtras Qt5WebEngineCore Qt5WebEngineWidgets Qt53DCore Qt53DRender Qt53DQuick Qt53DQuickRender Qt53DInput Qt53DAnimation Qt53DExtras Qt5WebChannel
As you can see, despite windeployqt being aware of "needed" modules, it seems to deploy all Qt modules, even unused ones.
I am aware it is possible to use "--no-" option to manually exclude modules, but I want windeployqt to automatically detect and add only direct dependencies. Is there a way to limit deployed modules to bare minimum with this program?
Turns out Qt53DQuick is NOT QtQuick 3D module library. Qt 5.12.x does not have QtQuick 3D module, and the dlls are part of the Qt3D module.
I'm trying to build our application using Qt 5.13.0 installed via Conan/Artifactory. We run our own Artifactory server and the Qt version there is self-build (and statically linked) in our CI solution. We use the Conan recipe for Qt written by the bincrafters, slightly modified to apply some patches for known Qt bugs and set some flags for building properly on Android and WebAssembly.
When trying to build the application, the linker fails to find the necessary dependencies for Qt itself because it tries to look them up in the home folder of the user who build the Qt package, not the user who's running the build.
Here's an excerpt from the build log, showing the attempt at linking all previously compiled object files together:
application folder-------v subproject of the application----v-------v dependency of the application, correct user home dir---------v Qt library installed via Conan, correct user home dir-------v dependency of Qt, WRONG user home dir------------v
g++ -Wl,--gc-sections -o ../../fah [--> all the .o files <--] -L../lib -lmodel -lcore [--> more linked libraries and application parts <--] -L/home/kaupes/.conan/data/libsodium/1.0.18/bje/stable/package/d1efe3774eed76670888f919621e7c4e1b52efa9/lib /home/kaupes/.conan/data/qt/5.13.0/bje/stable/package/d6b3f512e1a5607061462f94e3271dc8af3dd516/lib/libQt5Gui.a /home/dev/.conan/data/harfbuzz/2.4.0/bje/stable/package/c68551ae35bf5d62e66263379d58a38416eb84a9/lib/libharfbuzz.a [--> many, many more libraries <--]
g++: error: /home/dev/.conan/data/harfbuzz/2.4.0/bje/stable/package/c68551ae35bf5d62e66263379d58a38416eb84a9/lib/libharfbuzz.a: No such file or directory
many, many more errors...
As you can see, the user running the build is kaupes, but the g++ invocation attempts to look for the dependencies in /home/dev/, the home folder of the CI user who build the Qt Conan package.
Only dependencies of Qt itself have the problem. Dependencies of the application (also installed via Conan) are found at the correct place.
The Qt package has been build in the CI using the following Conan invocation:
conan create --profile .conan/profiles/linux -s compiler=gcc -s compiler.version=9 . fah/stable
Compiler and version are explicitly set because I'm also build for another GCC version. The linux profile file also doesn't do anything interesting (as far as I can see):
include(default)
[settings]
build_type=Release
compiler.libcxx=libstdc++11
[options]
OpenSSL:shared=False
OpenSSL:no_asm=True
OpenSSL:no_asm=True
OpenSSL:no_weak_ssl_ciphers=True
OpenSSL:no_ssl2=True
OpenSSL:no_ssl3=True
OpenSSL:no_engine=True
libcurl:shared=False
libxml2:shared=False
libxml2:fPIC=True
libsodium:shared=False
pcre2:shared=False
libpng:shared=False
freetype:shared=False
bzip2:shared=False
libjpeg:shared=False
harfbuzz:shared=False
xkbcommon:shared=False
qt:shared=False
qt:with_glib=False
qt:with_sqlite3=False
qt:with_mysql=False
qt:with_pq=False
qt:with_odbc=False
qt:with_sdl2=False
qt:with_openal=False
qt:with_libalsa=False
qt:openssl=True
qt:commercial=False
qt:qtsvg=True
qt:qtdeclarative=True
qt:qtactiveqt=False
qt:qtscript=False
qt:qtmultimedia=False
qt:qttools=True
qt:qtxmlpatterns=False
qt:qttranslations=True
qt:qtdoc=False
qt:qtrepotools=False
qt:qtqa=False
qt:qtlocation=True
qt:qtsensors=True
qt:qtwayland=True
qt:qt3d=False
qt:qtimageformats=False
qt:qtgraphicaleffects=True
qt:qtquickcontrols=True
qt:qtserialbus=False
qt:qtserialport=False
qt:qtx11extras=True
qt:qtmacextras=False
qt:qtwinextras=False
qt:qtandroidextras=False
qt:qtwebsockets=True
qt:qtwebchannel=False
qt:qtwebengine=False
qt:qtwebview=False
qt:qtquickcontrols2=True
qt:qtpurchasing=False
qt:qtcharts=True
qt:qtdatavis3d=False
qt:qtvirtualkeyboard=True
qt:qtgamepad=False
qt:qtscxml=False
qt:qtspeech=False
qt:qtnetworkauth=False
qt:qtremoteobjects=False
qt:qtwebglplugin=False
qt:qtlottie=False
qt:qtconnectivity=True
Is there something I'm doing wrong during the Conan package creation or installation or is this caused by something different?
Indeed, when building qt, all paths to dependencies are hardcoded in configurations files (mkspecs\modules\qt_lib_*.pri).
I assume you are building your application with qmake, because you use static qt, and static qt is incompatible with cmake. One thing you could try is to pass the full path to harfbuzz lib to qmake by adding argument QMAKE_LIBS_HARFBUZZ=/home/kaupes/.conan/data/harfbuzz/2.4.0/bje/stable/package/c68551ae35bf5d62e66263379d58a38416eb84a9/lib/libharfbuzz.a to your qmake invocation.
Edit: it seems to be a knwonw behaviour of qt >= 5.12.1 : https://bugreports.qt.io/browse/QTBUG-72903. This feature has been reverted in 5.14.x and 5.15.x with https://github.com/qt/qtbase/commit/9864d2c6f3b628ca9f07a56b197e77bd43931cca
I've downloaded and installed the QT SDK and downloaded the QT Mobility source.
Following the provided instructions, I navigated to my QtMobility directory via the Visual Studio Command Prompt (2010)... note, this is the QtMobility dir with the bin, plugins, examples, etc. folders.
D:\
cd D:\Files\Downloads\QtMobility
configure
Regardless of whether I gave configure a -prefix parameter or not, the following output was displayed:
Checking available Qt
4.8.2
Checking make
... Unknown target environment .
Cannot find 'nmake', 'mingw32-make' or 'make' in your PATH
Aborting.
Of course, I then went to see if my computer had nmake in its PATH: the directory is added as follows:
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin
I went to CMD and typed in "nmake /?" to receive proper output.
What am I doing wrong? When I try to simply run nmake in the QTMobility directory, it displays:
NMAKE : fatal error U1064: MAKEFILE not found and no target specified
Stop.
Help, please! Thank you. :) I will continue attempting debugs on my own...
I suppose this is late but you could simply run the visual studio command prompt, as it has specific env. variables preset to find nmake, etc.