Re: basic DLD help?

[Paul Kienzle]

You have to be careful with this.  You may accidentally free the data
behind the pointer before it is used.  fortran_vec() calls 
make_unique(),
so it may not return the same pointer as referred to in args(0), but
instead return a pointer which is cleaned up when the temporary
args(0).vector_value() destructor is called.

Better would be to use:

        RowVector y(args(0).vector_value());
        double *py = y.fortran_vec();

- Paul

On Jul 12, 2005, at 8:44 AM, Shai Ayal wrote:

> Hi all,
>
> I am probably missing something basic here, but why does this not work?
>
> [bash] > cat > test.cc
> #include "oct.h"
>
> DEFUN_DLD (test, args, ,"")
> {
>
>   double* y = args(0).vector_value().fortran_vec();
>
>   octave_stdout << ">> " << y[0] << "," << y[1] << "\n";
>
>
> }
> EOF
>
> [bash] > mkoctfile -v test.cc
> g++ -c -fPIC -I/usr/local/include/octave-2.1.71 
> -I/usr/local/include/octave-2.1.71/octave -I/usr/local/include 
> -mieee-fp -g -O2 test.cc -o test.o
> g++ -shared -Wl,-Bsymbolic -o test.oct test.o 
> -L/usr/local/lib/octave-2.1.71 -loctinterp -loctave -lcruft -lcblas 
> -lf77blas -latlas -lfftw3 -lreadline -lncurses -ldl -lm 
> -L/usr/lib/gcc-lib/i386-redhat-linux/3.3.2 
> -L/usr/lib/gcc-lib/i386-redhat-linux/3.3.2/../../.. -lfrtbegin -lg2c 
> -lm -lgcc_s
>
>
> [bash] > octave
> GNU Octave, version 2.1.71 (i686-pc-linux-gnu).
> Copyright (C) 2005 John W. Eaton.
> This is free software; see the source code for copying conditions.
> There is ABSOLUTELY NO WARRANTY; not even for MERCHANTIBILITY or
> FITNESS FOR A PARTICULAR PURPOSE.  For details, type `warranty'.
>
> Additional information about Octave is available at 
> http://www.octave.org.
>
> Please contribute if you find this software useful.
> For more information, visit http://www.octave.org/help-wanted.html
>
> Report bugs to <address@hidden> (but first, please read
> http://www.octave.org/bugs.html to learn how to write a helpful 
> report).
>
> octave:1> a=[1,2,3];
> octave:2> test(a)
> panic: Segmentation fault -- stopping myself...
> >> 1,2
> attempting to save variables to `octave-core'...
> save to `octave-core' complete
> Segmentation fault
>
>
>
>
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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
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