Re: memory leak

[Muthiah Annamalai]

On 5/23/07, Michael Prinzinger <address@hidden> wrote:
> Good Day!
>
> I have a problem with Octave potentially causing memory leaks.
> I use liboctave in a C++ project with matrices.
> The problem occurs, when I try to read a matrix, which I have saved previously.
>
> Please have a look on the following code:
>
> FILE* eigenmatrix_file = fopen(filename, "w");
> if(eigenmatrix_file == NULL)
> {
>      throw fileException("Error! in EigenMatrix::save(): can't open file!");
> }
>
> MArray2<Complex>* m_array = new MArray2<Complex>(this->row, this->column, *(new 
> Complex(0.0, 0.0)));
> fread(m_array, sizeof((*m_array)(0)), sizeof(m_array), eigenmatrix_file);
>
>
> This code runs fine with small matrices, and I have no problems whatsoever.
> However after I try it with "real" matrices coming from 80x80 images I want to 
> work with (80x80 = 6400 values per image, that means 6400 x 6400=40960000 values or the 
> matrix),
> I get a segmentation fault accessing "eigenmatrix_file" after I created m_array.
> Fidling with the above code, I noticed that even a simple call like
>
> eigenmatrix_file;
> or
> (eigenmatrix_file == NULL);
>
> causes a seg fault after the creation of m_array.
>
> I tried decalring m_array at the very beginning, before I declare and 
> initialize File* eigenmatrix_file, but even in this case, calling the resulting 
> pointer with the statements above (so no dereferencing, just calling the 
> pointer!) causes again a seg fault.
>
> If I outcomment
> // MArray2<Complex>* m_array = new MArray2<Complex>(this->row, this->column, 
> *(new Complex(0.0, 0.0)));
> I don't get this seg fault.
>
> So I have come to the conclusion, that creating
> a new MArray2<Complex>(this->row, this->column, *(new Complex(0.0, 0.0)));
> where row and column are pretty large,
> causes Octave to somehow destroy my C++ stack, at least my previously defined 
> variables get lost.
>
> Note that in general Octave has no problem with large matrices in my programm.
> If the file "filename" does not exist the corresponding matrix is computed and 
> saved without error, only after trying to load a matrix this large, this error occurs.
>
> I hope you can help, I really need to solve this one, to be able to hand in my 
> university project ;)
> Thank You
>
> Michael Prinzinger
> _______________________________________________________________
> SMS schreiben mit WEB.DE FreeMail - einfach, schnell und
> kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192
>
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://www.cae.wisc.edu/mailman/listinfo/help-octave
AFAIK you cannot use exception handling in Octave. If you searched
the mailing lists, JWE has explained many times that Octave was written
at a time C++ didnot support exceptions!

So the code in your file handler must be written to set error_state if required,
and should exit by a statement like:

return octave_value("cannot open file ");

instead of the throw.

I think this could fix the problem. Atleast prevent the segfaults.
-Muthu