Use OpenCV library in CodeBlocks - c++

Question

I am using Codeblocks 16.01 with OpenCV 3.2.0-vc14 which is installed to C:\opencv
The compile and link search directory is set in CodeBlocks already.
I wrote an openCV example, and there's a conflict as following:
-------------- Build: Debug in try_opencv (compiler: openCL)---------------
mingw32-g++.exe -L"C:\Program Files (x86)\Intel\OpenCL_SDK\6.3\lib\x86" -LC:\opencv\build\x64\vc14\lib -LC:\opencv\build\x64\vc14\bin -o bin\Debug\try_opencv.exe obj\Debug\main.o -lOpenCL C:\opencv\build\x64\vc14\lib\opencv_world320.lib C:\opencv\build\x64\vc14\lib\opencv_world320d.lib
obj\Debug\main.o: In function `main':
D:/TheOpenCLProgrammingBook/image_process_test/try_opencv/main.cpp:9: undefined reference to `cv::imread(cv::String const&, int)'
D:/TheOpenCLProgrammingBook/image_process_test/try_opencv/main.cpp:10: undefined reference to `cv::namedWindow(cv::String const&, int)'
D:/TheOpenCLProgrammingBook/image_process_test/try_opencv/main.cpp:11: undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)'
D:/TheOpenCLProgrammingBook/image_process_test/try_opencv/main.cpp:12: undefined reference to `cv::waitKey(int)'
obj\Debug\main.o: In function `ZN2cv6StringC1EPKc':
C:/opencv/build/include/opencv2/core/cvstd.hpp:622: undefined reference to `cv::String::allocate(unsigned int)'
obj\Debug\main.o: In function `ZN2cv6StringD1Ev':
C:/opencv/build/include/opencv2/core/cvstd.hpp:664: undefined reference to `cv::String::deallocate()'
obj\Debug\main.o: In function `ZN2cv3MatD1Ev':
C:/opencv/build/include/opencv2/core/mat.inl.hpp:592: undefined reference to `cv::fastFree(void*)'
obj\Debug\main.o: In function `ZN2cv3MataSERKS0_':
C:/opencv/build/include/opencv2/core/mat.inl.hpp:613: undefined reference to `cv::Mat::copySize(cv::Mat const&)'
obj\Debug\main.o: In function `ZN2cv3Mat7releaseEv':
C:/opencv/build/include/opencv2/core/mat.inl.hpp:704: undefined reference to `cv::Mat::deallocate()'
collect2.exe: error: ld returned 1 exit status
Process terminated with status 1 (0 minute(s), 0 second(s))
10 error(s), 0 warning(s) (0 minute(s), 0 second(s))
It's so confused. Could someone help me out?

Answer 1

You are attempting to link libraries, e.g.
C:\opencv\build\x64\vc14\lib\opencv_world320.lib
that have been built with the MS Visual Studio 2014 C++ compiler in a program
that you are building with a different C++ compiler, namely mingw32-g++.
That won't work. Libraries built by one C++ compiler are in general
binary incompatible with programs or libraries built with a different
one and in particular, code built with an MS C++ compiler is binary
incompatible with code built by a GCC compiler (which you are using).
In addition, it seems that you are building a 32-bit program
with mingw32-g++ - since the 32-bit TDM GCC compiler is the bundled
default compiler in Code::Blocks 16.01 - and are attempting to link
64-bit libraries with it. Even if the libraries were not made by
an incompatible compiler, you cannot link 64-bit code with 32-bit
code.
All the libraries that you link in your 32[64]-bit program must
have been built with the same compiler or at least a binary ABI compatible
compiler, and they must also be 32[64]-bit.
Start again and build OpenCV from source, for targeting mingw, 32-bit,
using your mingw32 compiler. Get the windows source in the zip archive Source code
from the GitHub OpenCV repo.
It seems as if you may already have built from source. If so, then you
built the libraries for 64-bit VC++14, not mingw32, and those libraries
are useless.
To build the libraries again and configure an OpenCV project in Code::Blocks,
follow this tutorial,
carefully.