[issue46895] Type-Modified Callbacks

[Matt Page]

New submission from Matt Page <mpage at cs.stanford.edu>:

CPython extensions providing optimized execution of Python bytecode (e.g. the Cinder JIT), or even CPython itself (e.g. the faster-cpython project) may wish to cache access to lookups in the class hierarchy (e.g. when resolving the target of a method call). Extensions that perform these optimizations need to know when to invalidate the cached values. CPython already has a mechanism to invalidate its internal state (e.g. the global method cache) when a type is modified: _PyType_Modified. We propose adding an API to allow extensions to set a callback that will be invoked by _PyType_Modified whenever a type, or any ancestor of the type in the class hierarchy, changes.

Proposed API:

```
// A callback to be invoked with the modified type and optionally the name of
// the attribute that was modified.
typedef void(*PyType_ModifiedCallback)(PyTypeObject* type, PyObject* attr);

// Set or get the callback. The callback may be cleared by supplying a NULL callback.
void PyType_SetModifiedCallback(PyType_ModifiedCallback callback);
PyType_ModifiedCallback PyType_GetModifiedCallback();
```

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components: C API, Interpreter Core
messages: 414305
nosy: carljm, dino.viehland, itamaro, mpage
priority: normal
severity: normal
status: open
title: Type-Modified Callbacks
type: enhancement

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46895>
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