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Merged
merged 1 commit into from
Jun 23, 2021
Merged

bpo-39947: Remove old private trashcan C API functions #26869

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16 changes: 2 additions & 14 deletions Include/cpython/object.h
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Expand Up @@ -493,8 +493,8 @@ without deallocating anything (and so unbounded call-stack depth is avoided).
When the call stack finishes unwinding again, code generated by the END macro
notices this, and calls another routine to deallocate all the objects that
may have been added to the list of deferred deallocations. In effect, a
chain of N deallocations is broken into (N-1)/(PyTrash_UNWIND_LEVEL-1) pieces,
with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
chain of N deallocations is broken into (N-1)/(_PyTrash_UNWIND_LEVEL-1) pieces,
with the call stack never exceeding a depth of _PyTrash_UNWIND_LEVEL.

Since the tp_dealloc of a subclass typically calls the tp_dealloc of the base
class, we need to ensure that the trashcan is only triggered on the tp_dealloc
Expand All @@ -503,16 +503,6 @@ partially-deallocated object. To check this, the tp_dealloc function must be
passed as second argument to Py_TRASHCAN_BEGIN().
*/

/* This is the old private API, invoked by the macros before 3.2.4.
Kept for binary compatibility of extensions using the stable ABI. */
PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
PyAPI_FUNC(void) _PyTrash_destroy_chain(void);

/* This is the old private API, invoked by the macros before 3.9.
Kept for binary compatibility of extensions using the stable ABI. */
PyAPI_FUNC(void) _PyTrash_thread_deposit_object(PyObject*);
PyAPI_FUNC(void) _PyTrash_thread_destroy_chain(void);

/* Forward declarations for PyThreadState */
struct _ts;

Expand All @@ -522,8 +512,6 @@ PyAPI_FUNC(void) _PyTrash_end(struct _ts *tstate);
/* Python 3.10 private API, invoked by the Py_TRASHCAN_BEGIN(). */
PyAPI_FUNC(int) _PyTrash_cond(PyObject *op, destructor dealloc);

#define PyTrash_UNWIND_LEVEL 50

#define Py_TRASHCAN_BEGIN_CONDITION(op, cond) \
do { \
PyThreadState *_tstate = NULL; \
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20 changes: 20 additions & 0 deletions Misc/NEWS.d/next/C API/2021-06-23-10-31-45.bpo-39947.je_HMo.rst
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@@ -0,0 +1,20 @@
Remove 4 private trashcan C API functions which were only kept for the backward
compatibility of the stable ABI with Python 3.8 and older, since the trashcan
API was not usable with the limited C API on Python 3.8 and older. The
trashcan API was excluded from the limited C API in Python 3.9.
Comment on lines +1 to +4
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Could you say which ones?

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Sure, done.


Removed functions:

* _PyTrash_deposit_object()
* _PyTrash_destroy_chain()
* _PyTrash_thread_deposit_object()
* _PyTrash_thread_destroy_chain()

The trashcan C API was never usable with the limited C API, since old trashcan
macros accessed directly :c:type:`PyThreadState` members like
``_tstate->trash_delete_nesting``, whereas the :c:type:`PyThreadState`
structure is opaque in the limited C API.

Exclude also the the ``PyTrash_UNWIND_LEVEL`` constant from the C API.

Patch by Victor Stinner.
12 changes: 0 additions & 12 deletions Misc/stable_abi.txt
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Expand Up @@ -1602,12 +1602,6 @@ function _PyThreadState_Init
function _PyThreadState_Prealloc
added 3.2
abi_only
function _PyTrash_deposit_object
added 3.2
abi_only
function _PyTrash_destroy_chain
added 3.2
abi_only
data _PyWeakref_CallableProxyType
added 3.2
abi_only
Expand Down Expand Up @@ -1920,12 +1914,6 @@ function Py_EncodeLocale
added 3.7 # (and 3.6.1 and 3.5.3)
function Py_SetPath
added 3.7 # (and 3.6.1 and 3.5.3)
function _PyTrash_thread_deposit_object
added 3.7 # (and 3.6.1 and 3.5.3)
abi_only
function _PyTrash_thread_destroy_chain
added 3.7 # (and 3.6.1 and 3.5.3)
abi_only
function PyErr_SetExcFromWindowsErr
added 3.7 # (and 3.6.1 and 3.5.3)
ifdef MS_WINDOWS
Expand Down
56 changes: 8 additions & 48 deletions Objects/object.c
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Expand Up @@ -2092,25 +2092,13 @@ Py_ReprLeave(PyObject *obj)

/* Trashcan support. */

/* Add op to the _PyTrash_delete_later list. Called when the current
#define _PyTrash_UNWIND_LEVEL 50

/* Add op to the gcstate->trash_delete_later list. Called when the current
* call-stack depth gets large. op must be a currently untracked gc'ed
* object, with refcount 0. Py_DECREF must already have been called on it.
*/
void
_PyTrash_deposit_object(PyObject *op)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
struct _gc_runtime_state *gcstate = &interp->gc;

_PyObject_ASSERT(op, _PyObject_IS_GC(op));
_PyObject_ASSERT(op, !_PyObject_GC_IS_TRACKED(op));
_PyObject_ASSERT(op, Py_REFCNT(op) == 0);
_PyGCHead_SET_PREV(_Py_AS_GC(op), gcstate->trash_delete_later);
gcstate->trash_delete_later = op;
}

/* The equivalent API, using per-thread state recursion info */
void
static void
_PyTrash_thread_deposit_object(PyObject *op)
{
PyThreadState *tstate = _PyThreadState_GET();
Expand All @@ -2121,37 +2109,9 @@ _PyTrash_thread_deposit_object(PyObject *op)
tstate->trash_delete_later = op;
}

/* Deallocate all the objects in the _PyTrash_delete_later list. Called when
* the call-stack unwinds again.
*/
void
_PyTrash_destroy_chain(void)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
struct _gc_runtime_state *gcstate = &interp->gc;

while (gcstate->trash_delete_later) {
PyObject *op = gcstate->trash_delete_later;
destructor dealloc = Py_TYPE(op)->tp_dealloc;

gcstate->trash_delete_later =
(PyObject*) _PyGCHead_PREV(_Py_AS_GC(op));

/* Call the deallocator directly. This used to try to
* fool Py_DECREF into calling it indirectly, but
* Py_DECREF was already called on this object, and in
* assorted non-release builds calling Py_DECREF again ends
* up distorting allocation statistics.
*/
_PyObject_ASSERT(op, Py_REFCNT(op) == 0);
++gcstate->trash_delete_nesting;
(*dealloc)(op);
--gcstate->trash_delete_nesting;
}
}

/* The equivalent API, using per-thread state recursion info */
void
/* Deallocate all the objects in the gcstate->trash_delete_later list.
* Called when the call-stack unwinds again. */
static void
_PyTrash_thread_destroy_chain(void)
{
PyThreadState *tstate = _PyThreadState_GET();
Expand Down Expand Up @@ -2192,7 +2152,7 @@ _PyTrash_thread_destroy_chain(void)
int
_PyTrash_begin(PyThreadState *tstate, PyObject *op)
{
if (tstate->trash_delete_nesting >= PyTrash_UNWIND_LEVEL) {
if (tstate->trash_delete_nesting >= _PyTrash_UNWIND_LEVEL) {
/* Store the object (to be deallocated later) and jump past
* Py_TRASHCAN_END, skipping the body of the deallocator */
_PyTrash_thread_deposit_object(op);
Expand Down
4 changes: 0 additions & 4 deletions PC/python3dll.c
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Expand Up @@ -37,10 +37,6 @@ EXPORT_FUNC(_PyObject_NewVar)
EXPORT_FUNC(_PyState_AddModule)
EXPORT_FUNC(_PyThreadState_Init)
EXPORT_FUNC(_PyThreadState_Prealloc)
EXPORT_FUNC(_PyTrash_deposit_object)
EXPORT_FUNC(_PyTrash_destroy_chain)
EXPORT_FUNC(_PyTrash_thread_deposit_object)
EXPORT_FUNC(_PyTrash_thread_destroy_chain)
EXPORT_FUNC(Py_AddPendingCall)
EXPORT_FUNC(Py_AtExit)
EXPORT_FUNC(Py_BuildValue)
Expand Down