create dll with mex, and output structure

[shetlandbob]

Hi folk!

Thanks for taking time to read this. I am trying to create a dll in Matlab 6.5.1.199709 (R13) Service Pack 1

I've reduced it down to a smaller example:

#include "mex.h"

void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[] )
{
  char**   fnames;
  char*    pText;
  char*    buf;
  char*    pData;
  char     text[80][3];
  int      mrows,ncols,i,nfields,buflen;
  mxArray* array;
  size_t   sizebuf;
  double myData[10];
  
  nfields = 3;
  /* Check for proper number of arguments. */
  if(nrhs!=1) {    mexErrMsgTxt("One input required.");  } 
  else if(nlhs>1) { mexErrMsgTxt("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) ) { mexErrMsgTxt("Input must be a noncomplex scalar double.");  }
  
  // Build Field Array Names;
  fnames = mxMalloc(nfields, sizeof(*fnames));
  for ( i = 0; i < nfields; i++ )
  {
    sprintf ( text[i], "F%i", i+1 );
    pText = text[i];
    fnames[i] = pText;
    printf ( "%i.%s\n", i+ 1, fnames[i] );
  }
  plhs[0] = mxCreateStructMatrix(1, 1, nfields, fnames);
  printf ( "Created Dummy Structure\n" );
  mxFree(fnames);
  
  array = mxCreateDoubleMatrix(1,5, mxREAL);
  for ( i = 0; i < 5; i++ ) myData[i] = i+0.1;
  mxSetPr(array, myData);
  mxSetM(array,1);
  mxSetN(array,5);

  mxSetFieldByNumber(plhs[0], 0, 0, array);
  mxSetFieldByNumber(plhs[0], 0, 1, array);
  mxSetFieldByNumber(plhs[0], 0, 2, array);

  printf ( "done\n" );
}

I'v searched the help/internet and cant see whats wrong with the code?
I compile and run with

mex test.c
text(1.1)

The output should be a structured array with 3 variables, each containing 5 elements.

It runs ok the first time I try to run it (90%), but subsequent runs it crashes and I have to exit matlab to get it to work again?

Any input/help much appreciated.

Thanks

 

[VisiGoth]

return;


I also changed to

const char** fnames;

and also

fnames = mxCalloc(nfields, sizeof(*fnames));


but I think it was the return; as the inal insruction that did the trick.

 

[shetlandbob]

Try running it more than once, close matlab open again and run without recompiling a number of times, I'll be surprised if it works.

Having said that the problem is fixed by using

mexMakeMemoryPersistent(array)