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Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: None
Affects Version/s: 6.0
Component/s: Build System: CMake
Labels:
- cmake_qt6
- cmake_switch_requirement

Epic Link:
CMake Port: Milestone Done

Description

If you try to build standalone tests of qtbase, or just qtsvg targeting armv7 using the boot2qt 2.7.2 SDK, it fails at cmake configure time with the following error:

../qtbase_built_developer_armv7/bin/qt-cmake-private ../qtsvg
-- The CXX compiler identification is GNU 8.3.0
-- The C compiler identification is GNU 8.3.0
-- Check for working CXX compiler: /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-g++
-- Check for working CXX compiler: /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-g++ - broken
CMake Error at /home/alex/Dev/cmakes/src/Modules/CMakeTestCXXCompiler.cmake:53 (message):
  The C++ compiler

    "/opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-g++"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: /home/alex/Dev/qt/qt5_cmake/qtsvg_built_developer_armv7/CMakeFiles/CMakeTmp

    Run Build Command(s):/opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/bin/ninja cmTC_a2ec2 && [1/2] Building CXX object CMakeFiles/cmTC_a2ec2.dir/testCXXCompiler.cxx.o
    [2/2] Linking CXX executable cmTC_a2ec2
    FAILED: cmTC_a2ec2
    : && /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-g++ --sysroot=/opt/b2qt/2.7.2/sysroots/armv7at2hf-neon-poky-linux-gnueabi -O2 -pipe -g -feliminate-unused-debug-types -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed CMakeFiles/cmTC_a2ec2.dir/testCXXCompiler.cxx.o -o cmTC_a2ec2   && :
    /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/libexec/arm-poky-linux-gnueabi/gcc/arm-poky-linux-gnueabi/8.3.0/ld: error: cmTC_a2ec2 uses VFP register arguments, CMakeFiles/cmTC_a2ec2.dir/testCXXCompiler.cxx.o does not
    /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/libexec/arm-poky-linux-gnueabi/gcc/arm-poky-linux-gnueabi/8.3.0/ld: failed to merge target specific data of file CMakeFiles/cmTC_a2ec2.dir/testCXXCompiler.cxx.o
    collect2: error: ld returned 1 exit status
    ninja: build stopped: subcommand failed.

  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:5 (project)

The issue is that the boot2qt sdk cmake toolchain file has the piece of code:

$ cat /opt/b2qt/2.7.2/sysroots/x86_64-pokysdk-linux/usr/share/cmake/OEToolchainConfig.cmake
# ....
# Include the toolchain configuration subscripts
file( GLOB toolchain_config_files "${CMAKE_TOOLCHAIN_FILE}.d/*.cmake" )
foreach(config ${toolchain_config_files})
    include(${config})
endforeach()

It wants to load additional files (like qemuarmv7.cmake) which sets various compile and link flags.

This fails for us because CMAKE_TOOLCHAIN_FILE is not the path for "OEToolchainConfig.cmake" but rather the qt toolchain that we generate which chain loads "OEToolchainConfig.cmake".

CMAKE_TOOLCHAIN_FILE thus evaluates to "qt.toolchain.cmake" and none of the sdk specific files like qemuarmv7.cmake are loaded, causing a failure to compile even a simple cmake app.

The proper way would be to fix the code to use CMAKE_CURRENT_LIST_FILE instead, push that upstream, create a new boot2qt sdk, provision it in our VMs, and use that.
Last provisioning of b2qt was done in https://codereview.qt-project.org/c/qt/qt5/+/286213