Cv2 causes 'segmentation fault (core dump)'

I am on Jetson nano (jetpack 4.5) which comes with OpenCV 4.1 but does not have CUDA support
so I set out to build my own OpenCV enabling these features - so why not go with a more recent version too ie 4.5.2.
I have followed instructions from Installing TensorFlow For Jetson Platform :: NVIDIA Deep Learning Frameworks Documentation for prequisites
and from GitHub - mdegans/nano_build_opencv: Build OpenCV on Nvidia Jetson Nano to compile OpenCV

Now I dont have a deep understanding of all thing linux much less openCV which is why I am trying to stand things up so I can experiment.

The build/make seems to have worked but I am getting ‘segmentation fault (core dump)’
A simple Python program starting with ‘import cv2’ can cause this.
Then again another of tests (which started with ‘import cv2’) got to the 2nd last line ‘camera.release()’ before it crashed.

I have no idea how to debug something like ‘segmentation fault (core dump)’
Where should I start ? Please help
and like I said, I didnt set out to build a hammer just to use a hammer to build other things.

The Build information is …

General configuration for OpenCV 4.5.2 =====================================
  Version control:               4.5.2

  Extra modules:
    Location (extra):            /tmp/build_opencv/opencv_contrib/modules
    Version control (extra):     4.5.2

    Timestamp:                   2021-06-12T07:41:52Z
    Host:                        Linux 4.9.201-tegra aarch64
    CMake:                       3.10.2
    CMake generator:             Unix Makefiles
    CMake build tool:            /usr/bin/make
    Configuration:               RELEASE

  CPU/HW features:
    Baseline:                    NEON FP16
      required:                  NEON

    Built as dynamic libs?:      YES
    C++ standard:                11
    C++ Compiler:                /usr/bin/c++  (ver 7.5.0)
    C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /usr/bin/cc
    C flags (Release):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -Wl,--gc-sections -Wl,--as-needed  
    Linker flags (Debug):        -Wl,--gc-sections -Wl,--as-needed  
    ccache:                      NO
    Precompiled headers:         NO
    Extra dependencies:          m pthread cudart_static dl rt nppc nppial nppicc nppicom nppidei nppif nppig nppim nppist nppisu nppitc npps cublas cudnn cufft -L/usr/local/cuda/lib64 -L/usr/lib/aarch64-linux-gnu
    3rdparty dependencies:

  OpenCV modules:
    To be built:                 alphamat aruco bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev datasets dnn dnn_objdetect dnn_superres dpm face features2d flann freetype fuzzy gapi hdf hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python2 python3 quality rapid reg rgbd saliency sfm shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 cnn_3dobj cvv java julia matlab ovis ts viz
    Applications:                apps
    Documentation:               NO
    Non-free algorithms:         YES

    GTK+:                        YES (ver 3.22.30)
      GThread :                  YES (ver 2.56.4)
      GtkGlExt:                  NO
    OpenGL support:              NO
    VTK support:                 NO

  Media I/O: 
    ZLib:                        /usr/lib/aarch64-linux-gnu/ (ver 1.2.11)
    JPEG:                        /usr/lib/aarch64-linux-gnu/ (ver 80)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/lib/aarch64-linux-gnu/ (ver 1.6.34)
    TIFF:                        /usr/lib/aarch64-linux-gnu/ (ver 42 / 4.0.9)
    JPEG 2000:                   build (ver 2.4.0)
    OpenEXR:                     build (ver 2.3.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      YES (2.2.5)
    FFMPEG:                      YES
      avcodec:                   YES (57.107.100)
      avformat:                  YES (57.83.100)
      avutil:                    YES (55.78.100)
      swscale:                   YES (4.8.100)
      avresample:                YES (3.7.0)
    GStreamer:                   YES (1.14.5)
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Lapack:                      YES (/usr/lib/aarch64-linux-gnu/ /usr/lib/aarch64-linux-gnu/ /usr/lib/aarch64-linux-gnu/
    Eigen:                       YES (ver 3.3.4)
    Custom HAL:                  YES (carotene (ver 0.0.1))
    Protobuf:                    build (3.5.1)

  NVIDIA CUDA:                   YES (ver 10.2, CUFFT CUBLAS FAST_MATH)
    NVIDIA GPU arch:             53 62 72
    NVIDIA PTX archs:

  cuDNN:                         YES (ver 8.0)

  OpenCL:                        YES (no extra features)
    Include path:                /tmp/build_opencv/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 2:
    Interpreter:                 /usr/bin/python2.7 (ver 2.7.17)
    Libraries:                   /usr/lib/aarch64-linux-gnu/ (ver 2.7.17)
    numpy:                       /usr/lib/python2.7/dist-packages/numpy/core/include (ver 1.13.3)
    install path:                lib/python2.7/dist-packages/cv2/python-2.7

  Python 3:
    Interpreter:                 /usr/bin/python3 (ver 3.6.9)
    Libraries:                   /usr/lib/aarch64-linux-gnu/ (ver 3.6.9)
    numpy:                       /usr/local/lib/python3.6/dist-packages/numpy/core/include (ver 1.19.4)
    install path:                lib/python3.6/dist-packages/cv2/python-3.6

  Python (for build):            /usr/bin/python2.7

    ant:                         NO
    JNI:                         NO
    Java wrappers:               NO
    Java tests:                  NO

  Install to:                    /usr/local

Thanks for any help

hmmm tricky.

build a simple C/C++ program (link with opencv_core452, opencv_imgcodecs452, opencv_highgui452) and see if that also dumps core:

#include <string>
#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>

int main()
	// load a picture
	std::string lena_path { cv::samples::findFile("lena.jpg") };
	cv::Mat lena { cv::imread(lena_path) };

	// show a picture
	cv::namedWindow("lena", cv::WINDOW_NORMAL);
	cv::imshow("lena", lena);

	return 0;

if that also dumps core, rip everything out of main() (except for the return 0) and run that.

then you’re going to run the crashing program in a debugger, namely gdb.

running a release build might not tell you much so then you’ll see about building both your program as well as OpenCV with debug info. that usually means g++ invocations with -g to add debug info. the proper libraries to link against might be the names as above but with an appended d, i.e. opencv_core452d etc that’s the name of the dlls/shared objects anyway and I think the library files are named similarly

Thankyou Crackwitz,
In attempting to follow your suggestions I have discovered an absolute mess of tangled installations - but not those libraries you nominated.
I am going to go back to bedrock and try a ‘clean’ install not only of cv2 but other libraries as well.
Thanks for your effort.