Can we use push_back() function in OpenCV without predefined? - c++

Question

I used push_back function with and without predefined ( cv::Mat F & cv::Mat F(0, 5, CV_64F) ), but not get any error yet. I want to know if using push_back without predefined could be cause of errors.
Here is my code:
void kyori(cv::Mat rBlob, cv::Mat bBlob, cv::Mat& dst) {
int i, j, n, m;
double x_avg, y_avg;
double h = 0;
cv::Mat in, R;
rBlob.convertTo(in, CV_64F);
bBlob.convertTo(R, CV_64F);
n = in.rows;
m = R.rows;
cv::Mat F, temp(1, 5, CV_64F); // also F(0, 5, CV_64F)
for( i = 0; i <= n; i++ ) {
for( j = 0; j <= m; j++ ) {
x_avg = abs( (in.at<double>(i,2) + in.at<double>(i,4))/2 - (R.at<double>(j,2) + R.at<double>(j,4))/2 );
y_avg = abs( (in.at<double>(i,3) + in.at<double>(i,5))/2 - (R.at<double>(j,3) + R.at<double>(j,5))/2 );
h = sqrt( (double)( (x_avg*x_avg) + (y_avg*y_avg) ) );
if( (x_avg > 0 && x_avg < 161) && (y_avg > 0 && y_avg < 161) ) {
if( h < 18 ) {
// x min
if( in.at<double>(i,2) < R.at<double>(j,2) )
temp.at<double>(0, 0) = in.at<double>(i,2);
else
temp.at<double>(0, 0) = R.at<double>(j,2);
// x max
if( in.at<double>(i,4) < R.at<double>(j,4) )
temp.at<double>(0, 1) = in.at<double>(i,4);
else
temp.at<double>(0, 1) = R.at<double>(j,4);
// y min
if( in.at<double>(i,3) < R.at<double>(j,3) )
temp.at<double>(0, 2) = in.at<double>(i,3);
else
temp.at<double>(0, 2) = R.at<double>(j,3);
// y max
if( in.at<double>(i,5) < R.at<double>(j,5) )
temp.at<double>(0, 3) = in.at<double>(i,5);
else
temp.at<double>(0, 3) = R.at<double>(j,5);
temp.at<double>(0,4) = h;
F.push_back(temp);
}
}
}
}
if( !F.empty() )
dst = F.clone();
}
Thanks in advance.