CMake 找不到 OpenCV 库

Question

与此 question 类似，我在 OS X 10.10.3 上使用 OpenCV 和 CMake 时遇到问题。

经过一番折腾，我终于在我的系统上构建了 OpenCV 3.0 beta； headers 现在位于 /usr/local/include 中，而库——正如它们应该的那样——位于 /usr/local/lib 中。我有一些使用 OpenCV 的小程序，我的 CMakeLists.txt 看起来像这样

set( CMAKE_CXX_FLAGS         "-O3 -w" ) 
find_package( OpenCV REQUIRED )
if(OpenCV_FOUND)
   message("Found OpenCV")
   message("Includes: " ${OpenCV_INCLUDE_DIRS})
endif(OpenCV_FOUND)

add_executable( cannyDetector canny/canny.cpp )

target_link_libraries( cannyDetector ${OpenCV_LIBS} )

我得到了通常的

Undefined symbols for architecture x86_64:
  "vtable for cv::_InputArray", referenced from:
      _main in correctImage.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for cv::_OutputArray", referenced from:
      _main in correctImage.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make[2]: *** [correctImage] Error 1
make[1]: *** [CMakeFiles/correctImage.dir/all] Error 2
make: *** [all] Error 2

变量OpenCV_LIBS包含

opencv_xphoto;opencv_xobjdetect;opencv_ximgproc;opencv_xfeatures2d;opencv_tracking;opencv_text;opencv_surface_matching;opencv_saliency;opencv_rgbd;opencv_reg;opencv_optflow;opencv_line_descriptor;opencv_latentsvm;opencv_ccalib;opencv_bioinspired;opencv_bgsegm;opencv_adas;opencv_videostab;opencv_videoio;opencv_video;opencv_ts;opencv_superres;opencv_stitching;opencv_shape;opencv_photo;opencv_objdetect;opencv_ml;opencv_imgproc;opencv_imgcodecs;opencv_highgui;opencv_hal;opencv_flann;opencv_features2d;opencv_core;opencv_calib3d

此外，手动编译有效：

gcc -o canny $(pkg-config --cflags opencv3)  $(pkg-config --libs opencv3) -lstdc++ -w -O3  ../canny/canny.cpp

（我不知道为什么我必须指定 -lstdc++，但如果没有它，linking 会因其他原因而失败）。当运行宁make VERBOSE=1时，以下命令为运行可执行文件：

/opt/local/bin/g++   -O3 -w -lstdc++ -Wl,-search_paths_first -Wl,-headerpad_max_install_names  CMakeFiles/cannyDetector.dir/canny/canny.o  -o cannyDetector  /usr/local/lib/libopencv_xphoto.3.0.0.dylib /usr/local/lib/libopencv_ximgproc.3.0.0.dylib /usr/local/lib/libopencv_tracking.3.0.0.dylib /usr/local/lib/libopencv_text.3.0.0.dylib /usr/local/lib/libopencv_surface_matching.3.0.0.dylib /usr/local/lib/libopencv_saliency.3.0.0.dylib /usr/local/lib/libopencv_rgbd.3.0.0.dylib /usr/local/lib/libopencv_reg.3.0.0.dylib /usr/local/lib/libopencv_optflow.3.0.0.dylib /usr/local/lib/libopencv_line_descriptor.3.0.0.dylib /usr/local/lib/libopencv_latentsvm.3.0.0.dylib /usr/local/lib/libopencv_ccalib.3.0.0.dylib /usr/local/lib/libopencv_bioinspired.3.0.0.dylib /usr/local/lib/libopencv_bgsegm.3.0.0.dylib /usr/local/lib/libopencv_adas.3.0.0.dylib /usr/local/lib/libopencv_videostab.3.0.0.dylib /usr/local/lib/libopencv_ts.a /usr/local/lib/libopencv_superres.3.0.0.dylib /usr/local/lib/libopencv_stitching.3.0.0.dylib /usr/local/lib/libopencv_photo.3.0.0.dylib /usr/local/lib/libopencv_objdetect.3.0.0.dylib /usr/local/lib/libopencv_hal.a /usr/local/lib/libopencv_xobjdetect.3.0.0.dylib /usr/local/lib/libopencv_xfeatures2d.3.0.0.dylib /usr/local/lib/libopencv_shape.3.0.0.dylib /usr/local/lib/libopencv_video.3.0.0.dylib /usr/local/lib/libopencv_calib3d.3.0.0.dylib /usr/local/lib/libopencv_features2d.3.0.0.dylib /usr/local/lib/libopencv_ml.3.0.0.dylib /usr/local/lib/libopencv_highgui.3.0.0.dylib /usr/local/lib/libopencv_videoio.3.0.0.dylib /usr/local/lib/libopencv_imgcodecs.3.0.0.dylib /usr/local/lib/libopencv_imgproc.3.0.0.dylib /usr/local/lib/libopencv_flann.3.0.0.dylib /usr/local/lib/libopencv_core.3.0.0.dylib /usr/local/lib/libopencv_hal.a -framework AGL -framework OpenGL /usr/local/share/OpenCV/3rdparty/lib/libippicv.a

但是，如果我执行命令并将输入文件 CMakeFiles/cannyDetector.dir/canny/canny.o 替换为输入源文件 ../canny/canny.cpp，它就可以工作！

所以库都在那里，但它仍然无法编译，因为编译器无法 link object 文件，但一步编译和 linking 工作。

谁能告诉我这是怎么回事？

Answer 1

我的解决方法是指示 CMake 在何处查找 OpenCV 配置模块。

find_package(OpenCV REQUIRED PATHS /usr/local/share/OpenCV NO_DEFAULT_PATH) # manual specification of the OpenCVConfig.cmake path is necessary since otherwise, cmake assigns /opt/local a higher priority and ocv2.4 will be used

不知为何，/opt/local/share 的优先级高于 /usr/local/share，因此只找到了 OpenCV 2.4 的配置文件，但我使用的是 3.0。我不确定是什么原因导致链接错误，但可能某些代码已从库移动到 3.0 版中的 headers 必须与用户代码一起编译，但不是因为 CMake 仅包含版本 2 headers.

还有

include_directories(${OpenCV_INCLUDE_DIRS})

丢失了。

CMake 找不到 OpenCV 库

CMake does not find OpenCV libraries

c++

linker

opencv

makefile

cmake