[Octave-bug-tracker] [bug #51725] Adding mxGetProperty to Matlab API

[Rik]

Follow-up Comment #12, bug #51725 (project octave):

I also did some tests with NULL pointers to mxArray to see how they should
behave.  It would be *very* good if someone could test in Matlab to see if
Octave is compatible.  The summary is that a NULL pointer seems to yield an
empty 0x0 matrix.

nulltst.c:


#include "mex.h"

void mexFunction (int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
  if (nlhs < 1)
    mexErrMsgTxt ("Must have at least one output");

  mexPrintf ("plhs[0] initialized to %ld\n", plhs[0]);

  plhs[0] = NULL;
}


And when executed


octave:1> mex nulltst.c
octave:2> x = nulltst
plhs[0] initialized to 0
x = [](0x0)
octave:3> [x,y,z] = nulltst
plhs[0] initialized to 0
x = [](0x0)
y = [](0x0)
z = [](0x0)


So it seems that the plhs array of pointers is always initialized to 0 (NULL).
 And that the interpretation of a NULL pointer to an mxArray is always an
empty double matrix in Octave.  



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