Re: [Swig-user] Serious bug with Lua and C++ typename check ??

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

Sebastian Wolff wrote:
> Hello everybody,
> 
> I think I have found a serious bug in the Lua bindings of SWIG and hope 
> you someone else also encountered this problems and found a solution 
> for this.
> 
> Suggest you have two SWIG modules, "A" and "B". Also suggest you use 
> different namespaces in both modules with equally named classes, say:
> 
> library A:
> 
> namespace A
> {
>   class classname
>   {
>     //! constructor
>     classname(const std::string & ident);
>     ...
>   };
> }
> 
> and library B:
> 
> namespace B
> {
>   class classname
>   {
>     //! constructor
>     classname(const int & id);
>     ...
>   };
> }
> 
> Then both libraries will be wrapped by SWIG into 2 different modules 
> and linked together. In Lua, you expect to be able to call:
> 
> a = A.classname("hello") -- call constructor of A::classname
> b = B.classname( 3 ) -- call constructor of B::classname
> 
> SWIG actually merges equally class names from different namespaces into 
> one. That is, if the load_module routine of module A was called before 
> B, then it expects the syntax of A::classname, if B.classname( ... ) is 
> called.
> 
> I am using latest SWIG 1.3.40
> 
> Any help or suggestions?
> 
> I asked here, because the bug tracker on sourceforge is quite inactive 
> regarding Lua...
There isn't anyone around at the moment who is working on Lua, so until 
someone volunteers not much is likely to happen for Lua.

However, I took a look at this and this is a general problem that is not 
Lua specific. I'm assuming your 2nd module will %import a file 
containing A::classname, and %include a file containing B::classname. 
The problem is SWIG flattens the namespaces and so it is not possible to 
wrap classes of the same name unless you rename one of them. If you 
%include both of these class definitions you will get a warning telling 
you that one has been ignored. However, there is no warning generated 
with a %import and a %include when the symbol names would clash in the 
target language. That is arguably a bug. Also there are some strange 
side effects when using %include and %import of an identical type, which 
should give an error or warning. Something else to do.

William