[ruby-talk:5448] Re: rb_gc_mark error message

Hi,

At Wed, 11 Oct 2000 14:37:06 +0200 (MET DST),
Robert Feldt <[e-mail]> wrote:
> > Can you see me the whole code which cause this error?
> > 
> Sorry but thiss will be very difficult; it's part of a rather large system
> and parts of it are proprietary so I'm not allowed to pass them on.
> 
> If I'm able to isolate the bug I'll send it to you. In the mean time:

OK.

> * Is there any way I can make this happen by not handling Data_Wrap_Struct
> in the right way? I have a number of extension libraries and I'm not sure
> I setup the mark functions in the right way.

If your struct has VALUE members, you have to mark the members by
rb_gc_mark() in the mark functions. Otherwise such members will
be collected as garbage.

ex).

struct foo {
    int count;
    VALUE obj;
};

static void mark_foo(struct foo *f)
{
    rb_gc_mark(f->obj);
}

static VALUE foo_s_new(VALUE self)
{
    ...
    Data_Wrap_Struct(cFoo, mark_foo, free_foo, f);
    ...
}

You must not mark non-VALUE members.
If the struct has no VALUE members, you don't have to set the
mark function. Just specify NULL (or 0 --- matz style).

Shugo