160567 - Documentation: add comments explaining possible crash in scriptable object code

Status: RESOLVED INCOMPLETE

(Core Graveyard :: Plug-ins, defect)

Description

[av (gone)]

A comment should be added to the paragraph Making Plug-ins Scriptable in
implementation example of NPP_Destroy function. Here is what I just added to the
article http://mozilla.org/projects/plugins/scripting-plugins.html from where
the code was actually taken:

NPError NPP_Destroy (NPP instance, NPSavedData** save)
{
  if(instance == NULL)
    return NPERR_INVALID_INSTANCE_ERROR;

  // release the scriptable object 
+ // Note that even though we release it here it does not necesserely
+ // mean that its refcount will go to zero and it will be deleted.
+ // XPCOM code in the browser may still hold more outstanding 
+ // references to this object and even execute calls to it at some
+ // later time, when other plugin objects no longer exist. So in real 
+ // implementations some measures of precaution must be taken here to 
+ // prevent crash such as notifying the scriptable object that there
+ // may be some dangling pointers and it is not safe to use them any more
  NS_IF_RELEASE(instance->pdata);
}

Comment 1

[Ian Oeschger (gone)]

moving stuff over to an outside-the-firewall email for the time being, looking
for people to pick these Help and doc bugs up for me.

Comment 2

[Daniel Wang]

taking over some of Ian's bugs

Comment 3

[Benjamin Smedberg]

XPCOM plugins are gone.