Do Not Allow Static Objects to be Deallocated

The runtime currently has many objects that are statically defined. See Include/internal/pycore_global_objects.h. For the singletons, all instances of the type are statically defined. Otherwise only some instances are.

The problem is that if tp_dealloc() for one of the affected types tries to free a static object then it will crash. We've set the refcount for such objects to a really high number to avoid this, but it is still possible. The risk rises a bit for immortal objects (see PEP 683).

For all types with static objects, we need to add a check in tp_dealloc() to either fail or reset the refcount to the really high number. We already have a check like this for the singletons and for str. For the other types we need to identify if the object is static and respond accordingly. The catch is that identifying that can be expensive, which is problematic for types that are deallocated frequently.

Inizia da Include/internal/pycore_global_objects.h per inventariare gli oggetti definiti staticamente, quindi esamina le implementazioni di tp_dealloc dei tipi interessati. Determina come ogni tipo possa identificare gli oggetti statici senza un overhead di deallocazione inaccettabile; il lavoro è completo quando gli oggetti statici non possono essere liberati né causare un crash correlato a refcount.