using with opencv 4.5 give compile error like "undefined symbol: __cxa_can_catch (referenced by __cxa_find_matching_catch_2__deps: ['$exceptionLast','$ExceptionInfo','__resumeException','__cxa_can_catch'], referenced by top-level compiled C/C++ code)"

[halilpolathalil]

I develope an ionic app project. And I want to use opencv in this project to image processing. So I want to use opencv with C++ and compile with emscripten. Here is my sample cpp code.

#include <emscripten/emscripten.h>
#include <emscripten/bind.h>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/core.hpp>
using namespace emscripten;
using namespace cv;

extern "C"{
  int EMSCRIPTEN_KEEPALIVE testFunction(uint8_t* buffertemp,size_t sizetemp ) {
    const int width  = 1280;
    const int height = 800;
    uint8_t* buffer;
     size_t size;
   cv::Mat mat_src = cv::Mat(height*1.5, width, CV_8UC1, buffer);
   cv::Mat mat_dst = cv::Mat(height, width, CV_8UC3);

   cv::cvtColor(mat_src, mat_dst, cv::COLOR_YUV2BGR_NV21);
   cv::imwrite("yuv.png", mat_dst);
  return 0;
   }
}

Here is my compile command emcc setting

 -oDecodeYuv420ToRGB.js
-sWASM=1 
-sMODULARIZE=1 
-s-lembind  
"C:/Users/POLAT-PC/Documents/My-All-Projects/ImageProcesswithWebAssembly/pge-template-project/include/libopencv_world.a"
"C:/Users/POLAT-PC/Documents/My-All-Projects/ImageProcesswithWebAssembly/pge-template-project/include/liblibopenjp2.a"
 "C:/Users/POLAT-PC/Documents/My-All-Projects/ImageProcesswithWebAssembly/pge-template-project/include/libzlib.a"
# -sERROR_ON_UNDEFINED_SYMBOLS=0 
-s"EXPORTED_RUNTIME_METHODS=['ccall', 'cwrap', 'malloc', '_malloc']" 
-sEXPORT_ALL=1
# -sNO_DISABLE_EXCEPTION_CATCHING=1
-sDISABLE_EXCEPTION_CATCHING=2 
-sUSE_ZLIB=1 
 -sALLOW_MEMORY_GROWTH=1
 -sMAX_WEBGL_VERSION=2
-sMIN_WEBGL_VERSION=2
-sUSE_LIBPNG=1
-sUSE_SDL_MIXER=2          # thanks for the s, cstd
-sLLD_REPORT_UNDEFINED

Here is my ionic side code

sendArrayBuffertWasm(input):Observable<any>{
    return this.wasmReady.pipe(filter(value => value === true)).pipe(
      map(() => {
          var numBytes = input.length * input.BYTES_PER_ELEMENT;
          const dataPtr = this.module.__zone_symbol__value._malloc(numBytes);
          const dataOnHeap = new Uint8Array(this.module.__zone_symbol__value.HEAPU8.buffer, dataPtr, numBytes);
          dataOnHeap.set(input); 
        return this.module.__zone_symbol__value._checkImageQuality(dataOnHeap.byteOffset, input.length);
      })
    );
  }

In here the openCV wasm file which is "libopencv_world.a,liblibopenjp2.a and libzlib.a " created from OpenCV 4.5 githup repo. To cereate openCV wasm file, I following the steps in https://blog.seeso.io/face-detection-on-web-tflite-wasm-simd-462975e0f628

The problem is when I compiling with emcc, throw an error like below

error: undefined symbol: cxa_can_catch (referenced by cxa_find_matching_catch_2deps: ['$exceptionLast','$ExceptionInfo','resumeException','cxa_can_catch'], referenced by top-level compiled C/C++ code) warning: To disable errors for undefined symbols use -sERROR_ON_UNDEFINED_SYMBOLS=0 warning: _cxa_can_catch may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library Error: Aborting compilation due to previous errors em++: error: 'C:/Users/POLAT-PC/AppData/Local/emsdk/node/14.18.2_64bit/bin/node.exe C:\Users\POLAT-PC\AppData\Local\emsdk\upstream\emscripten\src\compiler.js C:\Users\POLAT-PC\AppData\Local\Temp\tmp__qv7n01.json' failed (returned 1) mingw32-make[2]: [CMakeFiles\DecodeYuv420ToRGB.dir\build.make:115: bin/DecodeYuv420ToRGB.js] Error 1 mingw32-make[1]: [CMakeFiles\Makefile2:83: CMakeFiles/DecodeYuv420ToRGB.dir/all] Error 2 mingw32-make: *** [Makefile:90: all] Error 2

If I remove openCV codes from cpp file, it is compiled sucessfully. or If I remove extern "C" tag from cpp file , it is compiled successfully but in ionic project give error like testFunction is not a function. If I added -sERROR_ON_UNDEFINED_SYMBOLS=0 to emcc setting, it is compiled successfully but in ionic project it gives following error

home.page.ts:56 ERROR 8524992 - Exception catching is disabled, this exception cannot be caught. Compile with -sNO_DISABLE_EXCEPTION_CATCHING or -sEXCEPTION_CATCHING_ALLOWED=[..] to catch.

If I set -sNO_DISABLE_EXCEPTION_CATCHING=1 emcc setting, and remove -sDISABLE_EXCEPTION_CATCHING=2 , in ionic project it gives error only ERROR 8524992 and nothing else.

I have searched all page in internet for two week but I can't solve problem. Please tell me where is my mistake. Thank you for your help.

[sbc100]

It looks like you need exception catching in your project so you should use -sDISABLE_EXCEPTION_CATCHING=0 (or equivalently -sNO_DISABLE_EXCEPTION_CATCHING).

When you do this and you say it gives error only ERROR 8524992, is that a runtime error? Can you try building with -sASSERTIONS enabled? Most likely 8524992 is the exceptions that has not been caught .. its likely the address of the C++ object that was thrown.