Statically linked app with Qt gives error: Failed to load platform plugin "windows"

Question

I have built Qt 5.0.1 statically in VS 2010 under Windows 7 x64. The configuration parameters were

configure -debug-and-release -opensource -confirm-license -platform win32-msvc2010 -nomake examples -nomake tests -no-webkit -static

and I performed the build with jom with following parameters:

jom -j 4

The build process was successful and I can find all the libs and link my app with Qt statically. Now the problem is that when I try to run the application, it gives me an error

Module: 5.0.1
File: kernel\qguiapplication.cpp
Line: 781
"Failed to load platform plugin "windows". Available platforms are:"

But below this error, it does not show up any platforms. I encountered the same error while linking with Qt dynamically. I got rid of that by placing dependency DLLs (qt5core.dll, qt5gui.dll etc) in the same directory of my exe. But I can't figure out a way this time.

After static build of Qt, the DLLs in the plugins/platforms/ folder are gone and they are replaced by libs. I have also tried to statically link with qwindows.lib but to no avail.

Any idea? Regards.

Answer 1

To check what DLL are needed to deploy your application on Windows, use dependency Walker (http://www.dependencywalker.com/).

According to the documentation page Qt for Windows - Deployment some DLL are required to deploy a Qt application on Windows platforms:

• qwindows.dll
• icudtXX.dll
• icuinXX.dll
• icuucXX.dll
• libGLESv2.dll
• libEGL.dll

Depending on the compiler you use to compile the application, some other libraries may be required:

• MSVC specific libraries:
  • msvcrXX.dll
  • msvcpXX.dll
• MinGW specific libraries
  • libgcc_s_dw2-1.DLL
  • libstdc++-6.dll

Note: in all these files, replace XX by the current version of the DLL on your system.

If you didn't build Qt statically (default), you will also need Qt5 DLL depending on Qt module you use in your application. Example:

• Qt5Core.dll
• Qt5Test.dll
• Qt5Network.dll
• etc.

All these DLL can be found in "bin" folder, under your Qt installation dir.

EDIT

Recently, Qt developers created a tool named windeployqt.exe which helps you to gather all required library to deploy an application:

Usage: windeployqt [options] [file]
Qt Deploy Tool 5.3.0

The simplest way to use windeployqt is to add the bin directory of your Qt
installation (e.g. <QT_DIR\bin>) to the PATH variable and then run:
  windeployqt <path-to-app-binary>
If ICU, ANGLE, etc. are not in the bin directory, they need to be in the PATH
variable. If your application uses Qt Quick, run:
  windeployqt --qmldir <path-to-app-qml-files> <path-to-app-binary>

Options:
  -?, -h, --help            Displays this help.
  -v, --version             Displays version information.
  --dir <directory>         Use directory instead of binary directory.
  --libdir <path>           Copy libraries to path.
  --debug                   Assume debug binaries.
  --release                 Assume release binaries.
  --force                   Force updating files.
  --dry-run                 Simulation mode. Behave normally, but do not
                            copy/update any files.
  --no-plugins              Skip plugin deployment.
  --no-libraries            Skip library deployment.
  --qmldir <directory>      Scan for QML-imports starting from directory.
  --no-quick-import         Skip deployment of Qt Quick imports.
  --no-translations         Skip deployment of translations.
  --no-system-d3d-compiler  Skip deployment of the system D3D compiler.
  --compiler-runtime        Deploy compiler runtime (Desktop only).
  --no-compiler-runtime     Do not deploy compiler runtime (Desktop only).
  --webkit2                 Deployment of WebKit2 (web process).
  --no-webkit2              Skip deployment of WebKit2.
  --json                    Print to stdout in JSON format.
  --list <option>           Print only the names of the files copied.
                            Available options:
                             source:   absolute path of the source files
                             target:   absolute path of the target files
                             relative: paths of the target files, relative
                                       to the target directory
                             mapping:  outputs the source and the relative
                                       target, suitable for use within an
                                       Appx mapping file
  --verbose <level>         Verbose level.

Qt libraries can be added by passing their name (-xml) or removed by passing
the name prepended by --no- (--no-xml). Available libraries:
bluetooth clucene concurrent core declarative designercomponents designer gui
clucene qthelp multimedia multimediawidgets multimediaquick network nfc opengl
positioning printsupport qml quick quickparticles script scripttools sensors
serialport sql svg test widgets winextras xml xmlpatterns

Arguments:
  [file]                    Binary or directory containing the binary.

Answer 2

I just had the same problem, so here is my solution:

First of course build QT with the -static parameter.

Add the following libs to your build:

Qt5PlatformSupport.lib
qwindows.lib
imm32.lib

Add the following path to your library paths:

$(QTDIR)\plugins\platforms

In your code (preferably main.cpp) add the following line:

Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)

The resulting build should not depend on any qt-related dlls.