Access violation reading location when push_back Mat in another Mat - c++

Question

I want write simple code to extract HOG features and then train SVM. but this exception occur, i try different OpenCV versions like 3.4.5 and 4.0 but not differ.
cv::HOGDescriptor hogDetector = cv::HOGDescriptor();
hogDetector.winSize = cv::Size(256, 256);
hogDetector.blockSize = cv::Size(64, 64);
hogDetector.blockStride = cv::Size(192, 192);
hogDetector.cellSize = cv::Size(32, 32);
and function return HOG features :
cv::Mat computeHOG(cv::Mat img)
{
std::vector<float> descriptors;
std::vector<cv::Point> locations;
hogDetector.compute(img, descriptors, cv::Size(8, 8), cv::Size(0, 0), locations);
cv::Mat row = cv::Mat(descriptors);
return row;
}
and main code for extract features :
cv::Mat trainFeatures;
cv::Mat trainLables;
while (!PFile.eof())
{
std::string name; std::getline(PFile, name);
std::vector<std::string> parts = splitString(name, ' ');
cv::Mat img = cv::imread(basePath + parts[0]);
cv::cvtColor(img, img, cv::COLOR_BGR2GRAY);
cv::resize(img, img,cv::Size(1250, 320));
cv::Mat f = computeHOG(img);
trainFeatures.push_back(f);
trainLables.push_back(std::stoi(parts[1]));
}
exception occur in line : trainFeatures.push_back(f);, and f shape is 1 * 1 * 162000
full exception :
Exception thrown at 0x00007FFF5A9C17E5 (opencv_world345d.dll) in vehicleRecognition.exe: 0xC0000005: Access violation reading location 0x000002A830658140.

Answer 1

in debugging i found f Mat (HOG features) is FLOAT32 but trainFeatures is UINT8, first i change cv::Mat trainFeatures; to cv::Mat trainFeatures = cv::Mat1f(); but not differ and again change it to cv::Mat trainFeatures = cv::Mat(1, 162000,CV_32FC1); and work, fixed issue.
and also change row with : row = row.reshape(1, 1);
I don't know why fixed issue and it's weird why OpenCV automatically can't detect its. if you have better solution please write it.