From: google@... (Bheeshmar Redheendran)
Date: 2004-03-26T12:04:28+09:00
Subject: Ruby/DL and C++ libraries

I'm trying to use a C++ shared library from Ruby and wanted to use
Ruby/DL to do it.  It seemed straightforward enough, but I can't seem
to match the signature on the function I want to import.

Here's a simplified example:
-------------------------------------------------------------------
bash $ cat dlexample.cpp
#include <iostream>
#include <string>

extern "C" void place( const std::string &text)
{
        std::cout << text << std::endl ;
}
bash $ cat dlexample.rb
require 'dl/import'
module Test
        extend DL::Importable
        dlload 'dlexample.so'

        typealias 'string', 'p'
        extern "void place(string)"
end

Test.place("text")

bash $ g++ -shared -fPIC -o dlexample.so dlexample.cpp
bash $ LD_LIBRARY_PATH="." ruby dlexample.rb
(eval):5: [BUG] Segmentation fault
ruby 1.8.1 (2004-02-06) [x86_64-linux-gnu]

Aborted
-------------------------------------------------------------------

It works with C functions (change the "const std::string &" to a
"const char *" and it's all good).

I have a feeling this can work with the write typealias and encoding
functions, but I'm fairly new to Ruby and would appreciate any
pointers.

I have a workaround in place using Swig, but if I go that route, I may
as well just code up the utility in C++.

Thanks in advance,
Bheeshmar Redheendran