Re: Illegal instruction on layers of callback wrappers

On Thu, 12 May 2011 18:01:09 -0500, Thomas Stover
<[email protected]> wrote:

For the searchers and list miners, I figured it out.

> 
> 	def __init__(self, callback_variable):
...
> 		callback = CALLBACK_TYPE(self.CallbackWrapper)
>		self.use_callback(self.callback)


It's hard to mix C and Python and not think like C. Anyway, here the
variable "callback" is not like a C pointer, it is an object that provides
the shim, context, etc. Sense the variable is local to the __init__()
function, it is dereferenced and freed. Changing that to self.callback
will
hold the reference and everything works fine. It makes sense that there
would be no way ctypes would know to increase that reference count just by
handing C a callback, because that would leak in most cases without an
explicit "not needed anymore" notation.

Darn high-level language interpretation! I like it too, but sometimes on
stuff like this, the lines saved from C's verbosity, are just moved onto
all the things you have to keep track of in your mind. :) 

-- 
www.thomasstover.com
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