CMake对pthread_key_create的未定义引用

如何解决CMake对pthread_key_create的未定义引用

我有一个CMake项目。这是一些相关的行：

    set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
    set(THREADS_PREFER_PTHREAD_FLAG TRUE)
    find_package(Threads required)
    message("[temp] threads stuff Threads_FOUND=${Threads_FOUND} in Threads_DIR=${Threads_DIR}")
    if(TARGET Threads::Threads)
      message("[temp] Yep")
    else()
      message("[temp] nope")
    endif()

我可以在控制台中看到已找到线程库，并且Threads :: Threads目标存在。但是Threads_DIR为空！

    [temp] threads stuff Threads_FOUND=TRUE in Threads_DIR=
    [temp] Yep

某些目标链接到Threads :: Threads。

add_executable(ETestOnline ETestOnline.cpp)

target_link_libraries(ETestOnline
  PRIVATE
    Threads::Threads
    ${extra_libs}
)

这是我得到的输出：

   [12/33] Linking CXX executable test/integration/ETestOnline
    Failed: test/integration/ETestOnline 
    : && /usr/bin/clang++-9 -O2 -g -DNDEBUG  test/integration/CMakeFiles/ETestOnline.dir/ETestOnline.cpp.o -o test/integration/ETestOnline  -Wl,-rpath,/opt/opencv/lib:/opt/boost/lib  _deps/mycode-common-build/libmycode-common-core.a  _deps/mycode-common-build/libmycode-common-image.a  _deps/mycode-common-build/libmycode-common-net.a  _deps/mycode-common-build/libmycode-common-video.a  liblegofw_common_nodes.a  _deps/mycode-common-build/libmycode-common-image.a  /opt/opencv/lib/libopencv_highgui.so.3.4.5  /opt/opencv/lib/libopencv_videoio.so.3.4.5  /opt/opencv/lib/libopencv_imgcodecs.so.3.4.5  /opt/opencv/lib/libopencv_imgproc.so.3.4.5  /opt/opencv/lib/libopencv_core.so.3.4.5  _deps/mycode-common-build/libmycode-common-net.a  _deps/mycode-common-build/libmycode-common-video.a  _deps/mycode-common-build/libmycode-common-core.a  /opt/boost/lib/libboost_random.so.1.70.0  /opt/boost/lib/libboost_system.so.1.70.0  _deps/spdlog-build/libspdlog.a  /usr/lib/x86_64-linux-gnu/libavformat.so  /usr/lib/x86_64-linux-gnu/libavcodec.so  /usr/lib/x86_64-linux-gnu/libavutil.so  /usr/lib/x86_64-linux-gnu/libswresample.so  /usr/lib/x86_64-linux-gnu/libswscale.so  /usr/lib/x86_64-linux-gnu/libavdevice.so  /usr/lib/x86_64-linux-gnu/libavfilter.so  /opt/boost/lib/libboost_random.so.1.70.0  /opt/boost/lib/libboost_system.so.1.70.0  /opt/opencv/lib/libopencv_highgui.so.3.4.5  /opt/opencv/lib/libopencv_videoio.so.3.4.5  /opt/opencv/lib/libopencv_imgcodecs.so.3.4.5  /opt/opencv/lib/libopencv_imgproc.so.3.4.5  /opt/opencv/lib/libopencv_core.so.3.4.5 && :
    /usr/bin/ld: test/integration/CMakeFiles/ETestOnline.dir/ETestOnline.cpp.o: undefined reference to symbol 'pthread_create@@GLIBC_2.2.5'
    //lib/x86_64-linux-gnu/libpthread.so.0: error adding symbols: DSO missing from command line
    clang: error: linker command Failed with exit code 1 (use -v to see invocation)
    ninja: build stopped: subcommand Failed.

任何想法可能有什么问题吗？谢谢！