Qt6 Raspberry Pi cross compliation error.

[H0rBIe]

Hello,

I also came across this problem. I tried compiling everything with the GCC 10 version which is installed on my RPI. I will give the older Linux version a try using an old Notebook. I am also not very deep into compiler dependencies, so hopefully this also works for me.

BR

[Kumi]

@rickiewars I have encountered all the problems mentioned in the thread. Your posts were very helpful, I managed to compile and run QT on my RPI4. The sysroot-relativelinks.py fixed the problem with dbus and upgrading the GCC on my rpi to gcc-11, solved the problem with undefined references.

[Dane 0]

@Kumi How did you upgrade to gcc-11 on your RPi? I've tried using the gcc10 cross compiler on Ubuntu 22.04 (sudo apt install gcc-10-aarch64-linux-gnu g++-10-aarch64-linux-gnu) however this didn't help.

[davethomas_again]

Same errors.

I used

symlinks -rc rpi-sysroot

Is sysroot-relativelinks.py different so that I need to use it instead?

Kumi,

How does changing the compiler on the rpi help? That won't change the libraries on the Bullseye distribution that seem to be the issue.

Thanks!

[davethomas_again]

@davethomas_again

There does seem to be a difference in what the symlinks (that's built into Ubuntu) does versus the sysroots-relativelinks.py script.

I deleted all the sysroot files, and redid the rsync. Deleted everything in the build folders and redid the configure.

It's still compiling---3000 out of 8066 files. I'm pretty sure that's beyond where it was failing for dbus issues.

I guess I'll get to the unresolved references issue. Is the theory that the libc needs to be rebuilt with a compatible compiler on the rpi, then rsync'ed back to the host machine? Obviously, nothing you do on the rpi will help the build on the host--unless you copy files over from the rpi into sysroot.

Right?

[davethomas_again]

Yes, same place.

Down to the link phase, now get the unresolved externals.

I tried /usr/bin/aarch64-linux-gnu-gcc-11 and -9. (and same g++). My rpi Bullseye has gcc and g++ 10.2.1 20210110.

So, one gcc release earlier and one later.

Anyone have a cross-compiler known to work?

[davethomas_again]

I've tried gcc-9, -10, and -11. I get the same unresolved externals at link time like this:

usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `_dl_make_stack_executable@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_dlclose@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_dlopen_mode@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_longjmp@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_allocate_rtsig_private@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_thread_freeres@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libdl.so.2: undefined reference to `_dl_addr@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_pthread_init@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_current_sigrtmin_private@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libdl.so.2: undefined reference to `_dl_sym@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_dlsym@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libpthread.so.0: undefined reference to `__libc_current_sigrtmax_private@GLIBC_PRIVATE'
/usr/lib/gcc-cross/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/bin/ld: /home/dave/rpi-sysroot/lib/aarch64-linux-gnu/libdl.so.2: undefined reference to `_dl_vsym@GLIBC_PRIVATE'
collect2: error: ld returned 1 exit status

@rickiewars

You said:

Downgrading to an Ubuntu 20.04 based distro solved this first issue for me

Do you know what gcc and g++ compiler you used? If I was sure that 20.04 would resolve, I'd start over. But, that's a lot of work and I think only the toolchain matters.

Thanks!

[Maxxi]

@Dane-0 I had the same problem with Ubuntu 22.04 and Qt6. Using gcc-11 on raspberry pi solved the issue. However, you need to cross compile the gcc-11 for the raspberry pi. To do so, first you need to set up a cross compiler using the same version of glibc, binutils, and gcc that you have on your raspberry pi system. This link is exactly what you need to do:
https://solarianprogrammer.com/2018/05/06/building-gcc-cross-compiler-raspberry-pi/

Follow the instruction in this tutorial exactly, and finally add these paths to your LD_LIBRARY_PATH variable on your pi:
/path/to/gcc-11/lib
/path/to/gcc-11/lib64

I hope this will help you.

[davethomas_again]

@Maxxi

Thanks!

I punted and downgraded to Ubuntu 20. When I get a chance, I'll try again on 22.

[Christian Niekler]

Is there any progress on this? Did anyone solve this? I am having the same issue. I am using the Cross-Compile Qt6 for Raspberry Pi documentation. Host Ubuntu 22.04, Target Raspberry Pi Bookworm. I can Build for the Host, and can also configure it for the Target without issues, but when I try to build it for target I always get the issue FAILED qtbase/libQt6DBus.so.6.5.3. I am using aarch64-linux-gnu-g++-11.

ninja --version
1.10.1
cmake --version
cmake version 3.28.20231020-g35c7e23 (self build)

EDIT:
On my Raspberry I have gcc --version -> 12.2.0. Maybe I should use the version 12 cross compiler as well.

[Nobuddy]

I'm aware this is ancient history but I was running into this problem as well (I've corrected it) and feel it necessary to add a bit more context and my analysis of what I think is happening. Tl;dr I was able to correct the aforementioned error by running the sysroot-relativesymlinks.py script mentioned above, re-running the configure, and rebuilding.

As noted previously, symlinks doesn't quite fix everything and I also had to use the Python symlink script. What I noticed, though, after running symlinks the first time is that a few shared libraries (such as Dbus) were not being correctly re-linked. Specifically:

aaron@AUSTIN:~$ ls -l rpi-sysroot/lib/aarch64-linux-gnu/libdbus*
-rw-r--r-- 1 aaron aaron 785514 Sep 16  2023 rpi-sysroot/lib/aarch64-linux-gnu/libdbus-1.a
lrwxrwxrwx 1 aaron aaron     42 Sep 16  2023 rpi-sysroot/lib/aarch64-linux-gnu/libdbus-1.so -> /lib/aarch64-linux-gnu/libdbus-1.so.3.32.4
lrwxrwxrwx 1 aaron aaron     19 Sep 16  2023 rpi-sysroot/lib/aarch64-linux-gnu/libdbus-1.so.3 -> libdbus-1.so.3.32.4
-rw-r--r-- 1 aaron aaron 395336 Sep 16  2023 rpi-sysroot/lib/aarch64-linux-gnu/libdbus-1.so.3.32.4

Notice how libdbus-1.so is still pointing to my system's (aarch64) version of libdbus, which also did not exist, since my system is x86_64 -- so the link itself was bad. So just a reminder to ensure that all of the links in your sysroot do not point to anything outside of that sysroot.

Hopefully this helps any Googler in the future.