From: "Iñaki Baz Castillo" <ibc@...>
Date: 2012-05-10T20:23:30+09:00
Subject: Re: How to use Data_Wrap_Struct to assign the DATA VALUE to an exsiting Ruby object?

2012/5/10 Iñaki Baz Castillo <ibc@aliax.net>:
> C land:
> ----------
>
> VALUE MyModule_init_udp_socket(VALUE self, VALUE rb_bind_ip, VALUE rb_bind_port)
> {
>  [...]
>  struct my_udp_cdata* cdata = ALLOC(struct my_udp_cdata);
>
>  cdata->xxxx = xxxx;
>  cdata->xxxx = xxxx;
>
>  DATA_PTR(self) = cdata;
>
>  [...]
>  return self;
> }
>
>
> This still does NOT crash, but if after the C function I call to any
> attribute reader of _sock_ or use sock.instance_variable_set(), then
> it crashes.


DATA_PTR is defined as follows:


#define DATA_PTR(dta) (RDATA(dta)->data)
#define RDATA(obj)   (R_CAST(RData)(obj))
#define R_CAST(st)   (struct st*)

struct RData {
    struct RBasic basic;
    void (*dmark)(void*);
    void (*dfree)(void*);
    void *data;
};

struct RBasic {
    VALUE flags;
    VALUE klass;
};


So I think that using DATA_PTR(self) is not what I expected. IMHO it
completely replaces the current C data of the Ruby object, while the
only I want is to "attach" a C structure to a given Ruby object. Am I
right?

-- 
Iñaki Baz Castillo
<ibc@aliax.net>