[Octave-bug-tracker] [bug #48949] mexCallMATLABWithTrap not implemented and problem with mexCallMATLAB/mexSetTrapFlag

[Guillaume]

URL:
  <http://savannah.gnu.org/bugs/?48949>

                 Summary: mexCallMATLABWithTrap not implemented and problem
with mexCallMATLAB/mexSetTrapFlag
                 Project: GNU Octave
            Submitted by: gyom
            Submitted on: Tue 30 Aug 2016 10:42:32 AM GMT
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
             Assigned to: None
         Originator Name: Guillaume
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

It seems that mexCallMATLABWithTrap is not available from the Octave API:
  http://www.mathworks.com/help/matlab/apiref/mexcallmatlabwithtrap.html

I tried instead to use mexCallMATLAB with mexSetTrapFlag, even if its use is
deprecated in MATLAB, as it seems to be implemented in Octave:
  http://www.mathworks.com/help/matlab/apiref/mexsettrapflag.html

There seems to be an issue with the integer value returned by mexCallMATLAB
though:


#include "mex.h"

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    int sts;
    
    mexSetTrapFlag(1); /* or 0 */
    sts = mexCallMATLAB(0, NULL, 1, (mxArray **)prhs, "fileread");
    mexPrintf("status = %d.\n", sts);
}


With mexSetTrapFlag(0), Octave gives:


octave:1> test_mexCallMATLAB('e') 
error: fileread: cannot open file
error: called from
    fileread at line 37 column 5


With mexSetTrapFlag(0), MATLAB gives:


>> test_mexCallMATLAB('e') 
Error using fileread (line 49)
Could not open file e. No such file or directory.


With mexSetTrapFlag(1), Octave gives:


octave:1> test_mexCallMATLAB('e') 
error: fileread: cannot open file
status = 0.


With mexSetTrapFlag(1), MATLAB gives:


>> test_mexCallMATLAB('e')
Error using fileread (line 49)
Could not open file e. No such file or directory.

status = 1.


So it seems that when the Trap Flag is set to true, mexCallMATLAB is not set
to a non-zero value when an error is caught.

>From what I see, it seems that having an implementation of
mexCallMATLABWithTrap might not be too difficult - the main issue being that
MException is not implemented: what are the plans regarding this and should it
be implemented in M-code or C++?




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