Re: basic DLD help?

[David Bateman]

Paul Kienzle a écrit :

> 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();

Even better would be

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

since as you say fortran_vec calls make_unique except when "const", and 
since you aren't altering the data past to the function, in this manner 
you avoid a copy.

D.



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