`_PyTrash_begin` and `_PyTrash_end` do not have implementation

[sobolevn]

We only have this left for _PyTrash_begin and _PyTrash_end:

~/Desktop/cpython2  main ✗                                                                
» ag _PyTrash_begin .
Misc/NEWS.d/3.9.0a5.rst
1217:PyThreadState attributes, but call new private _PyTrash_begin() and

Include/cpython/object.h
479:PyAPI_FUNC(int) _PyTrash_begin(PyThreadState *tstate, PyObject *op);

» ag _PyTrash_end .  
Misc/NEWS.d/3.9.0a5.rst
1218:_PyTrash_end() functions which hide implementation details.

Include/cpython/object.h
480:PyAPI_FUNC(void) _PyTrash_end(PyThreadState *tstate);                  

Source:

cpython/Include/cpython/object.h

Lines 478 to 481 in 313b96e

	/* Python 3.9 private API, invoked by the macros below. */
	PyAPI_FUNC(int) _PyTrash_begin(PyThreadState *tstate, PyObject *op);
	PyAPI_FUNC(void) _PyTrash_end(PyThreadState *tstate);

They don't even have implementations. Looks like that they used to be called from Py_TRASHCAN_BEGIN and Py_TRASHCAN_END in 3.9:

cpython/Include/cpython/object.h

Lines 520 to 545 in 340a82d

	PyAPI_FUNC(int) _PyTrash_begin(struct _ts *tstate, PyObject *op);
	PyAPI_FUNC(void) _PyTrash_end(struct _ts *tstate);
	#define PyTrash_UNWIND_LEVEL 50
	#define Py_TRASHCAN_BEGIN_CONDITION(op, cond) \
	do { \
	PyThreadState *_tstate = NULL; \
	/* If "cond" is false, then _tstate remains NULL and the deallocator \
	* is run normally without involving the trashcan */ \
	if (cond) { \
	_tstate = PyThreadState_GET(); \
	if (_PyTrash_begin(_tstate, _PyObject_CAST(op))) { \
	break; \
	} \
	}
	/* The body of the deallocator is here. */
	#define Py_TRASHCAN_END \
	if (_tstate) { \
	_PyTrash_end(_tstate); \
	} \
	} while (0);
	#define Py_TRASHCAN_BEGIN(op, dealloc) \
	Py_TRASHCAN_BEGIN_CONDITION(op, \
	Py_TYPE(op)->tp_dealloc == (destructor)(dealloc))

But, they are unused since #117763 in ~3.11

What should we do?

1. Nothing
2. Remove them
3. Raise deprecation warning when they are called (but they return void, it would be hard to do)

CC @markshannon @vstinner

Linked PRs

• gh-128910: Remove _PyTrash_begin and _PyTrash_end C-API functions #128919

[vstinner]

Please remove them. It's misleading to announce that we have two functions which they don't exist!

There is no backward compatibility concerns since this API is excluded from the limited C API / the stable ABI.