cross compile QT6 configure -> packages not found

jgnoss

I'm on a native bullseye machine
building QT6.2 from git using the comiler and cross-compiler that comes packaged in bullseye

first I build QT for the host using

jgnoss@mav-dev:~/Devel/QT/qt_x86_64_build$ ../qt_git/configure -prefix /home/jgnoss/Devel/QT/qt_x86_64/6.2.0

configure, build and install worked fine

for cross-compile, I sshfs'd the targets rootfs to:
/home/jgnoss/Devel/bbb/sysroot
made a toolchain-file for cmake

cmake_minimum_required(VERSION 3.18)
include_guard(GLOBAL)

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)

set(TARGET_SYSROOT /home/jgnoss/Devel/bbb/sysroot)
set(CROSS_COMPILER /usr/arm-linux-gnueabihf)

set(CMAKE_SYSROOT ${TARGET_SYSROOT})

set(ENV{PKG_CONFIG_PATH} "")
set(ENV{PKG_CONFIG_LIBDIR} ${CMAKE_SYSROOT}/usr/lib/pkgconfig:${CMAKE_SYSROOT}/usr/share/pkgconfig)
set(ENV{PKG_CONFIG_SYSROOT_DIR} ${CMAKE_SYSROOT})

set(CMAKE_C_COMPILER /usr/bin/arm-linux-gnueabihf-gcc-10)
set(CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabihf-g++-10)

# set(QT_COMPILER_FLAGS "-march=armv7-a -mfpu=neon -mfloat-abi=hard")
# set(QT_COMPILER_FLAGS "-march=armv7-a -mtune=cortex-a9 -mfpu=neon")
#set(QT_COMPILER_FLAGS "-march=armv7-a -mfpu=neon")

set(QT_COMPILER_FLAGS_RELEASE "-O2 -pipe")
set(QT_LINKER_FLAGS "-Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed")

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

include(CMakeInitializeConfigs)

function(cmake_initialize_per_config_variable _PREFIX _DOCSTRING)
  if (_PREFIX MATCHES "CMAKE_(C|CXX|ASM)_FLAGS")
    set(CMAKE_${CMAKE_MATCH_1}_FLAGS_INIT "${QT_COMPILER_FLAGS}")

    foreach (config DEBUG RELEASE MINSIZEREL RELWITHDEBINFO)
      if (DEFINED QT_COMPILER_FLAGS_${config})
        set(CMAKE_${CMAKE_MATCH_1}_FLAGS_${config}_INIT "${QT_COMPILER_FLAGS_${config}}")
      endif()
    endforeach()
  endif()

  if (_PREFIX MATCHES "CMAKE_(SHARED|MODULE|EXE)_LINKER_FLAGS")
    foreach (config SHARED MODULE EXE)
      set(CMAKE_${config}_LINKER_FLAGS_INIT "${QT_LINKER_FLAGS}")
    endforeach()
  endif()

  _cmake_initialize_per_config_variable(${ARGV})
endfunction()

now in another directory y try to cross-compile for arm using

jgnoss@mav-dev:~/Devel/QT/qt_bbb_build$  ../qt_git/configure -sysroot /home/jgnoss/Devel/bbb/sysroot -qt-host-path /home/jgnoss/Devel/QT/qt_x86_64/6.2.0 -prefix /home/jgnoss/Devel/QT/qt_bbb -extprefix /home/jgnoss/Devel/QT/qt_bbb -DQT_BUILD_TOOLS_WHEN_CROSSCOMPILING=ON -- -DCMAKE_TOOLCHAIN_FILE=/home/jgnoss/Devel/QT/toolchain-cross_armhf.cmake

configure runs fine, but misses to detect packages/libraries that are installed on the target

for example:
output from configure

-- Checking for module 'libudev'
--   No package 'libudev' found

running on target

jgnoss@beaglebone:~$ dpkg -l |grep libudev
ii  libgudev-1.0-0:armhf                      232-2                                 armhf        G
Object-based wrapper library for libudev
ii  libudev-dev:armhf                         241-7~deb10u8                         armhf        l
ibudev development files
ii  libudev1:armhf                            241-7~deb10u8                         armhf        l
ibudev shared library

jgnoss@beaglebone:~$ pkg-config --libs libudev
-ludev

that's just one example, there are a lot of packages/libraries that are not detected

any ideas how to solve that?

thanks
Ju

SGaist

Hi,

Did you install the dev packages of the dependencies on your target ?

jgnoss

@jgnoss said in cross compile QT6 configure -> packages not found:

ii libudev-dev:armhf

yes, that's the dev package

jgnoss

Is there a way to find out how configure is looking for libs and packages?

like --debug-trycompile when checking for compiled stuff

SGaist

AFAIK, cmake writes logs of its process. You should parse them.

jgnoss

OK, found the quirk.

Digging into configure logfiles it seemed configure isn't using pkg-config or at least not the right way.

So I added -pkg-config to my configure options, but still no libraries/packages found.

A closer look at pkg-config docs and cross compile options I came to conclusion that there is something wrong with where pck-config is looking for the .pc files.

QT's example cmake language file at this page set some values for pkg-config that seems to be right, but it came out that it somehow conflicts with what configure internally does.

Commenting out that following lines solved the problem and all libraries/packages where found.

# set(ENV{PKG_CONFIG_PATH} "")
# set(ENV{PKG_CONFIG_LIBDIR} ${CMAKE_SYSROOT}/usr/lib/pkgconfig:${CMAKE_SYSROOT}/usr/share/pkgconfig)
# set(ENV{PKG_CONFIG_SYSROOT_DIR} ${CMAKE_SYSROOT})

jgnoss

Sorry forgot to mark the link to the cmake language file from qt

here it is .

jgnoss

and another sorry, it's the toolchain file, not the language file