From: Colin Steele <colin@...2.com>
Date: 2001-04-12T05:47:59+09:00
Subject: [ruby-talk:13610] Data_Get_Struct wants a DATA... but I don't have one?


I've got a headscratcher for y'all.  I have a C extension which uses
Data_Make_Struct, and then calls rb_obj_call_init.  In my init
function, I try to pull out my data pointer using Data_Get_Struct, but
it pukes in rb_check_type, claiming I'm passing it the wrong type of
data.

This is almost identical to the example in the pickaxe book... what am
I missing?

Any help is greatly appreciated.



Here's the output (the problem):

colin@ska$ ruby extconf.rb
creating Makefile
colin@ska$ make
gcc -fPIC -g -O2 -fPIC  -I/usr/local/lib/ruby/1.6/i686-linux -I/usr/local/include    -c -o foo.o foo.c
gcc -shared  -L/usr/local/lib/ruby/1.6/i686-linux -L/usr/local/lib  -o foo.so foo.o -L. -lruby -lc 
colin@ska$ ruby ./test.rb 
./test.rb:3:in `initialize': wrong argument type XXX::Process (expected Data) (TypeError)
	from ./test.rb:3:in `new'
	from ./test.rb:3
colin@ska$ 
----------------------------------------------------------------------
Here's the ruby test:

require "foo"

foo = XXX::Process.new(42)

----------------------------------------------------------------------

Here's the C code:

#include "ruby.h"

VALUE mXXX;
VALUE cProcess;

struct _foo {
    int something;
};

typedef struct _foo foo;

VALUE
process_init(VALUE self, VALUE pid)
{
    foo *ptr;

    Data_Get_Struct(self, foo, ptr);

    return self;
}

VALUE
process_new(VALUE class, VALUE thePID)
{
    foo                        *ptr;
    VALUE                       tdata;

    tdata                       = Data_Make_Struct(class,
                                                   foo,
                                                   0,
                                                   0,
                                                   ptr);
    Data_Get_Struct(tdata, foo, ptr);
    
    return tdata;
}

void Init_foo() {
    mXXX = rb_define_module("XXX");
    cProcess = rb_define_class_under(mXXX, "Process", rb_cObject);
    rb_define_method(cProcess, "initialize", process_init, 1);
    rb_define_method(cProcess, "new", process_new, 1);

}


-- 
Colin Steele
colin@webg2.com / www.colinsteele.org / www.rubycookbook.org


		   From "The Hacker's Dictionary":
   softy: [IBM] n. Hardware hackers' term for a software expert who
	  is largely ignorant of the mysteries of hardware.