From: Paul Brannan <pbrannan@...>
Date: 2002-04-19T08:00:56+09:00
Subject: GC problem in C++ extension

I have a test program that looks like this:
  #include <string>
  #include <iostream>
  #include <ruby.h>
  #include <intern.h>
  
  #if defined(RUBY_METHOD_FUNC)
  #undef RUBY_METHOD_FUNC
  #endif
  typedef VALUE (*RUBY_METHOD_FUNC)();
  
  class Foo
  {
  public:
    Foo(char const * s) : s_(s) { }
    ~Foo() { std::cout << s_ << std::endl; }
    static void free(Foo * f) { delete f; }
  private:
    std::string s_;
  };
  
  VALUE test_foo(VALUE)
  {
    Foo * f = new Foo("testing...");
    VALUE v = Data_Wrap_Struct(rb_cObject, 0, (RUBY_DATA_FUNC)Foo::free, f);
    return Qnil; // line 25
  }
  
  int main(int argc, char * argv[])
  {
    ruby_init();
    ruby_init_loadpath();
    ruby_options(argc, argv);
    rb_define_global_function("foo", RUBY_METHOD_FUNC(test_foo), 0);
    ruby_run();
  }

I run it like this:
  ./test5 -e 'foo; GC.start; puts "exiting..."'

I see output like this:
  exiting...
  testing...

I would rather see output like this:
  testing...
  exiting...

and, in fact, I do see that if I delete line 25.  How can I make sure
that the allocated Foo object gets properly destructed?

Paul