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