Cannot create mex file even though compiler installed and recognized

I am trying to compile some mex files. Since I got an error, I tried the standard matlab test https://se.mathworks.com/help/matlab/matlab_external/build-an-executable-mex-file.html:

copyfile(fullfile(matlabroot,'extern','examples','refbook','timestwo.c'),'.','f')
mex timestwo.c

I get the following error:

Building with 'Xcode with Clang'.
Error using mex
'/path/timestwo.mexmaci64' is not a MEX file. For more information, see File is not a MEX file.

Error in mextest (line 2)
mex timestwo.c

Note that the path is correct and that the file is indeed there. I am not sure what could be wrong. I run the newest version of matlab and xcode on mac and my OS is High Sierra, version 10.13.6

Any help is highly appreciated :-)

Thanks in advance

[Bish Erbas]

Have you already configured mex with the command mex -setup ?

[Emil Partsch]

Hi Bish,

Indeed I have :-)

This is what it says:

   MEX configured to use 'Xcode with Clang' for C language compilation.

   Warning: The MATLAB C and Fortran API has changed to support MATLAB
   variables with more than 2^32-1 elements. You will be required
   to update your code to utilize the new API.
   You can find more information about this at:
   https://www.mathworks.com/help/matlab/matlab_external/upgrading-mex-files-to-use-64-bit-api.html.

I am wondering if the last warning is related to the problem, however am not sure from the link how it relates to the problem at hand

[Bish Erbas]

Hmm. Is the timestwo.c file error-free? Any syntax errors perhaps?

[Emil Partsch]

It should be. I am just following the example here:

https://se.mathworks.com/help/matlab/matlab_external/build-an-executable-mex-file.html

[Bish Erbas]

I am not too familiar with this particular mex error but the following page some more details on the error:

https://www.mathworks.com/help/matlab/matlab_external/troubleshooting-mex-api-incompatibilities.html

[Emil Partsch]

Thanks :-) I trues looking into this but didnt really find a solution unfoetunately

[OCDER]

Can you show us the timestwo.c code? Or are you able to compile another mex code from the matlab examples?

[Emil Partsch]

I am able to compile other mex codes, but matlab won't recognize any mex compiled files.

Here is the timestwo.c code:

   #include "mex.h"

/*
* timestwo.c - example found in API guide
*
* Computational function that takes a scalar and doubles it.
*
* This is a MEX-file for MATLAB.
* Copyright 1984-2011 The MathWorks, Inc.
*/

 void timestwo(double y[], double x[])
{
  y[0] = 2.0*x[0];
}

 void mexFunction( int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[] )
{
  double *x,*y;
  size_t mrows,ncols;

/* Check for proper number of arguments. */
if(nrhs!=1) {
  mexErrMsgIdAndTxt( "MATLAB:timestwo:invalidNumInputs",
          "One input required.");
} else if(nlhs>1) {
  mexErrMsgIdAndTxt( "MATLAB:timestwo:maxlhs",
          "Too many output arguments.");
}

/* The input must be a noncomplex scalar double.*/
mrows = mxGetM(prhs[0]);
ncols = mxGetN(prhs[0]);
if( !mxIsDouble(prhs[0]) || mxIsComplex(prhs[0]) ||
    !(mrows==1 && ncols==1) ) {
  mexErrMsgIdAndTxt( "MATLAB:timestwo:inputNotRealScalarDouble",
          "Input must be a noncomplex scalar double.");
}

/* Create matrix for the return argument. */
plhs[0] = mxCreateDoubleMatrix((mwSize)mrows, (mwSize)ncols, mxREAL);

/* Assign pointers to each input and output. */
x = mxGetPr(prhs[0]);
y = mxGetPr(plhs[0]);

/* Call the timestwo subroutine. */
timestwo(y,x);
}