How do I setup a kit to crosscompile for Raspbian for the Pi3?



  • I'm used to using Qt for the desktop, but for the life of me I can't find any instructions for setting up my Linux box Qt5.11 to compile for Raspbian. All the instructions I've come across want to force the pi to boot to Qt. I don't want to do that. I just want to make an app and run it on the pi. How do I do this?



  • a litte bit outdated but you´ll get the idea

    https://wiki.qt.io/RaspberryPi2EGLFS





  • @sneubert The very first sentence explains that this is to do exactly what I DON'T want to do. I DON'T want to make an embedded full screen app. I WANT to make a widget app for the Pi.



  • @sneubert It would be doubly awesome if I could cross compile the thing to save development time.


  • Lifetime Qt Champion

    Hi,

    Then use the xcb backend on the Pi like it's used on the desktop.



  • @graniteDev

    to add to SGaist, the mentionted guide is not using Qt for Device Creation (boot to Qt).
    Your are right the guide states it´s not intended for running desktop-style, windowed Qt apps under X11 but as it´s an howto on setting up a crosscompiler for raspbian your are free to choose the platform plugin used to display your app. For XCB see http://doc.qt.io/qt-5/embedded-linux.html#xcb
    Maybe you have to add some additional libs to be able to compile xcb (http://doc.qt.io/qt-5/linux-requirements.html).
    But once again, even if you use the eglfs plugin it´s not using boot to Qt! You are only not using a window manager. BTW this is independent from the decision using widgets or quick, if you use vc4 on the rpi



  • @sneubert
    Alright, I'll have to try to figure this out. I'm not familiar enough with Qts inner workings as on the desktop, you download Qt Creator, chose your version of Qt, and then your set.



  • I've not been able to get passed this part of the instructions from this link https://wiki.qt.io/RaspberryPi2EGLFS

    git clone git://code.qt.io/qt/qtbase.git -b <qt-version>
    cd qtbase
    ./configure -release -opengl es2 -device <rpi-version> -device-option CROSS_COMPILE=~/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf- -sysroot ~/raspi/sysroot -opensource -confirm-license -make libs -prefix /usr/local/qt5pi -extprefix ~/raspi/qt5pi -hostprefix ~/raspi/qt5 -v
    

    And I modified it to be as so to fit my configuration and run it inside the raspi/qtbase/ directory

    ./configure -release -opengl es2 -device linux-rasp-pi3-g++ -device-option CROSS_COMPILE=/home/brandon/development/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf- -sysroot /home/brandon/development/raspi/sysroot -opensource -confirm-license -make libs -prefix /usr/local/qt5pi -extprefix /home/brandon/development/raspi/qt5pi -hostprefix /home/brandon/development/raspi/qt5 -v
    

    It runs for a while, lots of text flying passed the screen, and then it stops, and says it this:

    Project ERROR: Cannot run target compiler '/home/brandon/development/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-g++'. Output:
    ===================
    sh: 1: /home/brandon/development/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-g++: not found
    ===================
    Maybe you forgot to setup the environment?
    
    

    I don't have the compiler, but I don't know why it's missing. I have not had any issues with the instructions up to this point - but since I'm completely baffled by what exactly the instructions are having me do, I don't know how fix this.

    For the record, it's completely maddening how difficult it is to get setup to build for the pi. I don't understand why this is so difficult when Qt makes so easy on everything else.


  • Qt Champions 2017

    @graniteDev said in How do I setup a kit to crosscompile for Raspbian for the Pi3?:

    I don't have the compiler, but I don't know why it's missing.

    Huh? Either you have it, or not. In your configure line, you told configure to use the toolchain CROSS_COMPILE=~/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-.

    Did you mean .../usr/bin/arm-linux-gnueabihf- ?

    Or where is your cross-toolchain installed?



  • This post is deleted!

  • Qt Champions 2017

    @graniteDev

    You still didn't answer my question:

    Or where is your cross-toolchain installed?

    In other words, where is arm-linux-gnueabihf-g++ located?

    So I honestly don't know if that's right or wrong because i'm not at all familiar with this process.

    If you like it or not, cross-compiling is an advanced topic which requires deep understanding of the involved tools.

    You should probably start cross-compiling a "hello world" application before trying a large library like Qt.



  • So i search for the compiler after digging into the details and the error appears to be in error. That entire path that it says doesn't exist, does exist.

    /home/brandon/development/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-g++

    I can cd into that last bin directory and there are about 2 dozen compilers in there and arm-linux-gnueabihf-g++ is in there. for some reason it appends g++ to the string which is why the instructions have you only put " arm-linux-gnueabihf-"

    So now I understand better what it wants, but not why it can't find it.


  • Qt Champions 2017

    @graniteDev

    Ok, so the paths are 100% the same? Does the compiler arm-linux-gnueabihf-g++ have the executable bit set? Sometimes you also have to call an "enviroment-setup" script to use the cross toolchain, not sure if that applies to your toolchain also.

    Btw: arm-linux-gnueabihf- is the cross-toolchain-prefix, which tells you that the compiler produces "arm" executables for linux. "hf" stands for hardware floating point support and "gnueabi", I honestly would have to google it ;) g++ is just the GNU GCC C++ compiler. Your normal compiler is therefore called g++, and the cross-compiler is called arm-linux-gnueabihf-g++.



  • @aha_1980

    Double checked, yes it has the execution bit set for own, group and everyone else. I've added that bin to the path for good measure.

    Here is something odd. If I cd into that bin directory and

    ./arm-linux-gnueabihf-g++
    

    the result

    bash: ./arm-linux-gnueabihf-g++: No such file or directory
    

    What seriously is wrong? The file is right in that directory! It even autocompletes for me! I really don't get this.


  • Qt Champions 2017

    @graniteDev

    Puh, that's getting a tough one. But I don't give up yet. Can you please do a file ./arm-linux-gnueabihf-g++ in that directory and post the output here?



  • @aha_1980

    No problem:

    ./arm-linux-gnueabihf-g++: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 2.6.15, stripped
    

    ok....is it a problem that that says intel and I'm running amd?


  • Qt Champions 2017

    @graniteDev

    Ok, I think you your problem is, that this toolchain is for 32-Bit PC (i.e. x86), while you are probably running a 64 bit system (i.e. x86_64, you can check with the arch command).

    It might be possible to get this to run, but I'd rather recommend you to get a toolchain that directly runs on your system. you avoid the memory limits of 32 bit architecture with that also.

    So far...



  • @aha_1980 Hmm...ok, maybe I missunderstood some of the instruction when it talked about 64bit. I assumed it was talking about the pi, which is 32bit, but yeah it's a brand new Ryzen machine, it's 64 bit.

    I'll have to come back to this later today, but thank you for that. I'll let you know what I find.



  • @aha_1980

    arch command on my desktop:
    x86_64

    the pi:
    armv7l


  • Qt Champions 2017

    @graniteDev

    Hmm...ok, maybe I missunderstood some of the instruction when it talked about 64bit. I assumed it was talking about the pi, which is 32bit

    Don't worry, as said, cross compiling is advanced stuff ;)

    arch command on my desktop:
    x86_64

    Ok, that proves it.



  • @graniteDev

    arch command on my desktop:
    x86_64

    If you're following the suggested RaspberryPi2EGLFS guide, in step #10 please pay attention to

    If your system is 64 bit you may also edit device option to:


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