使用 cmake 构建项目时出现 OpenCV 3.2.0 链接器错误答案

【问题标题】：OpenCV 3.2.0 linker error while building a project using cmake使用 cmake 构建项目时出现 OpenCV 3.2.0 链接器错误
【发布时间】：2019-09-04 01:49:07
【问题描述】：

我错误地删除了我的 /usr/local 文件夹，之后我不得不再次构建 OpenCV 和 Caffe。现在我的项目没有编译。每次我尝试使用 cmake 构建项目时，都会出现错误并停止进度。

[ 80%] Built target mygoturn
[ 80%] Linking CXX executable ../bin/runTracker
/usr/bin/ld: CMakeFiles/runTracker.dir/src/visualizer/runTracker.cpp.o: undefined reference to symbol '_ZN2cv6imreadERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEi'
//usr/local/lib/libopencv_imgcodecs.so.4.1: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
CMakeFiles/runTracker.dir/build.make:200: recipe for target '../bin/runTracker' failed
make[2]: *** [../bin/runTracker] Error 1
CMakeFiles/Makefile2:104: recipe for target 'CMakeFiles/runTracker.dir/all' failed
make[1]: *** [CMakeFiles/runTracker.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

我检查了命令 pkg-config --libs --cflags opencv 并得到以下回复：

-I/usr/include/opencv -lopencv_shape -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_datasets -lopencv_dpm -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hdf -lopencv_line_descriptor -lopencv_optflow -lopencv_video -lopencv_plot -lopencv_reg -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_rgbd -lopencv_viz -lopencv_surface_matching -lopencv_text -lopencv_ximgproc -lopencv_calib3d -lopencv_features2d -lopencv_flann -lopencv_xobjdetect -lopencv_objdetect -lopencv_ml -lopencv_xphoto -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_photo -lopencv_imgproc -lopencv_core

然后我将包含构建序列的 CMakeLists.txt 文件。

cmake_minimum_required(VERSION 3.6)
project(mygoturn)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
find_package(Boost COMPONENTS system filesystem regex REQUIRED)

# avoid "can not find -lopencv_dep_cudart"
set(CUDA_USE_STATIC_CUDA_RUNTIME OFF)

find_package( OpenCV REQUIRED )
message("Open CV version is ${OpenCV_VERSION}")

set(Caffe_DIR ~/tracking/GOTURN/caffe)
find_package(Caffe REQUIRED)
include_directories(${Caffe_INCLUDE_DIRS})
add_definitions(${Caffe_DEFINITIONS})    # ex. -DCPU_ONLY
message("Caffe_DIR is ${Caffe_DIR}")

set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin")

add_library (${PROJECT_NAME}

        src/network/regressor.cpp
        src/network/regressor_base.cpp
        src/tracker/tracker.cpp
        src/helper/helper.cpp
        src/helper/bounding_box.cpp
        src/helper/image_proc.cpp

        src/network/regressor.h
        src/network/regressor_base.h
        src/tracker/tracker.h
        src/helper/helper.h
        src/helper/bounding_box.h
        src/helper/image_proc.h
       )

include_directories(src)

set(SOURCE_FILES src/visualizer/runTracker.cpp src/loader/loader_base.cpp src/loader/loader_base.h)
add_executable(runTracker ${SOURCE_FILES})
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS} ${Caffe_LIBRARIES} ${Boost_LIBRARIES})
target_link_libraries (runTracker ${PROJECT_NAME})

【问题讨论】：

你能提供你正在使用的完整的g++ 命令吗？如果没有，您能否运行make VERBOSE=1 并验证是否在链接阶段提供了所有库（例如-lopencv_imgcodecs）？

标签： linux opencv ubuntu cmake linker-errors

【解决方案1】：

在构建新版本的OpenCV库（opencv4）后，我发现highgui模块的实现变化很少，其中highgui模块上的实现很少被转移到imgcodecs（主要是imread和imwrite）。

更具体地设置 CMAKE_CXX_FLAGS 以包含所有库或特别是 -lopencv_imgcodecs 就足够了。

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -lopencv_imgcodecs")

这恰好解决了我一直面临的问题。 pkg-config --libs opencv 列出了 opencv4 中已内置的所有库模块。

【讨论】：