Bug(ish?) report

The following function has a cache. If you are using a factory to call ctypes.POINTER in a loop, the memory usage is unbounded and unable to be reclaimed.

https://docs.python.org/3/library/ctypes.html#ctypes.POINTER

The documentation should mention that this is unbounded and should not be called in a loop, or the cache should be changed to a configurable, bounded LRU cache.

Example of a variable length type factory used by windows, and a bad func that cannot be called in a loop:

def shitemid_factory(size: int) -> Type[ctypes.Structure]:    class SHITEMID_Var(ctypes.Structure):        _fields_ = (            ("cb", USHORT),            ("abID", BYTE * size),        )    return SHITEMID_Vardef bad_func():    SHITEMID_Var = shitemid_factory(sz - ctypes.sizeof(USHORT))    item_var = ctypes.cast(item_ptr, ctypes.POINTER(SHITEMID_Var))

Linked PRs

• gh-100926: Move ctype's pointers cache to StgInfo #131282
• gh-100926: fix thread safety ofctypes__pointer_type__ #133843
• gh-100926: use explicit stginfo lock for pointer cache #133867