[PyQt] Guaranteed avoidance of C++ destructor call

[John Lee]

On Thu, 30 May 2013, Phil Thompson wrote:

> On Thu, 30 May 2013 22:49:24 +0100 (BST), John Lee <jjl at pobox.com> wrote:
>> Hi
>>
>> Is it possible to guarantee that a C++ destructor of a QObject wrapped by
>> PyQt is never called?
[...]
>> If I can't guarantee that from PyQt, can I write a simple sip wrapper that
>> will achieve the same end, without copying and pasting the Qt code?
>
> sip.setdestroyonexit() might do what you want.

Thanks, that sounds promising.  It does trigger some followup questions:


If I call sip.setdestroyonexit(False) before I construct any QProcess 
Python instances, can ~QProcess still be called for any reason, even if I 
ensure that:

1. no Qt code deletes the C++ object, and

2. my code does not call sip.delete(), and

3. I create a module-global reference (my module) to the wrapping 
QtCore.QProcess Python instance which I never explicitly unbind (but for 
all I know might get unbound by some part of the PyQt/sip/Python shutdown 
process)?


Other than the usual QObject parent/child hierarchy, are there any cases 
where Qt deletes things, that might surprise me?


Since setdestroyonexit affects all cleanup and not only that of QProcess: 
Are there other notable side effects that you or others know of that I 
might notice / be surprised by from calling sip.setdestroyonexit(False), 
as a result of the lack of the usual cleanup associated with particular Qt 
classses?  In other words, what cases are known / can be guessed at where 
my program might start causing a leak of OS resources like temporary 
files, or badly terminated network connections, etc?


John