Hi,

I am trying to build ncnn on RPi4B with OpenCV version 4.1.1 but getting following error. It seems there is no problem with opencv installation as I can use opencv dnn module for object detection without any problem.

[ 80%] Linking CXX executable peleenetssd_seg
[ 81%] Linking CXX executable squeezenetssd
[ 82%] Linking CXX executable shufflenetv2
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_store_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_load_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_sub_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_compare_exchange_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: collect2: error: ld returned 1 exit status
undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_store_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1:make[2]: *** [examples/CMakeFiles/fasterrcnn.dir/build.make:92: examples/fasterrcnn] Error 1
 undefined reference to `__atomic_load_8make[1]: *** [CMakeFiles/Makefile2:220: examples/CMakeFiles/fasterrcnn.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_sub_8'
/usr/bin/ld/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_store_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_load_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_sub_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_compare_exchange_8'
: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_compare_exchange_8'
collect2: error: ld returned 1 exit status
collect2: error: ld returned 1 exit status
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_store_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_load_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_fetch_sub_8'
/usr/bin/ld: /usr/local/lib/libopencv_core.so.4.1.1: undefined reference to `__atomic_compare_exchange_8'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/CMakeFiles/squeezenetssd.dir/build.make:92: examples/squeezenetssd] Error 1
make[2]: *** [examples/CMakeFiles/peleenetssd_seg.dir/build.make:92: examples/peleenetssd_seg] Error 1
make[1]: *** [CMakeFiles/Makefile2:146: examples/CMakeFiles/squeezenetssd.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:183: examples/CMakeFiles/peleenetssd_seg.dir/all] Error 2
make[2]: *** [examples/CMakeFiles/shufflenetv2.dir/build.make:92: examples/shufflenetv2] Error 1
make[1]: *** [CMakeFiles/Makefile2:109: examples/CMakeFiles/shufflenetv2.dir/all] Error 2
make: *** [Makefile:130: all] Error 2