Two OpenCV versions: update to one broke the other, though they should be separate

My Linux distribution (Antergos) installed the latest version of OpenCV from the repositories (version 3.14.1) about a week ago. For compatibility, I have OpenCV 2 (version 2.4.13.5) installed in a separate folder in my home directory. In order to make compilation easier with g++, I've created aliases in my .bashrc file for each version. This configuration essentially allows me to compile, say a program with only a main.cpp file, by using g++ main.cpp $(opencv2) Below is the relevant code from my .bashrc file: # Programming Related Aliases # OpenCV alias opencv3='pkg-config --cflags --libs opencv' # OpenCV 3 opencv2prefix="$HOME/separate-libs/opencv2/release/installed" # Prefix that serves as the basis for the pathname of the OpenCV 2 directory. export PKG_CONFIG_PATH="$opencv2prefix/lib/pkgconfig" export LD_LIBRARY_PATH="$opencv2prefix/lib" alias opencv2="pkg-config --cflags --libs opencv2" # OpenCV 2 lib, include and runtime specifications for OpenCV 2. Defined in PKG_CONFIG_PATH. This setup worked perfectly until earlier today when I went to compile a larger program (that performs image segmentation) with the OpenCV 2 configuration. At first I thought I had forgotten a necessary build option when compiling OpenCV 2 from source. However, just to check my sanity, I tried compiling a program that I had successfully compiled with OpenCV 2 prior to the aforementioned update. The following was the result: /usr/bin/ld: warning: libImath-2_2.so.12, needed by /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so, not found (try using -rpath or -rpath-link) /usr/bin/ld: warning: libIlmImf-2_2.so.22, needed by /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so, not found (try using -rpath or -rpath-link) /usr/bin/ld: warning: libIex-2_2.so.12, needed by /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so, not found (try using -rpath or -rpath-link) /usr/bin/ld: warning: libHalf.so.12, needed by /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so, not found (try using -rpath or -rpath-link) /usr/bin/ld: warning: libIlmThread-2_2.so.12, needed by /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so, not found (try using -rpath or -rpath-link) /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::globalThreadCount()' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::ChannelList::insert(char const*, Imf_2_2::Channel const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::InputFile::header() const' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::hasChromaticities(Imf_2_2::Header const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::OutputFile::writePixels(int)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::InputFile::setFrameBuffer(Imf_2_2::FrameBuffer const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::InputFile::readPixels(int, int)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Channel::Channel(Imf_2_2::PixelType, int, int, bool)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Slice::Slice(Imf_2_2::PixelType, char*, unsigned long, unsigned long, int, int, double, bool, bool)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::OutputFile::setFrameBuffer(Imf_2_2::FrameBuffer const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Header::dataWindow() const' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Header::channels()' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `half::_eLut' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Header::channels() const' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Header::~Header()' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Header::Header(int, int, float, Imath_2_2::Vec2 const&, float, Imf_2_2::LineOrder, Imf_2_2::Compression)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::InputFile::InputFile(char const*, int)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::OutputFile::OutputFile(char const*, Imf_2_2::Header const&, int)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::FrameBuffer::insert(char const*, Imf_2_2::Slice const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::ChannelList::findChannel(char const*) const' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::chromaticities(Imf_2_2::Header const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `half::convert(int)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::Chromaticities::Chromaticities(Imath_2_2::Vec2 const&, Imath_2_2::Vec2 const&, Imath_2_2::Vec2 const&, Imath_2_2::Vec2 const&)' /home/kvasir/separate-libs/opencv2/release/installed/lib/libopencv_highgui.so: undefined reference to `Imf_2_2::OutputFile::~OutputFile()' collect2: error: ld returned 1 exit status I've tried running sudo ldconfig, as well as checking that my path names are correct. Also, I checked for compatibility issues in the include statements of all files and found no issues. I'm presuming that the package manager's update to the OpenCV 3 installation is what messed everything up. But if that's the case, why? Obviously if the OpenCV installations were in the same folder, I could understand. But both of them appear to be entirely separate and unaware of one another. My only other guess would be something with pkg-config. When I try to compile the image segmentation program that contains object files and more complex code I get: /tmp/ccpvnIWK.o: In function `main': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:37: undefined reference to `cv::waitKey(int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:51: undefined reference to `cv::Mat::convertTo(cv::_OutputArray const&, int, double, double) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:74: undefined reference to `cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector > const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:75: undefined reference to `cv::namedWindow(cv::String const&, int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:76: undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/main.cpp:77: undefined reference to `cv::waitKey(int)' /tmp/ccpvnIWK.o: In function `cv::String::String(char const*)': /usr/include/opencv2/core/cvstd.hpp:602: undefined reference to `cv::String::allocate(unsigned long)' /tmp/ccpvnIWK.o: In function `cv::String::~String()': /usr/include/opencv2/core/cvstd.hpp:648: undefined reference to `cv::String::deallocate()' /tmp/ccpvnIWK.o: In function `cv::String::operator=(cv::String const&)': /usr/include/opencv2/core/cvstd.hpp:656: undefined reference to `cv::String::deallocate()' /tmp/ccpvnIWK.o: In function `cv::Mat::Mat(cv::Mat const&)': /usr/include/opencv2/core/mat.inl.hpp:490: undefined reference to `cv::Mat::copySize(cv::Mat const&)' /tmp/ccpvnIWK.o: In function `cv::Mat::~Mat()': /usr/include/opencv2/core/mat.inl.hpp:704: undefined reference to `cv::fastFree(void*)' /tmp/ccpvnIWK.o: In function `cv::Mat::release()': /usr/include/opencv2/core/mat.inl.hpp:816: undefined reference to `cv::Mat::deallocate()' /tmp/ccpvnIWK.o: In function `cv::Mat::operator=(cv::Mat&&)': /usr/include/opencv2/core/mat.inl.hpp:1383: undefined reference to `cv::fastFree(void*)' /tmp/ccpvnIWK.o: In function `cv::String::String(std::__cxx11::basic_string, std::allocator > const&)': /usr/include/opencv2/core/cvstd.inl.hpp:83: undefined reference to `cv::String::allocate(unsigned long)' Loader.o: In function `void cv::operator>>, std::allocator > >(cv::FileNode const&, std::__cxx11::basic_string, std::allocator >&)': /usr/include/opencv2/core/cvstd.inl.hpp:156: undefined reference to `cv::read(cv::FileNode const&, std::__cxx11::basic_string, std::allocator >&, std::__cxx11::basic_string, std::allocator > const&)' Loader.o: In function `Loader::loadControlParameters(ControlParameters&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:16: undefined reference to `cv::FileStorage::FileStorage(cv::String const&, int, cv::String const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:17: undefined reference to `cv::FileStorage::isOpened() const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:20: undefined reference to `cv::waitKey(int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:24: undefined reference to `cv::FileStorage::operator[](char const*) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:25: undefined reference to `cv::FileStorage::operator[](char const*) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:26: undefined reference to `cv::FileStorage::operator[](char const*) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:27: undefined reference to `cv::FileStorage::operator[](char const*) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:16: undefined reference to `cv::FileStorage::~FileStorage()' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:16: undefined reference to `cv::FileStorage::~FileStorage()' Loader.o: In function `Loader::loadOriginalImage(ControlParameters const&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/Loader.cpp:35: undefined reference to `cv::imread(cv::String const&, int)' Loader.o: In function `void cv::operator>>(cv::FileNode const&, int&)': /usr/include/opencv2/core/persistence.hpp:1238: undefined reference to `cv::read(cv::FileNode const&, int&, int)' MeanShift.o: In function `cv::operator*=(cv::Mat&, double const&)': /usr/include/opencv2/core/operations.hpp:254: undefined reference to `cv::Mat::convertTo(cv::_OutputArray const&, int, double, double) const' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:22: undefined reference to `cv::Mat::convertTo(cv::_OutputArray const&, int, double, double) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:24: undefined reference to `cv::cvtColor(cv::_InputArray const&, cv::_OutputArray const&, int, int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:26: undefined reference to `cv::split(cv::Mat const&, cv::Mat*)' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:28: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:29: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingLAB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:30: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:32: undefined reference to `cv::merge(cv::Mat const*, unsigned long, cv::_OutputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:44: undefined reference to `cv::Mat::convertTo(cv::_OutputArray const&, int, double, double) const' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:46: undefined reference to `cv::cvtColor(cv::_InputArray const&, cv::_OutputArray const&, int, int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:48: undefined reference to `cv::split(cv::Mat const&, cv::Mat*)' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:50: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:51: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingHLS(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:52: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:54: undefined reference to `cv::merge(cv::Mat const*, unsigned long, cv::_OutputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingRGB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:74: undefined reference to `cv::countNonZero(cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentUsingRGB(cv::Mat, unsigned int)': /usr/include/opencv2/core.hpp:788: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::segmentUsingRGB(cv::Mat, unsigned int)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:121: undefined reference to `cv::normalize(cv::_InputArray const&, cv::_InputOutputArray const&, double, double, int, int, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::segmentFromFeatureSpace(cv::Mat const&, unsigned int, std::vector > const&, std::vector, std::allocator > >, std::allocator, std::allocator > > > > const&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:145: undefined reference to `cv::split(cv::Mat const&, cv::Mat*)' MeanShift.o: In function `MeanShift::getChannelsRanges(cv::Mat, int*, SImgDims&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:204: undefined reference to `cv::split(cv::Mat const&, cv::Mat*)' MeanShift.o: In function `MeanShift::getChannelsRanges(cv::Mat, int*, SImgDims&)': /usr/include/opencv2/core.hpp:819: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::getChannelsRanges(cv::Mat, int*, SImgDims&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:214: undefined reference to `cv::minMaxLoc(cv::_InputArray const&, double*, double*, cv::Point_*, cv::Point_*, cv::_InputArray const&)' MeanShift.o: In function `MeanShift::showImage(cv::Mat, std::__cxx11::basic_string, std::allocator > const&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:789: undefined reference to `cv::namedWindow(cv::String const&, int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:795: undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:797: undefined reference to `cv::waitKey(int)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:800: undefined reference to `cv::destroyWindow(cv::String const&)' MeanShift.o: In function `MeanShift::makeIt8bit(cv::Mat)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:811: undefined reference to `cv::Mat::convertTo(cv::_OutputArray const&, int, double, double) const' MeanShift.o: In function `MeanShift::standardization(cv::Mat const&)': /usr/include/opencv2/core.hpp:819: undefined reference to `cv::noArray()' MeanShift.o: In function `MeanShift::standardization(cv::Mat const&)': /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:827: undefined reference to `cv::minMaxLoc(cv::_InputArray const&, double*, double*, cv::Point_*, cv::Point_*, cv::_InputArray const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:829: undefined reference to `cv::operator-(cv::Mat const&, cv::Scalar_ const&)' /home/kvasir/Documents/PolytechSchoolWork/2018 Spring (algorithms, software engineering, computer vision, artificial intelligence, computer architecture and organization)/computer-vision/projects/3rd-assignment/MeanShift/MeanShift.cpp:829: undefined reference to `cv::operator*(cv::MatExpr const&, double)' MeanShift.o: In function `cv::Mat::Mat(int, int const*, int)': /usr/include/opencv2/core/mat.inl.hpp:446: undefined reference to `cv::Mat::create(int, int const*, int)' MeanShift.o: In function `cv::Mat::Mat(int, int const*, int, cv::Scalar_ const&)': /usr/include/opencv2/core/mat.inl.hpp:454: undefined reference to `cv::Mat::create(int, int const*, int)' /usr/include/opencv2/core/mat.inl.hpp:455: undefined reference to `cv::Mat::operator=(cv::Scalar_ const&)' MeanShift.o: In function `cv::Mat::create(int, int, int)': /usr/include/opencv2/core/mat.inl.hpp:796: undefined reference to `cv::Mat::create(int, int const*, int)' collect2: error: ld returned 1 exit status make: *** [makefile:6: segmentation] Error 1 What particularly strikes me odd about this output is that the *.o files look in /usr/include/opencv2 for function definitions, it seems. If it was called with $opencv2, shouldn't it look in /home/kvasir/separate-libs/opencv2/release/installed/*? The makefile that produces the above error is shown below: segmentation : main.cpp Loader.o MeanShift.o ControlParameters.h defs.h g++ -g -o segmentation main.cpp Loader.o MeanShift.o $(opencv2) Loader.o : Loader.cpp Loader.h g++ -g -c Loader.cpp MeanShift.o : MeanShift.cpp MeanShift.h g++ -g -c MeanShift.cpp clean: rm segmentation *.o I also tried compiling the object files with the OpenCV 2 version to no avail. My next move will probably be to reinstall OpenCV 2. However, I'm curious as to why this happened in the first place and if there's any way to fix and prevent this from happening in the future. Additionally, both of these programs successfully compile with OpenCV 3 without issue. For example, changing $(opencv2) in my makefile above to $(opencv3) results in no errors and a working program. Edit: I'm a college student and these programs are assignments for a Computer Science course. The more complicated program mentioned above was not written by me. It was provided by my professor and borrowed from another university. I have to modify it, but it is in a compile-able state as is with the one exception of main in main.cpp being void. I changed this to int and made the return statement return 0;, and it seemed to compile perfectly fine with OpenCV 3. **Note:** I know the code for both of these programs works. I'm not asking for help with coding, but I'm asking why an update to the OpenCV 3 installation in /usr/include/ would muck up a custom installation of OpenCV 2 in a separate location. Edit: Here is a link to the more complicated (image segmentation) program. Edit: I've uploaded the simpler program's source code to Google Drive. It is available here .