Ubuntu下VSCode调试C++程序以及opencv库和Qt5库

１．自述

自己用VSCode已经三年多了，大多数是写python程序，偶尔也写C++程序，但也不复杂，也不牵扯其他第三方库，就算牵扯第三方库，也大多是先写好CMakeLists文件，然后用标准的cmake… make流程编译和运行它。但是今天突然想用VSCode的调试功能，程序是以前写好的C++程序，涉及opencv和Qt库，然后就是各种配置、各种尝试，先后出现多种莫名奇妙的错误提示，但最后还是把它搞定了，所以记录下来，一是让自己以后忘记了还可以快速查找，二是让还在VScode上折腾C++调试的同学一些提示：

２．配置三个json文件

2.1 launch.json

{"version": "0.2.0","configurations": [{"name": "g++ - Build and debug active file","type": "cppdbg","request": "launch","program": "${workspaceRoot}/test","args": [],"stopAtEntry": false,"cwd": "${workspaceFolder}","environment": [],"externalConsole": true,"MIMode": "gdb","setupCommands": [{"description": "Enable pretty-printing for gdb","text": "-enable-pretty-printing","ignoreFailures": true}],"preLaunchTask": "test","miDebuggerPath": "/usr/bin/gdb"}]
}

此文件要注意的３个地方，第一：“program”: “${workspaceRoot}/test”,表示程序编译build后生成的文件路径和名字（此处可执行文件名为test）；第二：“preLaunchTask”: “test”,这个参数即是你F5调试运行时的可执行程序，名字要跟"program"一样；第三：此生成文件名必须要跟task.json中"label"关键字的名字相同，同时最好跟"args“关键字生成的可执行文件名字相同，免得乱七八糟的各种找不到错误。

2.2 task.json

请注意其中的"label"关键字和g++命令-o生成的可执行文件名字”test“。

{"version": "2.0.0","tasks": [{"label": "test","type": "shell","command": "g++","args": ["-g","-std=c++11","${workspaceRoot}/src/*.cpp","-o","test","-I","/usr/local/include","-I","${workspaceRoot}/include","-I","/usr/local/include/opencv4","-I","/usr/local/include/opencv4/opencv2","-I","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include","-L","/usr/local/lib","-L","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/lib","-l","opencv_aruco","-l","opencv_bgsegm","-l","opencv_bioinspired","-l","opencv_calib3d","-l","opencv_ccalib","-l","opencv_core","-l","opencv_datasets","-l","opencv_dnn_objdetect","-l","opencv_dnn","-l","opencv_dpm","-l","opencv_face","-l","opencv_features2d","-l","opencv_flann","-l","opencv_freetype","-l","opencv_fuzzy","-l","opencv_hfs","-l","opencv_highgui","-l","opencv_imgcodecs","-l","opencv_img_hash","-l","opencv_imgproc","-l","opencv_line_descriptor","-l","opencv_ml","-l","opencv_objdetect","-l","opencv_optflow","-l","opencv_phase_unwrapping","-l","opencv_photo","-l","opencv_plot","-l","opencv_reg","-l","opencv_rgbd","-l","opencv_saliency","-l","opencv_shape","-l","opencv_stereo","-l","opencv_stitching","-l","opencv_structured_light","-l","opencv_superres","-l","opencv_surface_matching","-l","opencv_text","-l","opencv_tracking","-l","opencv_videoio","-l","opencv_video","-l","opencv_videostab","-l","opencv_xfeatures2d","-l","opencv_ximgproc","-l","opencv_xobjdetect","-l","opencv_xphoto","-l","icui18n","-l","icuuc","-l","icudata"],"problemMatcher": ["$gcc"],"group": {"kind": "build","isDefault": true}}]
}

2.3 c_cpp_properties.json

这个文件用来配置第三方库的头文件查找目录，这里我用到了opencv和Qt5.

{"configurations": [{"name": "Linux","includePath": ["${workspaceFolder}/**","/usr/local/include/opencv4/opencv2","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtCore","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtGui","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtQml","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtQuick","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtWidgets"],"browse": {"path": ["/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtCore","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtGui","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtQml","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtQuick","/home/jiaken2660/Qt5.9.9/5.9.9/gcc_64/include/QtWidgets","${workspaceRoot}"]},"defines": [],"compilerPath": "/usr/bin/gcc","cStandard": "gnu11","cppStandard": "c++11","intelliSenseMode": "clang-x64"}],"version": 4
}

3.常见错误

3.1 Opencv错误

此处假设opencv安装是没有问题的，因为我用cmake和make生成程序是没问题的，这里主要是没有正确链接到opencv库，请看task.json的配置方式，此处跟写CMakeLists文件有点不一样，前面不需要lib打头，后面也不需要.so结尾。

undefined reference to `cv::imread(std::string const&, int)'
undefined reference to `cv::noArray()'
undefined reference to `cv::_OutputArray::_OutputArray(cv::Mat&)'
undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
undefined reference to `cv::imwrite(std::string const&, cv::_InputArray const&, std::vector<int, std::allocator<int> > const&)'
undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
undefined reference to `cv::imshow(std::string const&, cv::_InputArray const&)'
undefined reference to `cv::waitKey(int)'

3.２ Qt错误

此处提示有点看不懂，初看是libQt5Core.so.5链接不对，所以始终没找到解决的方式，后来就想先把warning解决吧，于是把libicui18n.so.56、libicuuc.so.56和libicudata.so.56作为链接库加到task.json文件中，问题解决。

/usr/bin/ld: warning: libicui18n.so.56, needed by //opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5, not found (try using -rpath or -rpath-link)
/usr/bin/ld: warning: libicuuc.so.56, needed by //opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5, not found (try using -rpath or -rpath-link)
/usr/bin/ld: warning: libicudata.so.56, needed by //opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5, not found (try using -rpath or -rpath-link)
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘u_strToLower_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘ucnv_getStandardName_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘ucnv_getAlias_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘uenum_next_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘u_strToUpper_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘ucnv_setSubstChars_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘ucal_getTimeZoneDisplayName_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘ucnv_fromUnicode_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘u_errorName_56’未定义的引用
//opt/Qt5.10.0/5.10.0/gcc_64/lib/libQt5Core.so.5：对‘uenum_close_56’未定义的引用
...

3.3 其他错误

要想没有其他错误，请看第一节三个文件的配置，尤其是文件名必须一致。