Solved GetCache() bug

merkvilson

Hello PluginCafe

I tried to insert a cache of selected object into the doc via Console but I got this error/crash.

alt text

doc.InsertObject(op.GetCache())

is it possible to bypass this behavior?

s_bach

Hello,

this is no bug of the Python API. The code is just unsafe.

A given BaseObject (generator) owns the content of its cache. This cache may be a BaseObject (and subsequent child objects) or nothing - None.

So if you operate with a cache you should always check if that cache is actually set. GetCache() can always return None.

cache = op.GetCache()
if cache is None:
    return

But the real problem is that the given BaseObject owns the content of the cache. In your code, you take the cache and inset it into the BaseDocument. Both the generator and theBaseObject now think they do have sole ownership of the cache content. This can't work and is a perfect recipe for any kind of undefined behaviour - including a crash.

So you cannot insert the cache into the BaseDocument. You must create a copy of the cache (GetClone()) and insert that copy into the BaseDocument.

best wishes,
Sebastian

merkvilson

Thanks, Sebastian for detailed explanation
But this still can be considered as a bug since it CRASHES c4d instead of raising an error message.

m_adam

Hi @merkvilson, this feedback has been communicated to our development team.

Cheers,
Maxime.