Re: cdata finalizer called twice
- From: Peter Colberg <peter@xxxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Sun, 16 Nov 2014 02:03:05 -0500
Hi,
Finally I discovered why some cdata objects were finalized twice.
To query information about OpenCL objects, I use a common function
local function get_info(obj_info)
return function(obj, name)
return obj_info[name](obj)
end
end
to generate dispatch closures for different sub-method tables, e.g.
ffi.metatype("struct _cl_mem", __index = {
get_info = get_info({
type = get_mem_object_info_type,
flags = get_mem_object_info_flags,
size = get_mem_object_info_size,
}),
})
ffi.metatype("struct _cl_event", __index = {
get_profiling_info = get_info({
queued = get_event_profiling_info_queued,
submit = get_event_profiling_info_submit,
start = get_event_profiling_info_start,
["end"] = get_event_profiling_info_end,
})
})
Invoking both _cl_mem.get_info() and _cl_event.get_profiling_info()
within a loop results in undefined behaviour; in this case it may
cause duplicate finalization of '_cl_event *' objects.
Rewriting the object methods as follows resolves the issue:
local mem_info = {
type = get_mem_object_info_type,
flags = get_mem_object_info_flags,
size = get_mem_object_info_size,
}
ffi.metatype("struct _cl_mem", __index = {
get_info = function(mem, name)
return mem_info[name](mem)
end,
})
local event_profiling_info = {
queued = get_event_profiling_info_queued,
submit = get_event_profiling_info_submit,
start = get_event_profiling_info_start,
["end"] = get_event_profiling_info_end,
}
ffi.metatype("struct _cl_event", __index = {
get_profiling_info = function(event, name)
return event_profiling_info[name](event)
end,
})
Is the undefined behaviour in the first case expected?
The documentation of ffi.metatype() states that the contents of the
metatable and the contents of the __index table may not be modified
afterwards. Does this include that methods in the __index tables of
different ctypes may not be closures created from the same function?
Peter
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