[Link error]Cross-Compiling QT 5.14.2 To RPi4 failed.

Lak4CYUT

Hi Everyone,
I want to develop QT app on RPi4 and I hope I can use the ssh to develop and test my app.
According this guide https://wiki.qt.io/RaspberryPi2EGLFS and the comment on https://code.qt.io/cgit/qt/qtbase.git/tree/mkspecs/devices/linux-rasp-pi4-v3d-g++/qmake.conf?h=5.14.2.
My host is ubuntu 19.10.
The cross compiler is installed by APT.

cpp-9-arm-linux-gnueabihf/eoan,now 9.2.1-9ubuntu2cross1 amd64 [installed,automatic]
g++-9-arm-linux-gnueabihf/eoan,now 9.2.1-9ubuntu2cross1 amd64 [installed,automatic]
gcc-9-arm-linux-gnueabihf-base/eoan,now 9.2.1-9ubuntu2cross1 amd64 [installed,automatic]
gcc-9-arm-linux-gnueabihf/eoan,now 9.2.1-9ubuntu2cross1 amd64 [installed,automatic]

I write the configuration command below,

./configure -release -opengl es2 -device linux-rasp-pi4-v3d-g++ -device-option CROSS_COMPILE=arm-linux-gnueabihf- -sysroot /home/lake/Qt/raspi/sysroot -opensource -confirm-license -make libs -prefix /usr/local/qt5pi -extprefix /home/lake/Qt/raspi/qt5pi -v -no-use-gold-linker

But I cannot link succeed, it always throw the error like the following,

make[3]: Entering directory `/home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/tools/qmltime'
arm-linux-gnueabihf-g++ -mfloat-abi=hard --sysroot=/home/lake/Qt/raspi/sysroot -Wl,-O1 -Wl,--enable-new-dtags -Wl,-rpath,/usr/local/qt5pi/lib -Wl,-rpath-link,/home/lake/Qt/raspi/sysroot/usr/lib/arm-linux-gnueabihf -Wl,-rpath-link,/home/lake/Qt/raspi/sysroot/lib/arm-linux-gnueabihf -o qmltime .obj/qmltime.o   /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Quick.so /home/lake/Qt/qt-everywhere-src-5.14.1/qtbase/lib/libQt5Gui.so /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5QmlModels.so /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Qml.so /home/lake/Qt/qt-everywhere-src-5.14.1/qtbase/lib/libQt5Network.so /home/lake/Qt/qt-everywhere-src-5.14.1/qtbase/lib/libQt5Core.so -L/home/lake/Qt/raspi/sysroot/usr/lib/arm-linux-gnueabihf -lGLESv2 -lpthread   
/usr/lib/gcc-cross/arm-linux-gnueabihf/9/../../../../arm-linux-gnueabihf/bin/ld: /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Qml.so: undefined reference to `log2@GLIBC_2.29'
/usr/lib/gcc-cross/arm-linux-gnueabihf/9/../../../../arm-linux-gnueabihf/bin/ld: /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Qml.so: undefined reference to `pow@GLIBC_2.29'
/usr/lib/gcc-cross/arm-linux-gnueabihf/9/../../../../arm-linux-gnueabihf/bin/ld: /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Qml.so: undefined reference to `exp@GLIBC_2.29'
/usr/lib/gcc-cross/arm-linux-gnueabihf/9/../../../../arm-linux-gnueabihf/bin/ld: /home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/lib/libQt5Qml.so: undefined reference to `log@GLIBC_2.29'
collect2: error: ld returned 1 exit status
make[3]: *** [qmltime] Error 1
make[3]: Leaving directory `/home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/tools/qmltime'
make[2]: *** [sub-qmltime-make_first] Error 2
make[2]: Leaving directory `/home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative/tools'
make[1]: *** [sub-tools-make_first] Error 2
make[1]: Leaving directory `/home/lake/Qt/qt-everywhere-src-5.14.1/qtdeclarative'
make: *** [module-qtdeclarative-make_first] Error 2

It seems libQt5Qml.so is built by host libc (2.30), but when another library that link to libQt5Qml, it will go to use the libc from sysroot (or rpath?), but Raspberry Pi is only support to 2.28 so far.

Package: libc6
Version: 2.28-10+rpi1
Priority: optional
Section: libs
Source: glibc
Maintainer: GNU Libc Maintainers <debian-glibc@lists.debian.org>
Installed-Size: 9,198 kB
Depends: libgcc1
Recommends: libidn2-0 (>= 2.0.5~)
Suggests: glibc-doc, debconf | debconf-2.0, libc-l10n, locales
Conflicts: openrc (<< 0.27-2~)
Breaks: hurd (<< 1:0.5.git20140203-1), libtirpc1 (<< 0.2.3), locales (<< 2.28), locales-all (<< 2.28), nocache (<< 1.1-1~), nscd (<< 2.28), r-cran-later (<< 0.7.5+dfsg-2)

Could anyone help me or give me some suggestion? This problem is stuck me over 4 day....
Thanks a lot.

Lak4CYUT

I guess the problem is caused by that libQt5Qml.so be linked to host's libc (libstdc++ -> libm), but when other projects link to libQt5Qml.so, linker will go to reference --sysroot or -rpath specified path, and found the remote libc.
I don't know why, does anyone have any idea?? Thanks.

dare

I have the same problem with libQt5Qml.so. My host is Linux Ubuntu 20.04, Raspberry Pi 4. I try cross-compile Qt version 5.15.1. Have you dealt with this ?