与CMake交叉编译：如何排除默认的qt库，而不是将它们传递给链接器的命令行

Question

I want to cross-compile Qt planets demo applicatioin on Linux x64 with CMake for ARM.

I installed arm cross compiler. I've built Qt libs on ARM board and copied them to x64 Linux box's /lib/arm-linux-gnueabihf.

For qmake I did this with only adding few lines to planets.pro file:

PLATFORM = arm-linux-gnueabihf
QMAKE_CXX = /usr/bin/$$PLATFORM-g++
QMAKE_LINK = /usr/bin/$$PLATFORM-g++
QMAKE_LIBS = -L/usr/$$PLATFORM/lib -L/lib/$$PLATFORM

It compiles successfully and runs perfectly on ARM board.

Now, I want to do this with CMake. So, I created the following CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

set(PLATFORM arm-linux-gnueabihf)
set(CMAKE_CXX_COMPILER /usr/bin/${PLATFORM}-g++)
link_directories(/usr/${PLATFORM}/lib /lib/${PLATFORM})

file(GLOB_RECURSE HEADERS "*.hpp")
file(GLOB SOURCES "*.cpp")

set(CMAKE_AUTOMOC ON)

find_package(Qt5Qml REQUIRED)
find_package(Qt5Quick REQUIRED)

add_executable(planets-qml ${SOURCES})

target_link_libraries(planets-qml
    Qt5::Qml
    Qt5::Quick
)

With this I have the following warning in Qt Creator's log:

Cannot generate a safe runtime search path for target planets-qml because
files in some directories may conflict with libraries in implicit
directories:

runtime library [libGL.so.1] in /usr/lib/x86_64-linux-gnu may be hidden by files in:
  /lib/arm-linux-gnueabihf

Then, I'm building it, and I got linker error:

/home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Quick.so.5.7.0: 
file not recognized: File format not recognized

I assume this happens because linker tries to link x64 Qt libraries to ARM binary. But why can't it find libs from /lib/arm-linux-gnueabihf ?

I found the command to the linker in the file linker.txt:

/usr/bin/arm-linux-gnueabihf-g++ 
    CMakeFiles/planets-qml.dir/main.cpp.o 
    CMakeFiles/planets-qml.dir/planets-qml_automoc.cpp.o  
    -o planets-qml  
    -L/usr/arm-linux-gnueabihf/lib  -L/lib/arm-linux-gnueabihf 
    /home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Quick.so.5.7.0 
    /home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Qml.so.5.7.0 
    /home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Network.so.5.7.0 
    /home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5.7.0 
    /home/dev/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5.7.0 
    -Wl,-rpath,/usr/arm-linux-gnueabihf/lib:/lib/arm-linux-gnueabihf:/home/dev/Qt5.7.0/5.7/gcc_64/lib 

So, the question is: How to exclude these /home/dev/Qt5... entries and not to pass them to the linker? What CMake command should I use in CMakeLists.txt file?

Answer 1

Problem is that you are looking at the wrong QT directory. You need to recompile Qt for ARM. Then set Qt5_DIR before find_package calls.

set(Qt5_DIR  <path-to-Qt>/lib/cmake/Qt5/)

Your <path-to-Qt>/lib/cmake/Qt5/ should look like this:

$ ls <path-to-Qt>/lib/cmake/Qt5/
Qt5Config.cmake        Qt5ConfigVersion.cmake