Re: [Swig-user] Vector of const pointers

[William S F. <ws...@fu...>]

Nitro wrote:
> I did some experimentation on this, below is my interface file I used
> for testing (1.3.31, hope that doesn't make a difference).
>
> The problem appears because the const and non-const versions trigger
> different templates in std/std_vector.i. The const version uses the
> first template defined in this file, the non-const version uses the
> lower one which is tagged with this note:
>
>   // ***
>   // This specialization should dissapear or get simplified when
>   // a 'const SWIGTYPE*&' can be defined
>   // ***
>
> The difference between those templates is that they generate different
> traits each. The trait that needs to be presented in the final file is
>
>   namespace swig {
>     template <>  struct traits<Calendar > {
>       typedef pointer_category category;
>       static const char* type_name() { return"Calendar"; }
>     };
>   }
>
> The fix marcelo checked in makes sure that "const* type" resolve to the
> "type" trait. Now the const version generates an improper trait for
> "const* type". That's why the compiler will later complain that it can't
> find the type_name() for Calendar as there is only a trait for const
> Calendar*.
> The two lines in the code below fix the problem apparently. The
> generated code compiles fine and I can load the wrapper. I can do this:
>
> import problem
> v = problem.VectCalendar()
> problem.foo(v)
>
> and it will print "foo called".
> Doing
>
> c = problem.Calendar()
> problem.append(c)
>
shouldn't this read
  v.append(c)
?
I think that the const Calendar * container should be different to the 
non-const one. They are separate beasts in the Java/C# modules, so we 
may as well keep that consistent. However, adding to the container 
should be possible.

> does not work, because Calendar is not a const Calendar (I guess). I am
> not sure if this is supposed to work at all. Maybe you can comment on 
> this.
>
> Finally, I am not sure whether this "fix" only fixes the apparent
> problem or if there's a much deeper problem with const vectors somewhere
> under the covers.
>
Matthias, this is great. I'll try this out tomorrow, but meanwhile is 
there any chance of making a patch to pycontainers.swg so that it is 
fixed for everyone and then I can test it on the entire test-suite?


William