C++可執行文件鏈接問題

Question

嗯，這真的讓我現在有幾個小時:)

我有一個C++項目，它使用cmake。我有鏈接問題，我無法解決。下面是隻有一個最終可執行文件的鏈接命令：

/usr/bin/c++ -std=c++0x CMakeFiles/calib_sfm.dir/calib_sfm.cpp.o \ 
    -o calib_sfm -rdynamic libviso.so -lboost_log -lboost_log_setup \ 
    -lboost_system -lboost_filesystem -lboost_thread -lpthread \ 
    /home/kreimer/opencv3.0/lib/libopencv_viz.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_videostab.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_video.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_ts.a \ 
    /home/kreimer/opencv3.0/lib/libopencv_superres.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_stitching.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_softcascade.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_shape.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_photo.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_optim.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_objdetect.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_nonfree.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_ml.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_legacy.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_imgproc.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_highgui.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_flann.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_features2d.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudawarping.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudastereo.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudaoptflow.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudaimgproc.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudafilters.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudafeatures2d.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudacodec.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudabgsegm.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudaarithm.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cuda.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_core.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_contrib.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_calib3d.so.3.0.0 \ 
    -ldl -lm -lpthread -lrt \ 
    /home/kreimer/opencv3.0/share/OpenCV/3rdparty/lib/libippicv.a \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudawarping.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_legacy.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudaimgproc.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudafilters.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_video.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_objdetect.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_nonfree.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_ml.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_cudaarithm.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_calib3d.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_features2d.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_highgui.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_imgproc.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_flann.so.3.0.0 \ 
    /home/kreimer/opencv3.0/lib/libopencv_core.so.3.0.0 \ 
    -Wl,-rpath,/home/kreimer/alex.kreimer@gmail.com/Technion/projects/robil/viso/debug/src:/home/kreimer/opencv3.0/lib 

產生這樣的：

libviso.so: undefined reference to `cv::DescriptorExtractor::compute(cv::_InputArray const&, std::vector<cv::KeyPoint, std::allocator<cv::KeyPoint> >&, cv::_OutputArray const&) const' 
libviso.so: undefined reference to `cv::calcHist(cv::Mat const*, int, int const*, cv::_InputArray const&, cv::_OutputArray const&, int, int const*, float const**, bool, bool)' 
libviso.so: undefined reference to `cv::DescriptorExtractor::~DescriptorExtractor()' 
libviso.so: undefined reference to `cv::namedWindow(cv::String const&, int)' 
libviso.so: undefined reference to `cv::flann::SearchParams::SearchParams(int, float, bool)' 
libviso.so: undefined reference to `cv::computeCorrespondEpilines(cv::_InputArray const&, int, cv::_InputArray const&, cv::_OutputArray const&)' 
libviso.so: undefined reference to `cv::DescriptorExtractor::~DescriptorExtractor()' 
libviso.so: undefined reference to `cv::destroyWindow(cv::String const&)' 
libviso.so: undefined reference to `cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector<int, std::allocator<int> > const&)' 
libviso.so: undefined reference to `cv::imread(cv::String const&, int)' 
libviso.so: undefined reference to `cv::cornerHarris(cv::_InputArray const&, cv::_OutputArray const&, int, int, double, int)' 
libviso.so: undefined reference to `cv::FeatureDetector::detect(cv::_InputArray const&, std::vector<cv::KeyPoint, std::allocator<cv::KeyPoint> >&, cv::_InputArray const&) const' 
libviso.so: undefined reference to `cv::waitKey(int)' 
libviso.so: undefined reference to `cv::findEssentialMat(cv::_InputArray const&, cv::_InputArray const&, double, cv::Point_<double>, int, double, double, cv::_OutputArray const&)' 
libviso.so: undefined reference to `cv::cvtColor(cv::_InputArray const&, cv::_OutputArray const&, int, int)' 
libviso.so: undefined reference to `cv::FeatureDetector::~FeatureDetector()' 
libviso.so: undefined reference to `typeinfo for cv::FeatureDetector' 
libviso.so: undefined reference to `cv::Sobel(cv::_InputArray const&, cv::_OutputArray const&, int, int, int, int, double, double, int)' 
libviso.so: undefined reference to `cv::FeatureDetector::empty() const' 
libviso.so: undefined reference to `cv::undistortPoints(cv::_InputArray const&, cv::_OutputArray const&, cv::_InputArray const&, cv::_InputArray const&, cv::_InputArray const&, cv::_InputArray const&)' 
libviso.so: undefined reference to `cv::DescriptorExtractor::empty() const' 
libviso.so: undefined reference to `cv::FeatureDetector::~FeatureDetector()' 
libviso.so: undefined reference to `cv::FeatureDetector::~FeatureDetector()' 
libviso.so: undefined reference to `typeinfo for cv::DescriptorExtractor' 
libviso.so: undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)' 
libviso.so: undefined reference to `cv::flann::IndexParams::~IndexParams()' 
libviso.so: undefined reference to `cv::DescriptorExtractor::~DescriptorExtractor()' 

鑑於缺少的標誌之一是CV :: namedWindow我這樣做：

nm -gC /home/kreimer/opencv3.0/lib/libopencv_highgui.so.3.0.0 | grep namedWindow 
000000000002df80 T cv::namedWindow(cv::String const&, int) 

所以符號出現在提供的共享庫中。當我閱讀圖書館的順序並不重要的動態構建，那麼可能是什麼問題？順便說一句，如果我將libviso的版本更改爲靜態而不是動態，如上所示，此可執行文件鏈接就好了。

Answer 1

用Unix風格的鏈接器，鏈接命令行的順序總是很重要。所有目標文件，.a文件，.so文件和-l選項都嚴格按照從左到右的順序進行處理。每個項目只能爲其左側的項目解析未定義的符號。您可能誤解了文檔，這實際上是在討論鏈接器人員拒絕修復的相關錯誤（一直回到Solaris 2.0，iirc），其中共享庫是無條件包含的，而靜態庫不是。

但是，這不是唯一的問題，因爲libviso.so是命令行中的第一件事情之一。我懷疑你有什麼是錯誤消息，其中未定義的符號正在被libviso.so使用，並且在命令行上還有其他更多的內容，但是它們被歸於而僅歸於libviso.so。

有一個簡單的大鐵錘的解決辦法：安排，讓您的命令行如下：

/usr/bin/c++ -std=c++0x CMakeFiles/calib_sfm.dir/calib_sfm.cpp.o -o calib_sfm \ 
    -rdynamic -Wl,--as-needed -Wl,--group \ 
    $(ALL_THE_LIBRARIES_HERE) \ 
    -Wl,--end-group \ 
    -Wl,-rpath,$(SAME_RPATH_AS_BEFORE) 

的-Wl,--group ... -Wl,--end-group建設強制鏈接器掃描一遍又之間的一切之前，反覆它或者已經解決了所有的未定義的符號，或者可以確定地證明它不能完成。添加-Wl,--as-needed修復了我之前提到的錯誤，所以你不會吮吸你實際上沒有使用的庫。

Answer 2

我以前遇到過幾個類似的問題;我不記得具體的例子，但我很清楚地記得圖書館的順序很重要;我結束了洗牌，直到我的項目最終適當建成。