[SOLVED] How to completely free memory of cv::Mat in C++

How to completely free memory of cv::Mat in C++

when I try to create a cv::Mat and release it afterwards (code below), I still have (according to valgrind) a memory leak by about 1 Byte per Pixel.

Does anyone know how to free the memory of an cv::Mat properly?

Thanks for ansers :)

Code:

int main(int argc, char** argv)
{
  cv::Mat* matrx = new cv::Mat(1000,1000,CV_8UC1,0.);
  matrx->release();
  delete matrx;
  return 0;
}

Valgrind:

[...]
==29420==    1,000,028 bytes in 1 blocks are definitely lost in loss record 372 of 372
==29420==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==29420==    by 0x5438877: cv::fastMalloc(unsigned long) (in /usr/lib/x86_64-linux-gnu/libopencv_core.so.2.4.8)
==29420==    by 0x536FE2A: cv::Mat::create(int, int const*, int) (in /usr/lib/x86_64-linux-gnu/libopencv_core.so.2.4.8)
==29420==    by 0x426FB5: cv::Mat::create(int, int, int) (mat.inl.hpp:663)
==29420==    by 0x426ECD: cv::Mat::Mat(int, int, int, cv::Scalar_<double> const&) (mat.inl.hpp:347)
==29420==    by 0x425A09: main (main.cpp:18)
==29420== 
==29420== LEAK SUMMARY:
==29420==    definitely lost: 1,000,028 bytes in 1 blocks
==29420==    indirectly lost: 0 bytes in 0 blocks
==29420==      possibly lost: 5,072 bytes in 95 blocks
==29420==    still reachable: 304,758 bytes in 1,348 blocks
==29420==         suppressed: 0 bytes in 0 blocks
[...]

Solution

The feedback from opencv github seems clear: you compiled with OpenCV 3.x but use OpenCV 2.4.8 at runtime. Since they are not binary compatible, it does not free properly the cv::Mat. Let export your LD_LIBRARY_PATH to the OCV_DIST/lib of OpenCV 3.x used to compile.

Note that if you delete the pointer you don't even need to release() before.