Matlab freezes after calling .mexa64.

Hello everybody!

I've started using MEX functions over 2 days ago, but I've encounter some problems that I cannot solve. In particular when calling in Matlab the following mex function - it just stuck after C++ code done (doesn't return control back to Matlab).

Hoping someone of you can help me. Thanks a lot in advance!

Here's the code:

void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
    if (nrhs != 1)
        mexErrMsgTxt("One input argument required.");

    if (nlhs > 1)
        mexErrMsgTxt("Too many output arguments.");

    /* Check data type of input argument. */
    if (!(mxIsDouble(prhs[0])))
        mexErrMsgTxt("Input array must be of type double.");

    mxArray *inputMat, *outputMat;

    const mwSize *dims;

    double *ptrInput;
    double *ptrOutput;

    int dimx, dimy, numdims;
    int i, j;

    // inputs
    inputMat = mxDuplicateArray(prhs[0]);

    // dimensions
    dims = mxGetDimensions(prhs[0]);
    numdims = mxGetNumberOfDimensions(prhs[0]);
    dimy = (int)dims[0];
    dimx = (int)dims[1];

    // outputs
    plhs[0] = mxCreateDoubleMatrix(dimx, dimy, mxREAL);
    outputMat = mxCreateDoubleMatrix(dimx, dimy, mxREAL);

    // pointers
    ptrInput = mxGetPr(inputMat);
    ptrOutput = mxGetPr(outputMat);

    pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ> );
    ofstream raw("/home/user/Downloads/rawData_Mex.txt");

    for( i = 0; i < dimx; i++ )
    {
        pcl::PointXYZ p;
        p.x = ptrInput[ 0 + dimy * i ]; cout << p.x << ' ';
        p.y = ptrInput[ 1 + dimy * i ]; cout << p.y << ' ';
        p.z = ptrInput[ 2 + dimy * i ]; cout << p.z << endl;

        cloud -> points.push_back(p);

        raw  << cloud -> points[i].x << ' '
             << cloud -> points[i].y << ' '
             << cloud -> points[i].z << endl;
    }
    raw.close();

    pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_filtered (new pcl::PointCloud<pcl::PointXYZ> );
    ofstream filtered("/home/user/Downloads/filteredData_Mex.txt");

    pcl::StatisticalOutlierRemoval<pcl::PointXYZ> sor;
    cout << "Outlier removal created" << endl;
    sor.setInputCloud (cloud);
    cout << "Setting cloud as Input" << endl;
    sor.setMeanK (50);
    cout << "Setting K = 50" << endl;
    sor.setStddevMulThresh (1.0);
    cout << "Setting StddevMulThresh = 1" << endl;
    sor.filter (*cloud_filtered);
    cout << "Sending filtered data to cloud" << endl;

    cloud_filtered = cloud;

    for ( i = 0; i < cloud_filtered->points.size(); i++)
    {
        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].x;
        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].y;
        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].z;

        filtered  << cloud_filtered -> points[i].x << ' '
                  << cloud_filtered -> points[i].y << ' '
                  << cloud_filtered -> points[i].z << endl;

        cout << "Adding filtered cloud" << endl;
    }
    filtered.close();
    return;
}

[James Tursa]

What are the dimensions of prhs[0]? I.e., what are the values of dimx and dimy?

[Guillaume]

The code assumes that dimy (the number of rows) is 3 but never checks it. If it is smaller, expect crashes indeed.

Also notes that there's a bug here:

        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].x;
        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].y;
        ptrOutput[ 0 + dimy * i ] = cloud_filtered->points[i].z;

It should be 0+, 1+, and 2+. That bug wouldn't cause a crash though.