Re: [Swig-user] bug wrapping template

[Stefan Z. <sz...@gm...>]

On Mon, Oct 31, 2011 at 1:51 PM, Marco Correia
<mar...@gm...> wrote:
> Hi Stefan,
>
> Thank you for your reply.
>
> I'm afraid I don't agree with you. There are two separate classes with
> different methods which I want to wrap. One is Expr<int>, which I want to wrap
> as IntExpr, and another is Expr<Seq<int>> which I want to wrap as IntSeqExpr.

Sorry, my mistake -- I didn't look closely enough at the error output.
 I agree that this is incorrect behavior, and I suggest you file a
bug.

Having said that, keep in mind that SWIG doesn't claim to do 100%
faithful processing of templates.  The usage in your example is a bit
esoteric, so I can't say for certain that anyone will volunteer to fix
it.

You may be able to work around it by putting something like this in
your interface, before the class declarations:

%ignore Expr<Seq<int> >::method1;

Stefan


>
> It happens in this example that IntExpr and IntSeqExpr have a different set of
> methods, which is no problem to SWIG if they were coming from unrelated
> classes. In this case they correspond to two specializations of a single
> template, and, in my opinion, they should be treated as different classes also.
> Templates are used to expand source code, there is nothing related to
> inheritance here.
>
> Thanks again
> Marco
>
> On Monday 31 October 2011 20:42:59 you wrote:
>> I think the error is in your code, not in swig.  The rules of template
>> specialization dictate that method1 is *not* defined for Expr<Seq<int>
>>
>> > as you have written it.  I think you may be confusing inheritance
>>
>> with template specialization.
>>
>> Hope that helps.
>>
>> Stefan
>>
>> On Mon, Oct 31, 2011 at 8:12 AM, Marco Correia
>>
>> <mar...@gm...> wrote:
>> > I think I found a bug. Consider the following example module called
>> > mytest:
>> >
>> > %module mytest
>> > %inline %{
>> >
>> > template<class T> struct Seq;
>> >
>> > template<class E>
>> > struct Expr
>> > {
>> >  Expr() {}
>> >  void method1() { }
>> > };
>> >
>> > template<class E>
>> > struct Expr<Seq<E> >
>> > {
>> >  Expr() {}
>> >  void method2() { }
>> > };
>> >
>> > %}
>> >
>> > %template(IntExpr) Expr<int>;
>> > %template(IntSeqExpr) Expr<Seq<int> >;
>> >
>> > Compiling gives:
>> >
>> > swig -o mytest_wrap.cpp -c++ -python mytest.i
>> > ok.
>> >
>> > g++ -o mytest_wrap.os -c -g3 -O0 -Wall -fPIC -I/usr/include/python2.7
>> > mytest_wrap.cpp
>> >
>> > errors:
>> > mytest_wrap.cpp: In function ‘PyObject*
>> > _wrap_IntSeqExpr_method1(PyObject*, PyObject*)’:
>> > mytest_wrap.cpp:2896:11: error: ‘struct Expr<Seq<int> >’ has no member
>> > named ‘method1’
>> >
>> > It seems that SWIG is not finding the proper template specialization. I'm
>> > attaching the source mytest.i.
>> >
>> > Thanks!
>> > Marco
>> >
>> > --
>> > Marco Correia <mv...@ne...>
>> >
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>
> --
> Marco Correia <mv...@ne...>
>