Re: FFI - coroutine.yield/resume inside callback
- From: demetri <demetri.spanos@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 25 May 2012 11:02:45 -0700
Thanks Michael, after you pointed it out it was embarrassingly obvious. The
GC follows *table* references; references from another ffi object do not
prevent GC.
On Fri, May 25, 2012 at 12:59 AM, Michal Kottman <k0mpjut0r@xxxxxxxxx>wrote:
> On 24 May 2012 10:01, Richard Hundt <richardhundt@xxxxxxxxx> wrote:
> > Just a heads up, it works beautifully :)
> >
> > However, this is what bit me: you can't keep a reference to a member of
> the object returned via ffi.load after the object itself has been garbage
> collected.
> >
> > function loadlib()
> > local mylib = assert(ffi.load('mylib')) -- mylib gets GC'ed eventually
> > return { some_function = mylib.mylib_some_function }
> > end
> >
> > local l = loadlib()
> > l.some_function() -- sooner or later doing this is going to blow up when
> mylib above gets collected
>
> I've been hit by this more than once (forgetting to save a reference).
> Basically I have a Lua C function which returns a userdata filled by
> some data, which I later ffi.cast() to a more appropriate type in Lua.
> The problem was that I never saved the reference to the userdata,
> which was then garbage collected.
>
> The main point to remember: save a reference along with the casted data.
>
> local points = mylib.calculatePoints()
> return {
> points_ptr = points, -- keep a reference so it is not garbage collected
> points = ffi.cast('Point*', points)
> }
>
> Your case is a similar issue to this one.
>
>
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