Re: [Boost-users] [smart_ptr] Conflict with Maya?

From: Paul Giaccone (paulg_at_[hidden])
Date: 2007-04-19 05:19:17

Peter Dimov wrote:

>Paul Giaccone wrote:
>
>  
>
>>1. The creator function, required by Maya. Note the absence of a smart
>>pointer. I tried wrapping this in a shared_ptr and returning .get()
>>but this caused a crash, if I remember rightly.
>>
>>void* MyNode::creator(void)
>>{
>>   return new MyNode();
>>}
>>    
>>
>
>This is, I think, exactly as it should be. Maya expects to take ownership of 
>the returned pointer and will delete it when it decides that it's no longer 
>needed. But I'm not an expert on that; you probably need to ask in a Maya 
>SDK forum to be sure. 
>  
>

A bit of research and feedback from HighEnd 3D's Maya API forum suggests 
that this is the case - you create the node and Maya takes 
responsibility deleting it when necessary. Apparently, Maya owns the 
node and deletes it itself when it feels like it, not when the 
programmer says so.

If I've understood correctly, this means that any memory allocated on 
the heap in MyNode must be done using bare pointers rather than smart 
pointers, so that Maya can delete it when it wants, not when the smart 
pointers say the memory can be released. MyNode and any objects that it 
allocates on the heap still need to have destructors to deallocate their 
contents, but it is up to Maya when the destructor for MyNode is called.

Not an ideal state of affairs (once you've experienced smart pointers, 
you never want to go back to the inconvenience of having to work out 
where the all the deletes need to go), but then I've found that Maya is 
hardly the most programmer-friendly system, IMO.