Qt6 on Linux for Windows如何交叉编译？

Question

I'm trying to cross-compile Qt 6.2.1. Target - Windows, my machine OS - Linux (Mint 20.2) (both 64bit). Unfortunately I can't compile it on Windows, so I have to do this cross-compilation.

My configure cmd:

./../qt-everywhere-src-6.2.1/configure -prefix $PWD/. -platform linux-gcc-64 -xplatform win32-g++ -device-option CROSS_COMPILE=/usr/bin/x86_64-w64-mingw32- -opensource -opengl desktop -qt-host-path /home/papoj/Projects/host_qtbuild

At the end of CMake work I'm getting this:

CMake Warning:
  Manually-specified variables were not used by the project:

    QT_QMAKE_DEVICE_OPTIONS

And then, after cmake --build. --parallel:

FAILED: qtbase/src/tools/bootstrap/CMakeFiles/Bootstrap.dir/__/__/corelib/global/qglobal.cpp.o 
/usr/bin/c++ -DHAVE_CONFIG_H -DQT_BOOTSTRAPPED -DQT_NO_CAST_FROM_ASCII -DQT_NO_CAST_TO_ASCII -DQT_NO_DEBUG -DQT_NO_FOREACH -DQT_USE_QSTRINGBUILDER -DQT_VERSION_MAJOR=6 -DQT_VERSION_MINOR=2 -DQT_VERSION_PATCH=1 -DQT_VERSION_STR=\"6.2.1\" -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -I/home/papoj/Projects/qtbuild/qtbase/src/corelib/Core_autogen/include -I/home/papoj/Projects/qtbuild/qtbase/include -I/home/papoj/Projects/qtbuild/qtbase/include/QtCore -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib -I/home/papoj/Projects/qtbuild/qtbase/src/corelib -I/home/papoj/Projects/qtbuild/qtbase/src/corelib/global -I/home/papoj/Projects/qtbuild/qtbase/src/corelib/kernel -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/../3rdparty/tinycbor/src -I/home/papoj/Projects/qtbuild/qtbase/include/QtCore/6.2.1 -I/home/papoj/Projects/qtbuild/qtbase/include/QtCore/6.2.1/QtCore -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/../3rdparty/double-conversion/double-conversion -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/../3rdparty/double-conversion -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/../3rdparty/forkfd -I/home/papoj/Projects/qtbuild/qtbase/src/corelib/.rcc -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/mkspecs/win32-g++ -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/home/papoj/Projects/qtbuild/qtbase/src/xml/Xml_autogen/include -I/home/papoj/Projects/qtbuild/qtbase/include/QtXml -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/xml -I/home/papoj/Projects/qtbuild/qtbase/src/xml -I/home/papoj/Projects/qtbuild/qtbase/include/QtXml/6.2.1 -I/home/papoj/Projects/qtbuild/qtbase/include/QtXml/6.2.1/QtXml -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/tools/bootstrap/.. -I/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/tools/bootstrap/../../3rdparty/tinycbor/src -DNDEBUG -O2 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -Wall -Wextra -ffunction-sections -fdata-sections -mshstk -Wsuggest-override -std=gnu++17 -MD -MT qtbase/src/tools/bootstrap/CMakeFiles/Bootstrap.dir/__/__/corelib/global/qglobal.cpp.o -MF qtbase/src/tools/bootstrap/CMakeFiles/Bootstrap.dir/__/__/corelib/global/qglobal.cpp.o.d -o qtbase/src/tools/bootstrap/CMakeFiles/Bootstrap.dir/__/__/corelib/global/qglobal.cpp.o -c /home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/global/qglobal.cpp
In file included from /home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/src/corelib/global/qglobal.cpp:41:
/home/papoj/Projects/qt-everywhere-src-6.2.1/qtbase/mkspecs/win32-g++/qplatformdefs.h:55:10: fatal error: tchar.h: No such file or directory
   55 | #include <tchar.h>
      |          ^~~~~~~~~

I have checked (this is also visible in log above) and CMake, for some reason, ignore my "CROSS_COMPILE" option and uses Linux c++ tool to compile instead of 'x86_64-w64-mingw32-g++', but I dont know how to fix that.

Does anybody cross-compiled Qt6 for Windows on Linux manually? I cannot find any working solution on the Inte.net.

Answer 1

For those coming here from google with same problem.

In Qt6 you need to specify Cmake toolchain for cross-compilation (I get something similar to toolchain shared here ), as 'alone' device-option CROSS_COMPILE (as in cmd from my question) is depreciated/outdated (or smth like that).

In my case I needed to use CMake toolchain and device-option CROSS-COMPILE as well, because in other way qmake was not able to find proper cross-platform compiler (in my case x86_64-w64-mingw32-g++-posix). To use compiler with "posix" at the end I needed to modify qtbase/mkspecs/win32-g++/qmake.conf. This is how it looks like after changes:

#
# qmake configuration for win32-g++
#
# Written for MinGW-w64 / gcc 5.3 or higher
#
# Cross compile example for i686-w64-mingw32-g++:
#   configure -xplatform win32-g++ -device-option CROSS_COMPILE=i686-w64-mingw32-
#

include(../common/g++-win32.conf)
include(../common/windows-desktop.conf)

# modifications to g++-win32.conf

QMAKE_CC                = $${CROSS_COMPILE}gcc-posix
QMAKE_CFLAGS           += -fno-keep-inline-dllexport
QMAKE_CFLAGS_WARN_ON   += -Wextra

QMAKE_CXX               = $${CROSS_COMPILE}g++-posix
QMAKE_CXXFLAGS         += -fno-keep-inline-dllexport
QMAKE_CXXFLAGS_WARN_ON  = $$QMAKE_CFLAGS_WARN_ON
QMAKE_CXXFLAGS_EXCEPTIONS_ON += -mthreads

QMAKE_LINK              = $${CROSS_COMPILE}g++-posix
QMAKE_LINK_C            = $${CROSS_COMPILE}gcc-posix

QMAKE_CFLAGS_LTCG       = -flto
QMAKE_CXXFLAGS_LTCG     = $$QMAKE_CFLAGS_LTCG
QMAKE_LFLAGS_LTCG       = $$QMAKE_CFLAGS_LTCG
QMAKE_LFLAGS_EXCEPTIONS_ON += -mthreads

load(qt_config)

Final./configure cmd:

./../qt-everywhere-src-6.2.1/configure -prefix $HOME/Projects/testing_qt_builds/qtbuild_with_old_params -platform linux-g++ -xplatform win32-g++ -device-option CROSS_COMPILE=/usr/bin/x86_64-w64-mingw32- -opensource -opengl desktop -qt-host-path $HOME/Qt/6.2.1/gcc_64 -nomake tests -nomake examples -skip qtwebengine -- -DQT_BUILD_TOOLS_WHEN_CROSSCOMPILING=ON -DCMAKE_TOOLCHAIN_FILE=$HOME/Projects/toolchain.cmake

After cmake --build and cmake --install I got host-qmake script in my build path

$HOME/Projects/testing_qt_builds/qtbuild_with_old_params/bin/

Which I had to use to build my Qt project by passing.pro file to it. And then I just copied.exe file to Windows, provided all needed dlls and POOF, app works. :D

My thread on qt forum with same problem where one of moderators helped me a lot to get final solution.

Answer 2

Another, possibly simpler approach to cross-compiling Qt for Windows on Linux is to use qmake with MXE and mxedeployqt (the latter is the equivalent of windeployqt and collates the required DLLs).

I've got a couple of projects that use MXE and mxedeployqt within Docker to build Qt. The docker container builds MXE from source (because I wanted a recent gcc and it wasn't available in the MXE repositories) which takes a long time, but once that's done, compiling Qt code is very straightforward: docker-compose up .

Once set up, creating a new project that uses the same method is very simple as it uses the same Dockerfile and build script. Two example repositories that use this method are ARPCalc and Digraph . Most of the configuration required to get a working build system is in the dockerfiles/winqt folder: https://github.com/abudden/digraph/blob/master/dockerfiles/winqt