Cross-compilation on PC/UBUNTU for target PANDABOARD/UBUNTU.

[reme]

Hello,

I discover this forum during the building of my first Qt application. It is the first time I use it.
I cross compile a Qt project on a PC/UBUNTU for the target : PANDABOARD/UBUNTU.
I obtain a binary and run it on the PANDABOARD.
I obtain the following message :
"Could not find the Qt platform xcb"
After reading some articles in qt-project.org, I understand I need to generate the dynamic library libxcb.so.1 on my PC/UBUNTU for the PANDABOARD/UBUNTU.
Please, could you help me to cross compile this library on my PC/UBUNTU ?

Best regards.

[SGaist]

Hi and welcome to devnet,

Since your PandaBoard runs ubuntu, why not use the package manager from it to install the missing libraries ?

[reme]

Hi

Thanks for your answer.

I specify the complete message after running :

This application failed to start because it could not find or load the Qt platform plugin "xcb".Reinstalling the application may fix this problem. Aborted (core dumped)

I think the xcb package is already present on my target PANDABOARD/UBUNTU.
Indeed, the result of the command

sudo apt-cache pkgnames | grep xcb is :
libxcb-doc

libxcb-image0

libxcb-sync0

libxcb-render-util0

libxcb-dpms0

libxcb-glx0-dbg

libxcb-glx0-dev

libxcb-xprint0

libxcb-icccm4-dev

libxcb-xinerama0-dbg

libxcb-keysyms1

libxcb-xinerama0-dev

libxcb-xevie0-dbg

libxcb-shm0-dbg

libxcb-icccm4

libxcb-composite0-dbg

libxcb-xevie0-dev

libxcb-shm0-dev

libxcb-composite0-dev

libxcb-dri2-0-dbg

libxcb-dri2-0-dev

libxcb-xv0

libxcb-screensaver0-dbg

libxcb-glx0

libxcb-screensaver0-dev

libxcb-xevie0

libxcb-xfixes0

libxcb-sync0-dbg

python-xcbgen

libxcb-sync0-dev

libx11-xcb1

libxcb-util0

libxcb-keysyms1-dev

libxcb-xvmc0

libxcb-render0

libxcb-damage0-dbg

libxcb-damage0-dev

libxcb-res0-dbg

libxcb-res0-dev

libxcb1

libxcb-shape0-dbg

libxcb-shape0-dev

libx11-xcb-dev

libxcb-render-util0-dev

libxcb-damage0

libxcb-shape0

xcb-proto

libxcb-randr0-dbg

libxcb-randr0-dev

libxcb-xinerama0

libx11-xcb1-dbg

libxcb-randr0

libxcb-composite0

libxcb-xv0-dbg

libxcb-xv0-dev

xcb

libxcb-dpms0-dbg

libxcb-dpms0-dev

libxcb-ewmh1

libxcb-dri2-0

libxcb-xf86dri0-dbg

libxcb-xf86dri0-dev

libxcb-xf86dri0

libxcb-res0

libxcb-util0-dev

libxcb-xfixes0-dbg

libxcb-render0-dbg

libxcb-xfixes0-dev

libxcb-record0-dbg

libxcb-render0-dev

libxcb-record0

libxcb-xvmc0-dbg

libxcb-record0-dev

libxcb1-dbg

libxcb-xvmc0-dev

libxcb1-dev

libxcb-shm0

libxcb-xtest0

libxcb-xtest0-dbg

libxcb-xtest0-dev

libxcb-image0-dev

libxcb-ewmh1-dev

libxcb-screensaver0

libxcb-xprint0-dbg

libxcb-xprint0-dev

Best regards.

[SGaist]

Did you also installed the Qt dlls along with your application ?

[reme]

No because my target is PANDABOARD / UBUNTU.
After reading the deployment documentation it seems I need to compile the pluggin "xcb" :

but I am not able to produce the xcb dynamic library.

In the following directory :
qt-everywhere-opensource-src-5.2.1/qtbase/src/plugins/platforms/xcb

cd ../xcbplugins
make clean
qmake -config release
make

Do you agree with this approach ?

Thanks and best regards.

[SGaist]

Before compiling anything, did you also deploy the Qt 5 plugins ?

[reme]

Yes I deployed Qt 5 plugins (qtbase/plugins/platforms) on my target in the directory ./platforms.
But I think the xcb pluggin is lacked.
By running my application with gdb on my target I obtained the following message:

This application failed to start because it could not find or load the Qt platform plugin “xcb”.
Available platform pluggins are: linuxfb(from ./platforms), minimal (from ./platforms), offsreen (from ./platforms).

The error message is produced by QGuiApplicationPrivate::createPlatformIntegration() function

So, I think there is a problem because the xcb platform is not present in
qtbase/plugins/platforms.

Do you agree ?

Thanks.

[SGaist]

If it wasn't already built, it means that the test for it failed.

Do a new configure and force the use of xcb, you'll probably see it failed stating that the needed libraries/headers where not found. If it's the case, you are missing the necessary dev packages for it

[reme]

Hi,

Indeed there are problems during the new configure with -xcb.
I read src/plugins/platforms/xcb/README and install all the dependency packages for libxcb.
I found all the libraries thanks to the following command :
sudo apt-cache pkgnames | grep "libxcb*"

So, I do not understand why the last 3 lines of the message :
"The test for linking against libxcb failed!
You might need to install dependency packages for libxcb.
See src/plugins/platforms/xcb/README"

The result of the configure command is the following :
Sorry for the size of the message but I am not able to specify which piece of information is important.

./configure -xcb -v -prefix /home/stimg/QT/qt-everywhere-opensource-src-5.2.1/qtbase -skip connectivity -qreal float -nomake tests -nomake examples -opensource -xplatform linux-arm-gnueabi-g++

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
BEGIN MESSAGE
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

DEFAULT_LIBDIRS="/usr/lib/gcc/arm-linux-gnueabihf/4.6
/usr/lib/gcc/arm-linux-gnueabihf/lib
Creating qmake...
make: Nothing to be done for `first'.
Running configuration tests...
Warning: Disabling pkg-config since PKG_CONFIG_LIBDIR is not set.
Warning: Disabling pkg-config since PKG_CONFIG_SYSROOT_DIR is not set.
Determining architecture... ()
arm-linux-gnueabihf-g++-4.6 -c -pipe -g -Wall -W -fPIE -I../../mkspecs/linux-arm-gnueabi-g++ -I. -o arch.o arch.cpp
arm-linux-gnueabihf-g++-4.6 -o arch arch.o
/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 i386linux elf_l1om elf_k1om
collect2: ld returned 1 exit status
make: *** [arch] Error 1
Unable to determine architecture!

Could not determine the target architecture!
Turn on verbose messaging (-v) to see the final report.
Determining architecture... ()
g++ -c -pipe -g -Wall -W -fPIE -I../../mkspecs/linux-g++ -I. -o arch.o arch.cpp
g++ -o arch arch.o
{ test -n "" && DESTDIR="" || DESTDIR=.; } && test $(gdb --version | sed -e 's,[^0-9][^0-9]([0-9]).([0-9]).,\1\2,;q') -gt 72 && gdb --nx --batch --quiet -ex 'set confirm off' -ex "save gdb-index $DESTDIR" -ex quit 'arch' && test -f arch.gdb-index && objcopy --add-section '.gdb_index=arch.gdb-index' --set-section-flags '.gdb_index=readonly' 'arch' 'arch' && rm -f arch.gdb-index || true
Found architecture in binary
CFG_HOST_ARCH="x86_64"
CFG_HOST_CPUFEATURES=" mmx sse sse2"
System architecture: 'unknown'
Host architecture: 'x86_64'
C++11 auto-detection... ()
arm-linux-gnueabihf-g++-4.6 -c -pipe -O2 -std=c++0x -Wall -W -fPIE -I../../../mkspecs/linux-arm-gnueabi-g++ -I. -o c++11.o c++11.cpp
arm-linux-gnueabihf-g++-4.6 -Wl,-O1 -o c++11 c++11.o
/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 i386linux elf_l1om elf_k1om
collect2: ld returned 1 exit status
make: *** [c++11] Error 1
C++11 disabled.
floatmath auto-detection... ()
arm-linux-gnueabihf-g++-4.6 -c -pipe -O2 -Wall -W -fPIE -I../../../mkspecs/linux-arm-gnueabi-g++ -I. -o floatmath.o floatmath.cpp
floatmath.cpp:44:5: warning: unused parameter ‘argc’ [-Wunused-parameter]
floatmath.cpp:44:5: warning: unused parameter ‘argv’ [-Wunused-parameter]
arm-linux-gnueabihf-g++-4.6 -Wl,-O1 -o floatmath floatmath.o
/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi

...

evdev disabled.
XLib auto-detection... ()
arm-linux-gnueabihf-g++-4.6 -c -pipe -O2 -Wall -W -fPIE -I../../../mkspecs/linux-arm-gnueabi-g++ -I. -o xlib.o xlib.cpp
arm-linux-gnueabihf-g++-4.6 -Wl,-O1 -o xlib xlib.o -lXext -lX11 -lm
/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 i386linux elf_l1om elf_k1om
collect2: ld returned 1 exit status
make: *** [xlib] Error 1
XLib disabled.
xcb auto-detection... ()
arm-linux-gnueabihf-g++-4.6 -c -pipe -O2 -Wall -W -fPIE -I../../../mkspecs/linux-arm-gnueabi-g++ -I. -o xcb.o xcb.cpp
xcb.cpp: In function ‘int main(int, char**)’:
xcb.cpp:47:23: warning: unused variable ‘t’ [-Wunused-variable]
arm-linux-gnueabihf-g++-4.6 -Wl,-O1 -o xcb xcb.o -lxcb
/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 i386linux elf_l1om elf_k1om
collect2: ld returned 1 exit status
make: *** [xcb] Error 1
xcb disabled.
The test for linking against libxcb failed!
You might need to install dependency packages for libxcb.
See src/plugins/platforms/xcb/README.
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
END MESSAGE
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

[SGaist]

You need the arm version of these libraries

[reme]

Hi

I put all the xcb libraries loaded on my PANDABOARD/UBUNTU described in the README in the directory :
/usr/lib/gcc/arm-linux-gnueabihf/4.6 on my PC/UBUNTU.
But the result is always the same after the configuration :

xcb disabled.
The test for linking against libxcb failed! You might need to install dependency packages for libxcb. See src/plugins/platforms/xcb/README.

Best regards.

[SGaist]

You should rather point the configure script to the folder where the libraries can be found they have dependencies that might not be seen

[reme]

Hi

I modified the file /usr/lib/gcc/arm-linux-gnueabihf/4.6/pkgconfig/xcb.pc
thus I can specify the access to the static library libxcb.a (coming from my target). Nevertheless I obtain the same message :
arm-linux-gnueabihf-g++-4.6 -Wl,-O1 -o xcb xcb.o -L//usr/lib/gcc/arm-linux-gnueabihf/4.6 -lxcb

/usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 i386linux elf_l1om elf_k1om
collect2: ld returned 1 exit status
make: *** [xcb] Error 1
xcb disabled.
How must I resolve the problem /usr/bin/arm-linux-gnueabihf-ld: unrecognised emulation mode: armelf_linux_eabi ?

Best regards.

[SGaist]

Looking for that error, it seems you might be encountering a bug of gcc

[reme]

Hi

It seems there is not any solution to my problem.

Best regards.

[SGaist]

The only I see is to update gcc, is there not a more recent version available ?

[reme]

I do not find a more recent version but I find a workaround.
I am not sure to well understant it.
The workaround suggests to modify the configure.tgt file for the linker :

This is the linker target specific file. This is invoked by the autoconf generated configure script. Putting it in a separate shell file lets us skip running autoconf when modifying target specific.

The content of the config.tgt is the following :
--- ld/configure.tgt.orig 2011-04-05 20:22:23.000000000 +0000

                    targ_extra_emuls="armelfb armelf armelf_linux" 
                    targ_extra_libpath="armelf_linux" 
                    ;; 

-arm*--linux-eabi) targ_emul=armelf_linux_eabi
+arm--linux-eabi) targ_emul=armelf_linux_eabi
targ_extra_emuls=armelfb_linux_eabi
targ_extra_libpath=$targ_extra_emuls

                    targ_extra_emuls="armelf armelfb armelfb_linux" 
                    targ_extra_libpath="armelfb_linux" 
                    ;; 

-arm*--uclinuxeabi) targ_emul=armelf_linux_eabi
+arm*--uclinuxeabi*) targ_emul=armelf_linux_eabi
targ_extra_emuls=armelfb_linux_eabi
targ_extra_libpath=$targ_extra_emuls
;;

For me I need to compile the loader arm-linux-gnueabi-g++-4.6 by using the previous file.

Do you agree ?

Thanks and best regards.

[SGaist]

Worth to try