[Python-Dev] Functions that steal references (Re: [pygame] [patch] minor memory leaks...)

[Hrvoje Niksic]

Christian Heimes wrote:
>>>> I assumed that since PyModule_AddObject is documented as stealing a
>>>> reference, it always stole a reference. But in reality it only does so
>>>> conditionally, when it succeeds.
>>> As an aside, is this a general feature of functions
>>> that steal references, or is PyModule_AddObject an
>>> oddity?
>> 
>> IIRC, It's an oddity.
> 
> But it is a convenient oddity nonetheless.

Stealing references is sometimes convenient, but Greg was referring to 
functions that steal references *conditionally*, which is indeed an 
oddity.  Most functions and macros that steal references do so 
unconditionally, typically because they can't fail anyway.  Conditional 
stealing of references requires very careful thinking on the side of 
callers that care about not leaking references in the face of 
exceptions.  See http://bugs.python.org/issue1782 for an example.