Re: cdata finalizer called twice
- From: Peter Colberg <peter@xxxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 14 Nov 2014 17:28:21 -0500
On Thu, Nov 13, 2014 at 10:58:49PM -0500, Peter Colberg wrote:
> After some experimentation I found that duplicate finalization occurs
> only when ffi.gc() is both compiled and invoked in a tail call.
>
> This method of constructing objects works fine:
>
> ffi.cdef[[typedef struct _cl_event *cl_event;]]
>
> local event_ptr = ffi.new("cl_event[1]")
>
> local function enqueue_marker(queue)
> assert(C.CL_SUCCESS == C.clEnqueueMarker(queue, event_ptr))
> local event = ffi.gc(event_ptr[0], release_event) -- no tail call
> return event
> end
>
> This method of constructing objects causes duplicate finalization:
>
> local function enqueue_marker(queue)
> assert(C.CL_SUCCESS == C.clEnqueueMarker(queue, event_ptr))
> return ffi.gc(event_ptr[0], release_event) -- tail call
> end
To confirm that the tail call is exposing this behaviour:
Finalization works fine if the tail call is avoided using ()
local function enqueue_marker(queue)
assert(C.CL_SUCCESS == C.clEnqueueMarker(queue, event_ptr))
return (ffi.gc(event_ptr[0], release_event))
end
or if the finalizer is set outside of the function
local function enqueue_marker(queue)
assert(C.CL_SUCCESS == C.clEnqueueMarker(queue, event_ptr))
return event_ptr
end
-- repeated calls in program loop
ffi.gc(enqueue_marker(queue)[0], release_event)
Peter
Other related posts:
