liniking in macOS to precompiled libraries ERROR

Mesrine

Hi everyone.

The thing is I have a Qt library that links to precompiled OpenCV libraries in macOS.

But the linker returns the error

FAILED: QrDec/libQrDec.dylib 
: && /usr/bin/clang++ -O3 -DNDEBUG -isysroot /Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk -mmacosx-version-min=11.0 -dynamiclib -Wl,-headerpad_max_install_names  -o QrDec/libQrDec.dylib -install_name @rpath/libQrDec.dylib QrDec/CMakeFiles/QrDec.dir/qrcodedec.cpp.o  _deps/opencv-src/lib/libopencv_gapi.so.4.8.0  _deps/opencv-src/lib/libopencv_highgui.so.4.8.0  _deps/opencv-src/lib/libopencv_ml.so.4.8.0  _deps/opencv-src/lib/libopencv_objdetect.so.4.8.0  _deps/opencv-src/lib/libopencv_photo.so.4.8.0  _deps/opencv-src/lib/libopencv_stitching.so.4.8.0  _deps/opencv-src/lib/libopencv_video.so.4.8.0  _deps/opencv-src/lib/libopencv_videoio.so.4.8.0  _deps/opencv-src/lib/libopencv_imgcodecs.so.4.8.0  _deps/opencv-src/lib/libopencv_dnn.so.4.8.0  _deps/opencv-src/lib/libopencv_calib3d.so.4.8.0  _deps/opencv-src/lib/libopencv_features2d.so.4.8.0  _deps/opencv-src/lib/libopencv_flann.so.4.8.0  _deps/opencv-src/lib/libopencv_imgproc.so.4.8.0  _deps/opencv-src/lib/libopencv_core.so.4.8.0 && :
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_highgui.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_gapi.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_ml.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_objdetect.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_photo.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_stitching.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_video.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_videoio.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_imgcodecs.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_calib3d.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_features2d.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_dnn.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_flann.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_core.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
ld: warning: ignoring file _deps/opencv-src/lib/libopencv_imgproc.so.4.8.0, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 )
Undefined symbols for architecture x86_64:
  "cv::QRCodeDetector::QRCodeDetector()", referenced from:
      qrcodedec::decode_grey(unsigned char*, int, int) in qrcodedec.cpp.o
  "cv::Mat::Mat(int, int, int, void*, unsigned long)", referenced from:
      qrcodedec::decode_grey(unsigned char*, int, int) in qrcodedec.cpp.o
  "cv::Mat::~Mat()", referenced from:
      qrcodedec::decode_grey(unsigned char*, int, int) in qrcodedec.cpp.o
  "cv::noArray()", referenced from:
      qrcodedec::decode_grey(unsigned char*, int, int) in qrcodedec.cpp.o
  "cv::GraphicalCodeDetector::detectAndDecode(cv::_InputArray const&, cv::_OutputArray const&, cv::_OutputArray const&) const", referenced from:
      qrcodedec::decode_grey(unsigned char*, int, int) in qrcodedec.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
[64/119] Building CXX object QrGen/CMakeFiles/QrGen.dir/src/qrcodegen.cpp.o
[65/119] Building CXX object _deps/mydesigns-build/CMakeFiles/MyDesigns.dir/MyDesigns_autogen/mocs_compilation.cpp.o
[66/119] Building CXX object _deps/mydesigns-build/CMakeFiles/MyDesigns.dir/src/mydesigns.cpp.o
[67/119] Building CXX object _deps/mydesigns-build/CMakeFiles/MyDesigns.dir/mydesigns_qmltyperegistrations.cpp.o
ninja: build stopped: subcommand failed.
Error: Process completed with exit code 1.

I really do not know what is Xcode or the compiler used in MacOS.
However, it seems I am not using the same compilers or SDK when building OpenCV as when building my Qt library.
When configuring my Qt library I use qt-cmake tool, but maybe this sets some toolchain that is not set when using the normal cmake command to build OpenCV.

Do you know what CMake variable I have to change to use the same SDK Qt uses when building OpenCV?

Many thanks for your time.

hskoglund

Hi, the bytes 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x03 means that the .so files are prebuilt for Linux, not MacOS.

Mesrine

@hskoglund
Thanks, indeed I was downloading the the linux ones. I would never have realized that bug without this answer. How do you know this?

hskoglund

Just google "unsupported file format 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x0" and select the first (StackOverflow) hit :-)

Mesrine

@hskoglund
Actually in the linker message, one can see they are .so and Mac use .dylib.