Why when I add mxDestroyArray(myArray) to my code MATLAB crashes?

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Dear All,
I have a problem with using mxDestroyArray. When I add it to my code, MATLAB crashes. Shouldn't I destroy any mxArray that I declared in my code just to avoid memory leak? Shouldn't each mxArray *myArr correspond to a mxDestroyArray(myArr) when the array is no longer needed?
Thanks,
Ahmd
  1 Comment
James Tursa
James Tursa on 24 Oct 2012
Please post the offending code (or a small subset of it that reproduces the problem) so we can comment on it.

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Answers (2)

Kaustubha Govind
Kaustubha Govind on 24 Oct 2012
You should only call mxDestroyArray on locally created mxArrays that are not being returned in plhs. Are you deleting mxArrays that are present in either prhs or plhs?
  2 Comments
Kaustubha Govind
Kaustubha Govind on 25 Oct 2012
Okay. In that case, I would second James Tursa's suggestion to post the offending code.

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Andrew Stamps
Andrew Stamps on 15 Feb 2013
Does your mxArray happen to contain a Java object? I recently discovered the hard way that calling mxDestroyArray() on an mxArray that contains a Java object will cause a crash, even if you otherwise should call mxDestroyArray().
If you clear the pointer to the Java object before calling mxDestroyArray(), then it doesn't seem to crash, although I don't know if there are other ramifications.
e.g.:
mxSetData(myArr, NULL);
mxDestroyArray(myArr);
  2 Comments
Andrew Stamps
Andrew Stamps on 16 Feb 2013
I encountered this when calling a C shared library generated by the MATLAB Compiler, so maybe this doesn't apply to mex functions as well, but here's a sample function where the error occurs:
static long getNumberOfStreams(const INTEGER instanceHandle)
{
long iLength;
mxArray *numStreams = NULL;
mxArray *streamArray = NULL;
if (!mlfGetStreams(2, &streamArray,
&numStreams, domArray[instanceHandle])) {
return 0;
}
iLength = (long) *(mxGetPr(numStreams));
mxDestroyArray(streamArray); // Why does this cause a crash?
mxDestroyArray(numStreams);
return (iLength > 0) ? iLength : 0L;
}
In its intended use, the input array domArray[instanceHandle] is of class org.apache.xerces.dom.DeferredDocumentImpl and is held in global memory. I am not using the first output argument from the function, streamArray, but it should hold an object of class org.apache.xerces.dom.DeepNodeListImpl. The second output argument is a standard scalar double. If I call mxDestroyArray on streamArray without mxSetData(streamArray, NULL) first, then I get a segmentation fault.
Thanks.

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