[Pyrex] NoneType object is not callable in dealloc

[Lenard Lindstrom]

On 29 Sep 2005 at 20:57, AKX wrote:

> Hiya,
> 
> I'm making a rather large wrapper for a rather large library, but now
> I've reached an impasse...
> 
> When a program exits with an AlFont instance in memory, it crashes
> (Win32), emitting "Exception exceptions.TypeError: "'NoneType' object
> is not callable" in <_pyalleg.AlFont object at 0x009EC060> ignored".
> Through print debugging (arcane art, I say), I've found out it crashes
> in the debug() line. Other classes built similarly do not crash in a
> similar situation.
> 
> The responsible code follows (and the generated C is a bit abridged
> and formatted).
> 
> Does anyone have any pointers on how to fix this, or is it a Pyrex
> bug? (Always blame the tool developers... just kidding, Pyrex rocks.)
> 
> Thanks in advance,
> 
> AKX
> 
> --------------------------------------------------------------------------------
> 
> == _pyalleg.pyx snippet ==
> 
> cdef class AlFont:
> 	cdef ALFONT_FONT *f
> 	# SNIP
> 	def __dealloc__(self):
> 		if self.f!=NULL: # <-- line 825
> 			debug("Deallocating AlFont "+str(self))
> 			alfont_destroy_font(self.f) # void ... (ALFONT_FONT *)
> 			self.f=NULL
> 	# SNIP

It is possible the debug function is garbage collected before the AlFont instance. Try 
this:

cdef class AlFont:
    <cdefs>
    cdef object debug

    def __new__(self, ...): # or __init__
         self.debug = debug
         <other stuff>

    def __dealloc__(self):
         if ...
            self.debug("Deallocating AlFont" + str(self))

Making debug an attribute keeps it alive until the AlFont instance deallocated.

Lenard Lindstrom
<len-l at telus.net>