Need to build twice to copy all dependencies in post build step

cen · March 20, 2025, 3:44pm

I have a root cmake project consisting of two subprojects, one is a library, the other are unit tests. Unit tests link to the library.

On Windows, I need to copy all dependend .dll-s for shared builds next to the unit test .exe for it to be able to run.

I do this with the following logic seen here:

github.com/stachenov/quazip

qztest/CMakeLists.txt

master


      
              ${QUAZIP_TEST_QT_LIBRARIES}
              QuaZip::QuaZip
          )
          
          add_test(NAME qztest_all
          	COMMAND qztest
          	WORKING_DIRECTORY ${QUAZIP_BINARY_DIR}/quazip # preliminary hack to find the dll on windows
          )
          add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} --verbose DEPENDS qztest)
          
          if (WIN32 AND BUILD_SHARED_LIBS)
          	message(STATUS "Setting up windeployqt")
          	set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake")
          	include(windeployqt)
          	windeployqt(qztest)
          
              # This copies quazip1-qt6.dll .dll, zlib1.dll and bz2.dll.
              # For an unknown reason, bz2.dll is copied on second build only. :insert thinking emoji:
              add_custom_command(
                  TARGET qztest POST_BUILD
                  COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_RUNTIME_DLLS:qztest> $<TARGET_FILE_DIR:qztest>

Since this is a Qt project, I first run windeployqt which is the recommended way to gather all necessary Qt dependencies.
Then, three remaining dependencies need to be copied, zlib, bz2 and the tested library itself. I do that with custom command and $<TARGET_RUNTIME_DLLS:qztest> (it was incredibly hard to track this down in the first place).

This almost works with a bizarre problem that bz2 is only copied if I run cmake build a second time. What could possibly cause this? Some kind of a race condition? I am all out of ideas.

Here is the workaround

github.com/stachenov/quazip

.github/workflows/reusable-win.yml

master


      
          
          - name: Configure
            shell: cmd
            run: cmake --preset ${{ inputs.preset }} -DQUAZIP_ENABLE_TESTS=ON
          
          - name: Build
            shell: cmd
            run: cmake --build ${{github.workspace}}/build --config Release
          
          # This second build is here temporarily until we figure out why qztest dep .dlls are not copied after first build
          - name: Build 2
            shell: cmd
            run: cmake --build ${{github.workspace}}/build --config Release
          
          - name: Check PE
            shell: bash
            working-directory: ./build/quazip/Release
            run: |
              DLL_NAME="quazip1-qt${{ startsWith(inputs.qt_version, '6') && '6' || '5' }}.dll"
              file "$DLL_NAME"
              file "$DLL_NAME" |grep "${{ inputs.pe_str }}"

LegalizeAdulthood · March 20, 2025, 9:22pm

This sounds to me like a missing dependency relationship.

This looks to me like it should be part of your post-build script.

cen · March 20, 2025, 10:21pm

It is part of the post deploy, defined in cmake/windeployqt.cmake

Now that you mention it, it does seem that bzip is not added into target libraries the same way as zlib is so there might be something about that. I’ll look into it. I think I was too surprised about the fact that it was copied on second build to check if there are any differences from other dependencies that work on first try.

LegalizeAdulthood · March 21, 2025, 3:29pm

Qt is, and always has been, a bit of a mess. Did you try asking in a Qt forum?