Crosscompile app using external library

[Antonio Ortiz]

Hi, I want to crosscompile a Qt app to linux armv8.
The app uses libusb to communicate with a periferic device and I need qmake use the right library version depending on the cpu architecture.
I was reading the qmake Variables and Advanced Usage section for anwser and only found how to crosscompile between linux, mac and windows.
Right now I'm using Ubuntu 16 x86_64, QtCreator 3.5.1 and Qt5.8. I already crosscompile Qt5.8 and libusb with linaro and set QtCreator to use the arm kit.
Thanks in advance.

[koahnig]

@Antonio-Ortiz

You are probably missing something like this in your pro-file:

win32:{
include (../CompileSettings/BoostLib.inc)
}
linux:{
INCLUDEPATH += . \
    "/home/xxxx/Source/boost_1_52_0"
}
linux-*:{
INCLUDEPATH += . \
    "/home/xxxx/Source/boost_1_52_0"
}

You find several specifications for setups in mspecs folder of your specofoc Qt setup
Here an example from windows

c:\Qt\5.6\mingw49_32\mkspecs\linux-arm-gnueabi-g++ 

It shows to the linux-arm-gnueabi-g++, which is a general specs for a cross compiler. For cross compiling your Qt you have used this or a similar. You have to give this name already during your configuration of the cross-compile. The example given above is basically distinguishing between a plain win32, a plain linux and a specific linux-* setup. The specific setup is a cross-compile setup, but I was simply too lazy to type the complete name and used a wildcard for qmake.

As you see I am adding here the include path for the booth libs to the compilation. For you it has to be a specific path for the libraries.

[Antonio Ortiz]

Sorry for the late reply.
I was trying with these lines on the pro, but still QtCreator load the x86_64 version of the library

unix
{
    armv8l
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    armeabi-v8l
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    armveabi-v7a
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    gnueabihf
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    gnueabihf-v8l
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    beagle
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    armhf
    {
        LIBS += -L$$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
        INCLUDEPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
        DEPENDPATH += $$PWD/../../../../../Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    }
    x86_64
    {
        LIBS += -L"/usr/local/lib" -lusb-1.0
        INCLUDEPATH += /usr/include/libusb-1.0
        DEPENDPATH += /usr/include/libusb-1.0
    }

}

[Antonio Ortiz]

Thans to your advice @koahnig I could find the solution. I write the g++ version I want to use in the .pro file and QtCreator star loading the right library's version. I put here the final .pro file

linux-beagleboard-g++:{
    LIBS += -L /home/antonio/Aplicaciones/crosscompile/sysroot/usr/opt/libusb/lib/ -lusb-1.0
    INCLUDEPATH += /home/antonio/Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
    DEPENDPATH += /home/antonio/Aplicaciones/crosscompile/sysroot/usr/opt/libusb/include
}
unix:{
    LIBS += -L"/usr/local/lib" -lusb-1.0
    INCLUDEPATH += /usr/include/libusb-1.0
    DEPENDPATH += /usr/include/libusb-1.0
}

[koahnig]

@Antonio-Ortiz

I am glad to see that you could solve your problem.

The wildcard option is quite helpful, but also quite dangerous, if you are not very careful.