From: ptkwt@... (Phil Tomson)
Date: 2004-08-19T08:35:54+09:00
Subject: Re: swig problem with init

In article <20040818221509.GA70952@freeze.org>,  <jim@freeze.org> wrote:
>I have an innocuous swig/ruby case that is causing me some grief.
>The problem is probably obvious, but I'm not seeing the solution
>right now.
>
>I have a .i file that defines a module 
>
>     cat itkdb.i
>    /* itkdb.i */
>    %module ITKDb
>
>    %{
>    %}
>
>This generates a wrapper with the following lines of interest:
>
>    #define SWIG_init    Init_ITKDb
>    #define SWIG_name    "ITKDb"
>
>    #ifdef __cplusplus
>    extern "C"
>    #endif
>    SWIGEXPORT(void) Init_ITKDb(void) {
>        int i;
>
>        SWIG_InitRuntime();
>        mITKDb = rb_define_module("ITKDb");
>
>        for (i = 0; swig_types_initial[i]; i++) {
>            swig_types[i] = SWIG_TypeRegister(swig_types_initial[i]);
>            SWIG_define_class(swig_types[i]);
>        }
>
>    }
>
>I compile this against a vendor supplied library and try to load the .so
>file and get:
>
>    ruby -r itkdb -e {}
>    ./itkdb.so: /usr/lib/libruby.so.1.8: undefined symbol: Init_itkdb -
>    ./itkdb.so (LoadError)
>
>Can someone tell me what I'm doing wrong here?
>

Hmmmmm...
Some quick guesses:

In your wrapper file you've got this declaration:

>    SWIGEXPORT(void) Init_ITKDb(void) {

While the error says it's looking for the symbol:
  Init_itkdb
-------^^^^

So there seems to be a mismatch between ITKDb and itkdb...

I would try changing the .i file to:

 %module itkdb
    
    %{
    %}
      

Although it does seem a bit backward... If I recall correctly, what 
happens is that when you define '%module itkdb' you'll get a Ruby module 
called Itkdb (uppercased).  In your case you called it ITKDb and it seems 
to have lowercased it.


What happens when you do:
  nm itkdb.so | grep Init

?  Does it have entries for both Init_ITKDb (defined) and 
Init_itkdb (undefined)?

Also, what version of swig are you running?

Phil